Converting to e-fans (full-size pickup / GMT800)

[Reprise]

(Attention: After a 3hr drive, almost a year after installing this, I found out the harness I reference below... melted the relay plug / connectors -- which I only noticed after I almost fatally overheated the engine). Link HERE for more info... and I recommend against purchasing that particular harness. I'm ordering one from Nelson Performance as a replacement. Lesson Learned... )


So... I've been offline for a bit; maybe we'll subtitle this thread "What I did over my summer vacation"

(Note: This is going to be in at least two parts, as GMTN has a 10K character limit per post, and I know I'm > 15,000 already)

Covers:

99-06, 07 'Classic' GMT800 series
(photos show a P59 ECM; others similar)

During a P/S pump replacement, I decided to do the e-fan conversion since I was taking out so much stuff in the same area. These are found on the '05-up trucks, but can be retrofitted as far back as '99.

As for what you'll need...

A 34” core radiator (these are mostly found in 3/4-ton series – basically, anything with a 6.0L installed. They also should have the bungs for the oil cooler lines on the driver side (and you don't need to run lines to these; blockoff plugs are just fine, if you're not ready to install the oil cooler lines between the block mount location (just above the oil filter, sealed with its own blockoff plate, by default on the 5.3L and smaller V8s).

If you have a 1/2-ton 1500, your radiator has a 28” core, and you'll need to upgrade it in order for the new fan assembly to fit, as the assembly is too large, otherwise (and you'll need to be creative in mounting it. With the larger rad, it's a drop-in affair.

A fan harness with in-line relays to turn the fans on / off at the appropriate times. You can either order the GM part, or an aftermarket solution. Nelson Performance probably makes the best version, but they're expensive (triple the $ of what you find on Amazon). I went with the highly-rated Amazon solution.

The fan assembly. I went with an aftermarket from Rock that had a lifetime warranty. Note there are two versions – one has a 5- and 7-blade, the other has a 7- and 9-blade. Ostensibly, the 7&9 blade option is better, if you can find it.
Mine is the 5&7 combo.

A way to program your ECM fan controls. The ability is built into the P59 ECM, but turned off on the pickups before '05, because they use the mechanical fan / clutch. It's a simple matter to turn it on with HP Tuners (I'll include a screenshot or two for reference). If you don't have HPT, resources like Limeswap and ECM 4 Less are available on a mail order basis, and whomever you have locally. Yes, I can do it for you, but you'll need to purchase license credits, as my licensure with HPT is currently on a per-truck basis. PM me for more details. But I'd go with Jeremy @ Limeswap, if you want more than the fans activated. Also, return visits for your ECM with him are only $25 (as of this writing), if you want more done later.

If you have an alternator rated at less than 130A, seriously consider upgrading it to a 130A or 145A, if possible. These fans use a lot of juice (up to 40A each), and if your alternator is rated on the small side, you may find it working harder to keep up.

To start, disco the battery, and remove the upper shroud. If you need help on how to do this, stop here, save yourself a lot of trouble, and have someone do this for you. But almost everyone here knows their way around a vehicle, so...

Remove the mechanical fan / clutch. LEAVE the serpentine belt on until you get the nut loose, as it will help hold the fan stationary. If it's been a long time (or never) since the fan / clutch retaining nut has been removed, it's going to be a bit of a struggle to get it off. But it can be done (and there are plenty of tutorials available here and elsewhere). For one that's stuck on, an air hammer with the flat chisel attachment will make quick work of the job (focus on the left side of the nut, as you're facing it.) If you don't have an air compressor, you can also get it off with a cold chisel / hand sledge, or a pipe wrench. Just make sure the pulley is immobilized, and you'll get it off. If you've had the fan / clutch off beforehand, it should be a LOT easier to get the thing off, as long as you didn't torque it back on the last time you had it off (which is never needed, anyway, as centrifugal force tightens it once you start the engine.)

With the fan / clutch removed, you'll have enough room to remove the lower shroud. Notice that I didn't mention draining coolant / disconnecting radiator hoses? That's because you don't have to. It'll take a bit of fiddling, but you can get it out (in my case, I was able to go from underneath, and twist / turn it so that it came up through the passenger side opening. In my case, I think I still had the fan on, even – but if you can remove it, it'll make it that much easier, of course. For that reason, you can probably leave the serpentine belt attached, as well, if your project is starting / ending with this mod.

With the upper fan shroud and the mechanical fan / clutch removed, you should have plenty of room to remove the ECM from its housing, and disconnect the two harness connectors (you'll need a 7mm socket for the center retaining bolt). If you haven't disconnected the battery yet, do so, before touching the ECM. The last thing you want to do is to short out & have to replace the ECM.

Now, with the two harness connectors removed, you'll need to remove the retainers on both sides, in order to reach the pinouts. For the outer (large gray) retainers, take a pair of pliers, and squeeze the tabs on the ends inward, then lift them up and off. There are also locking tabs along both of the long sides; press inward to release them. These aren't as flexible as the end connectors, so use a bit more care, if you don't want to crack off the tabs.


Removing the outer retainers. You may need to rock them a bit, but they'll come off without too much trouble.


Now, with the outer retainers off, you can remove the colored inner connectors using a pick tool, by pressing inward on the locks on the ends. Here's a couple of pics of where they're at:



Locations of the inner pin cover lock releases (push inward on the center white sections)

With the covers removed, you'll see the pins embedded in the connector.
You're now looking for the following locations (one on each larger bank):

Blue – pin 42 (on schematics, the Blue connector is also referred to as 'C1')

Green (or Red) – pin 33 (and this one is 'C2', of course)

(if you are making a harness from scratch, you'll need Micro-Pack 100W 1.0 Terminals for the ECM end, and you should use 18-20ga wire. But if you're rolling your own, you know this, too)

The ECM actually has tiny numbers above or below each terminal on the back end of the mounting 'plug'. But for those of us with tired eyes, here's the layout of the connector:


So, from the above layout, the wire for the blue connector goes into the top row, 2nd from the left

The other wire goes into the OTHER connector, and pin '33' is on the bottom right row, 7th from the right.

You're advised to use some silicone spray to insert the pins. Don't be stingy. The connections are tight, and if you're not careful, it's *super* easy to break off a pin. Ask me how I know. Here's some more recommendations, from me, as I found this to be the most difficult part of the project:

Usually, the two ECM connection wires are pre-terminated, but temporarily fastening the main power & ground connections (ring terminals) can help hold the harness in place, while you make these connections. Being small, they can be a PITA to work with.
Take a straight pick or small awl, and give the socket a decent reaming, from both ends. If you do this right, you'll see a little bit of the rubber be pushed out of the socket (white colored, on the blue connector, and red colored, on the green / red). That's fine; just clean out the particles that are ejected. After a couple of reamings, you'll notice there's less resistance when you insert the pick. That's what you want, so ream away.

The 'inside' end has tiny plastic 'fingers' to lock the micro-pack pin into place. You can lift these up to make it easier to get the pin inserted fully (which will require insertion past the end of the metal pin; about 1/8” or so. If the wire bends, it will be nearly impossible to get it pushed into the connector. Using the flat end of one of the tools I mention below as a brace, to keep the wire straight, can help.
One source I read about on these suggested pushing the wire through, before adding the micro-pack connector pin (so that you crimp the connector on, then move it backwards to seat). I did try this, but it was difficult to terminate the micro-pack onto the wire, so I went back to the 'conventional' way.
The pins are available from Amazon; I ordered (2) packages of 12 (about $8/ea), and used about six of the (24) total. Most of the offerings are for 50-100 (or more) of these, so look for the small quantity packages.

End of Part 1...

 

[Reprise]

Part 2...

There is a dedicated crimping tool for these micro-pack pins. It runs about $15 on Amazon. Whether you return it after terminating two pins with it is your business. If you have a good quality crimping tool, you may be able to use that, instead. Strip the wire about 3/16”, and place the bare wire section about halfway up the rear side of the pin (you'll see tiny metal 'fingers' on each side; when crimped, they interlock and surround the wire, kind of like a venus flytrap plant). Once secured, then crimp the shielded wire to the end of the connector. If you're using the weatherproof plug at the end (not here), that goes onto the wire before you attach the connector. Amazon has pictures of this procedure, if you're looking at the crimping tool.
There is an additional 3 pc tool set that helps with inserting / releasing the connectors. It runs about $8, and especially if you see yourself adding / removing pins to the 80-pin connector module again at a later time, I'd recommend the spend. A pic of these tools is below. I found them useful, even though I was only adding two pins (for now; I'll also eventually add a 3rd one on 'blue 56' to accommodate an alcohol percentage composition sensor (for flex-fuel; this will be a different write-up)

You'll (barely) hear / feel a slight click when the pin locks into the connector. If you need to remove a pin, there's a lock release on the opposite side (where the colored covers go) – the white plastic 'fingers' I mentioned, earlier.

Once you've got these tiny little pins terminated, inserted, and locked in the ECM connectors, reassemble the covers you removed, and fasten the connectors back onto the ECM. You'll notice labeling on the grey covers stating not to overtighten, so 'snug' is just fine on that little 7mm bolt. Drawing the bolt down is what actually fastens the connector, so don't exert a lot of strength to 'seat' the connector onto the ECM – just make sure things are lined up, and the bolt will do the rest. Also, check that the red rubber surround gaskets are in place, beforehand (they'll likely be inside the connector when you remove it), as these provide a moisture seal.


With the ECM connections made, you can layout the harness routing and secure it as per instructions. If the wires are exposed, use some 1/4” wire loom to provide some protection – because if the wires are compromised, you won't have running fans. At this point, you have four (4) connections to terminate – the main power & ground (ring terminals), the relays (on either the underhood fusebox, or the plastic cover that shields the ECM), and the two plugs for the fans. There are two ground connections; one connects at the 'common' grounding point on the engine accessory bracket. The second ground wire is shorter; if you want to connect it at the same point on the acc'y bracket, you'll need to lengthen the ground wire by about a foot to make it reach that connection. This is what I did, but if you attack it from the opposite end, there's another common ground location by the front bumper, on these pickups. I didn't bother checking before I decided to just lengthen the wire and terminate it up top. Everything else should reach just fine. You should have two 40A fuses inline on the power side; check to see that they're intact).


Leaving the fan assembly out of the truck until now gave me more room to work with the ECM wiring. The assembly will take a little maneuvering, and you may need to go under the truck to line things up, but it should go into place. Check to see that the bottom rides on the lip of the lower bulkhead (my assembly had 3 notched rubber connectors there), and that the side guides line up correctly. Removing the plastic connectors that help hold the trans lines in place so that the lines move more freely while you're working on this). With the bottom & sides lined up, you should find the holes lined up between the fan assembly and the top of the bulkhead. Note that these are different sized bolts (and in a different location than where the smaller 10mm bolts attached the plastic shroud you removed earlier. Transfer the applicable retainers (like for the upper rad hose) to the assembly. The bolts that fasten the assembly to the truck are the same type that fasten the radiator to the bulkhead, so removing one for sizing will help (they're M8 x 1.0 x 23mm, btw, with a washer surround. There's room for a longer bolt, so up to a 50mm length could work here (my hardware store had a 35mm, so I used that)


Here's a pic with everything wired up, zip tied out of the way, etc., along with the fan assembly.

Hmm... there's a fair bit of room now between the fans and the front pulley assemblies / serpentine. Seems like something ought to be there? :😁:


After securing the fan assembly, and making sure your plugs are connected, it'll be time to program the ECM. If you are having someone do this locally, you can temporarily reattach the mechanical fan / clutch in order to drive the truck to your tuner, if needed (there's room, so you don't have to remove the e-fan assembly, or replace the plastic shroud for the mechanical fan). Or... you could temporarily wire both fans to be 'on' 100% of the time, for your drive over to the tuner. Your choice.


(Next up: Pics for above text; ECM programming via HPTuners (new post)

 

[Reprise]

Part 3: Programming / Testing:

With everything wired up, double-checked, etc. … now it's time to program the ECM to recognize and control the fans. Enter... HPTuners (what you see below are screencaps from v.3.6.26; while the 4.x version can be downloaded, it's typically 'beta'. Version 3.x is considered the stable version. Plus, I use the original MVPI v.1 hardware interface (what plugs into the OBD-II port and reads / writes to the ECM).
Here, I have two files open – the one with my configured changes, and the comparison file, with the original settings. The fields that are different show up with the parameter headings in Green (so, basically, you're updating everything on this screen except for the 'Desired % vs ECT' section. I'll show that in a bit, just for reference.

Note that these are 'ballpark' settings, and can be adjusted – I fully intend on tweaking a couple of them once I've spent time in various towing states that I haven't been able to check, yet. Also, these might be considered a little 'conservative' (or 'aggressive', depending on what you want to call turning on the fans a little sooner than absolutely necessary, which is what I'm doing here.)


Screenshot of HPTuners e-fan configuration (P59 ECM). The On / Off temps can be played with a bit, if you run a cooler t-stat, etc. Note that some of these conditions overlap; the ECM will determine best conditions and select parms accordingly. I left the 'Control By %' table alone – this determines 'how much fan percentage' to activate, vs. ECT. It doesn't come into play until things start getting relatively hot (in vehicles with a thermally operated clutch only; makes no difference with a mechanical / fixed temp fan clutch).

You'll also need to check A/C settings on the next tab (below); 'Serial Cycling' is an important parm on the '03-up trucks, so make sure it's chosen (99-02 trucks are a little different, and I'm leaving that out for brevity, plus the info is readily available on the web).



Finally, here's what the 'Desired % vs ECT' table looks like (you don't need to change this; I'm just showing it for reference / those curious):



Note that the fan isn't even commanded 'on' until 221F or higher, starting at 10%

With the fan programming in, save your file with a new file name (this allows you to preserve the 'before' settings, if you ever need to reference them, or want to go back to your OEM fan config.)

If you have an aftermarket radio, pull the fuse, or HPTuners may appear to brick the ECU (no sense getting in a panic). If this happens, reset by disconnecting the battery, and retry – it should write fine, with your sound system taken off the bus, which is why it 'pseudo-bricks' – the write expects to communicate with the OEM radio, over the bus.

With the write committed, use the HPT logger program to check fan operation (you can dynamically command the fans on, like with a GM Tech 2, or take the truck on a run and ensure the fans turn on / off as you set them. I did the latter; here's what that looks like:



The first channel grouping (through 'AC Active') is what you'll want to select. Note that 'Fan 1' and '2' are 'on' / 'off' binary, as well as 'AC Active' ('yes', 'no'). The channels below that group are just 'leftovers' from a prior config I had. If you want to add gauges, those are on the right (although I didn't get the two 'fan' gauges running correctly; you can probably figure out why

Below is a capture from a moment in time showing the active readings:





Finally, if you want to know how GM's logic operates these fans, here's the rundown (copied from another source, not 'me'). Remember, you can alter these parms, as I showed above...

Cooling Fan Control - Two Fan System

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan s/p relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM supplies a ground path for the high speed fan relay and the cooling fan s/p relay through the high speed cooling fan relay control circuit. This energizes the cooling fan s/p relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

Important: The right and left cooling fan connectors are interchangeable. When servicing the fans be sure that the connectors are plugged into the correct fan.

The PCM commands the low speed cooling fans ON under the following conditions:
Engine coolant temperature exceeds approximately 104.25C (220F).
A/C refrigerant pressure exceeds 1447 kPa (210 psi).
After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 101C (214F) the low speed fans will run for a minimum of 60 seconds After 60 seconds, if the coolant temperature drops below 101C (214F) the fans will shut OFF. The fans will automatically shut OFF after 3 min. regardless of coolant temperature.

The PCM commands the high speed fans ON under the following conditions:
Engine coolant temperature exceeds approximately 107.2C (225F).
A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
When certain DTCs set.

At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed if required. This insures idle stability by preventing the fans from cycling between high and low speed.

So... that's the programming and testing, for your review.
Next: My evaluations / conclusions, benefits (real / imagined) , as well as what this little adventure cost (time and $).

 

[Reprise]

So, after running these for several drive cycles, my thoughts...

- Increased power? Nothing I'd call noticeable, tbh. I noticed more when I removed the Flowmaster muffler the truck came with, and had a quieter one welded on. With that, I noticed the *subtraction* in power, via the butt dyno. Subtle, but it was there.
That said, not having a mechanical fan *should* reduce parasitical loss both through its presence, and (mostly) when it's activated. 'Should' is the operative word.

- Cooling improved? Well, it's not *worse*. But ambient temps have been cooler lately, too. Because I can play with the on / off temps & conditionals a bit, I'll reserve judgement for now. But this was mostly the point behind doing it, so...
From what I understand, these fans are each capable of 10,000 cfm. That's a *lot* of air. And I believe it, because...

- These fans are LOUD. You can actually hear the 1st one running *in the cab*, unless you've got your tuneages playing loudly. Since I'm not usually listening to music, I can hear them without too much trouble.

- At 40A for each fan, plus a 3rd 40A relay when they both come on.... these *do* draw some juice. I have a 145A alternator, which for 2003, was considered on the 'large' side, since my truck is built to 2500HD spec and in a fairly high-level trim (power seats, heated seats, etc., etc.) But after install, I see my amperage gauge has gone from just on the 'plus' side of 14V, to two 'ticks' under 14V (or, roughly, 13V), at idle. I could have hooked up something to get a digital readout, but never remembered to do that when I was in the truck.
The other thing I now notice in this area is that I can hear the alternator pulley (?) squeaking intermittently. Not sure if that's because I had the belt off, as well as the alternator pulled, so it may be just slightly out of alignment, or if the alternator is squeaking because it's working harder. But if it starts having trouble, I'll probably get one with higher output to replace it. I have one I can use as a spare, on an 'emergency' basis, as well. So I'm not too worried here, given where it sits on the accessory drive (at the top; I could probably R&R one in about 15min, tops). I'd estimate a 165A alternator minimum would be needed, based on what I see.

- Fuel economy: This is supposed to return +1.x mpg. I haven't noticed it yet, but I need to get a couple of full tanks consumed, in order to quantify. On the iMPG display, I'm not noticing much of anything. But I'll also admit that it's very tempting to "give 'er", as our Canadian friends say (e.g.; I'm not really driving for fuel economy, a lot of the time.)

- Cost:
You need the fans, the harness / relays, and a tune (unless you get a fixed temperature probe, which I'm told don't always work too well, and certainly isn't configurable).

I spent about $250 on the fans & harness, and installed them myself. For the tune, I already had a copy of HPTuners, so I had no extra cost, there. If you had to purchase, or had a shop put in the tune (which you can see, isn't too terribly hard)... figure $200-400 or more, depending on what version of HPTuners you got, along with 'how many licenses', or just paid a shop to do it.
Oh, and I also spent about $10 or so on a package of the Micro-Pack connectors I mentioned, $8 (?) on the pack of 3 small tools, and $15 on the special crimper. So roughly another $35 on top of what I mention above.
I also didn't have to spend $ on a larger radiator, as I already had the 34", stock.

All-in... about $285 or so, for me, which makes for a pretty lengthy ROI, if you're calc'ing from gas savings, alone. And I suppose I'll never need to replace the mechanical fan clutch again, if I keep this, so that *could* factor in, I suppose.

- Time: I'm always a bad resource here, because I work very leisurely, compared to others here. If I had everything in the way of tools, connectors, etc., at my side, without having to stop / order / wait for delivery... I'd probably estimate 1/2 a day or so, with all except 1.5hrs going to the physical install, and the 1.5hrs going to tuning activities. Time that I spent researching the solution should also be added in; I didn't compose these posts 'from memory'. What I wanted here was "all" the info regarding these in one site / thread. That, I think and hope (?) I've accomplished.

Would I do it again? Well, I don't have much of a baseline to judge against. For now, I'll say that it wasn't wasted effort, at least. And it does provide some extra room in the engine bay, for... future... mods?
All I can say is... there's more to come for this truck. #NotDoneYet

 

[littleblazer]

The 10 with the 6.2 has what'd I'd assume is about the same fan setup. It works. Does it work as well as the 2500 or 03 escalade? Hard to quantify. I can say the MPGs are closer to the work truck than the escalade though which suprised me considering the whole point of the 6.2 and 6 speed was better efficiency...

I will say the factory fan assembly was already replaced in that truck... I've replaced one fan clutch on the 03 at 260k. They're both the same price give or take for the "good" parts. It seems you gain better low speed performance from air with this. I like it for the added room but I'd be curious if it would handle a 2500 at tow.

 

[Reprise]

Your reply spurred some further thoughts...

- My desire to do this stemmed from the supposed +10-15hp that was supposed to be delivered by this mod. MPG increase would be nice, but what I wanted the power.

- I figured out that it was easier to tell the hp difference (decrease) before the truck got its cam upgrade. Once that was in, and (partially) tuned, the truck has more TQ / HP to the point that it's going to take a bigger gain to tell the difference, especially on the butt dyno.

- @littleblazer -- I'll post back for sure once I get some tow miles with this setup, especially in hot ambient temps. Unfortunately, I don't have a 'baseline' with this truck in those conditions, only with the Envoy. And that stressed the 5.3L, for sure (enough to loosen the t-stat bolts and cause a small leak that I didn't find until I got home)

 

[Mooseman]

I have efans on my Avy with the 6.0 and while towing, I saw temps go up above 220f in 85f temp. I don't know if they're not turning on full before that or that efans are just not the thing to tow with. If my attempts to buy a new truck fail, I am contemplating retrograding to a mechanical fan for next year's towing season.

 

[SpitShine_PL]

Sorry for digging this up, but I am curious about the e-fan conversion for a 2002 (it's a K1500 with rear seat A/C controls, so it has the 34-inch radiator already, plus manual A/C controls all around).

According to another writeup I found for a '02 2500HD truck (here: https://www.gmfullsize.com/threads/electric-fans-on-2002-1500hd-with-proper-a-c-control.314065/), 'proper' A/C-dependent control of the e-fan conversion requires repurpising the PCM pin #33. With the stock settings, this pin is assinged to control the recirculation door. Quote, " this exists is to allow the PCM to force the HVAC system to go into recirculate mode whenever the A/C high pressure side gets too high from insufficient cooling air flow over the A/C condenser. While there is still a chance this could happen with the electric fans, this is a much lower probability since you will have quite a bit of air flow over the condenser even at idle with the electric fans. I will give the disclaimer that I am from a northern state where we rarely break 100*F, so you folks down south are on your own. For me (and a good portion of people on the internet) this isn't a concern and this pin should be re-purposed to control the 2nd fan stage without any issues."

Now, the 99-02 trucks only have a A/C high pressure switch wired to the PCM instead of a A/C high pressure sensor like the 2003 and later trucks. This prevents the PCM from controlling the speed of the fans based on A/C load.

As I am getting a harness from Glenn Auto Performance, it is designed to be wired to pin #42 and to the A/C clutch trigger wire (that provides +12V to the compressor clutch to do the cooling magic).
So, using pin #33 would require replacement of the stock A/C high pressure switch with a 2003+ 3-wire A/C pressure sensor. This replacement seems to be purely optional, so I am planning to stick to the default wiring and programming of pin #42 and tapping into the A/C clutch trigger wire to control the e-fan to run whenever the A/C compressor is spinning (and the refrigerant increases the heat output to be taken off with the fans).

Between your post and the source I linked up here, my understanding is that the 99-02 trucks require a different setting in A/C > Hardware > Type Fitted, which would be 'Analog'. Is this correct? What about other settings, meaning the driving speeds to manage the fan on/off commands; do they apply the same to -2002 trucks as for your 2003?

 

[Reprise]

(Don't kick yourself about resuscitating a 2 year old thread; some people come here and wake up threads that are 5, 6, even 8 years old. I've seen longer than that on other forums, too.)

The short answer... I think you've got the gist of it, from a connection standpoint. I remember when I was planning this that I was glad I had an '03-up truck, as I didn't have to account for the A/C clutch trigger wire and could go with the 'standard' ECM 2-pin solution.

From a programming standpoint, I think you're right there, as well. Let me grab a second cup of coffee and check on this, though. I have a copy of Nelson's instructions saved on this laptop, and I've seen reference to the programming differences somewhere else, too (HPT forum -?)

(on edit: Looks like you're right -- 'analog' cycling is what's needed for the '02-down. See HERE for info, especially page '2' of the thread. My link starts at the beginning of that thread)


I saw from your other post that you're going with Nelson's harness. Since I got mine, it works flawlessly, BTW. Was towing this past week in 90F (30C ?) weather, and the gauge was rock steady. Get the $5 add-on for manual control of the fans, if the '02 allows for use of it -- I haven't (needed to) hook it up yet, but I'm glad I have the option. I hate spending more than needed on something, but the guy at Nelson got it right, and all of the Chinese knock-offs got it wrong, IMHO.

 

[SpitShine_PL]

Thanks!
Will follow the screenshots for setting up the values with HPTuners and go fine tuning from there.
I'll post more in my original thread, as the Nelson harness is now with UPS in my country (should have it by tomorrow, yay!).
(The thread of mine: https://gmtnation.com/forums/thread...2002-gmt800-the-right-tune.23619/#post-637781)

 

[Reprise]

Good luck! If you fine-tune further (I didn't have to), don't narrow the temp delta between 'fan 1' and 'fan 2' activation too much. There's another thread on the HPT forum recently where someone did that and it caused a problem (he had it down to only about 5F before fan 2 kicked on, thinking 'more is better' (typical, right?))

 

[SpitShine_PL]

Will consider this for sure!
Now I got another issue on my hand... Gotta crawl under the Burb and find out why there's a drop of fluid hanging from one of the transfer case bolts. Oh dear!