Wont start after installing blower motor resistor.

DBill 06 TB LS

Original poster
Member
Dec 6, 2015
8
Oklahoma City
2006 Trailblazer LS

Finally went in to replace the blower motor resistor that went out over the summer, because its getting frosty in Oklahoma now and I need the defroster to work. Found many guides to do so, and successfully replaced the resistor (all fan speeds now work great when ignition is turned to [ON]).

To my knowledge, i was having no other issues but after getting the new resistor hooked back up, the car will no longer start. Battery was just over 5 years old, so I had it tested and replaced. Have gone through every fuse with a test light, and have checked the relays and replaced them as well.

I can get the starter to engage fully by bypassing the relay, but the vehicle will not stay running.

As I said, the vehicle ran fine earlier during the day before i changed out the blower motor resistor, and every standard check seems to tell me everything is ok. Aside from it not starting.

All the proper interior controls work when the key is placed in the corresponding ignition switch position, and all of the fuses look in good condition and are getting power.

So I'm starting to run out of ideas for things to check, and would really appreciate some help.

What started as a 30-45 minute resistor swap has turned into a weekend full of headaches that just raise more questions.
 

Mooseman

Moderator
Dec 4, 2011
25,184
Ottawa, ON
That's like changing your oil and the wipers stop working. Completely unrelated. So something is preventing it from starting. Is the security light on? Maybe something in the wiring got disturbed. Did you go under the dash on the driver side at all?
 

DBill 06 TB LS

Original poster
Member
Dec 6, 2015
8
Oklahoma City
[QUOTE=" Maybe something in the wiring got disturbed. Did you go under the dash on the driver side at all?[/QUOTE]

The only thing I did under the driver side was after the fact, in using a test light to see if all the connections on my ignition switch were responding correctly, which they did. Other than that it had looked like I lucked out, as I have heard and seen horror stories of the connector wires for these blower motor resistors shorting and frying out all the way up behind the steering column. Every bit of scorched wire on the connector was localized within the first 1/4 inch coming off the resistor, and had been out for months without causing any other electrical issues.

Only other thing I had done recently, was 2-3 weeks ago changing out a camshaft sensor which had blown a code (110,000ish miles) and was burned up when I had removed it. But this replacement also went well, and the car had been driving much nicer since changing that out.
 

mrrsm

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With the sudden colder change in ambient temperature and now knowing that with a 110K Miles... your vehicle is no Spring Chicken and since you live where it gets cold...things wear out much faster in extremes of temperature... Have you considered what @Mooseman mentioned about "Not Mixing Your Mechanical Metaphors"...so to speak? In other words... find out if its just a "coinkadink' that the STARTER just happened to go T*tz Up around the same time you were working on your heater blower motor issues.

I know... It is a PITA to have to pull the starter because you have to jack up and Jack Stand the vehicle and then pull off the Driver's Side Wheel and then clean the wheel liner good enough to tape the viewing flap on the inner panel up and duct tape it out of your field of view. and on and on...

Also... @Mooseman has also made many posts about the strange behaviors of the Ignition Switch that is often the weak link in many other electrical problems and he has posts and procedures for changing out that switch. Just for now... at least until a wiser head than mine can suggest anything else... look at the @Mooseman "HowTo R&R the Ignition Switch" and perhaps get a good price on a Duralast Starter...throw both of them in there and see what happens. You really won't be out of anything if it turns out to be something else because you are due for a new starter and the new IS will prevent other Mechanical Bogeymen from crawling out from under the bed as winter sets in.
 

DBill 06 TB LS

Original poster
Member
Dec 6, 2015
8
Oklahoma City
I don't mind swapping those out if it needs to happen, but I'd rather not blindly throw money into it. As I said, I did test the ignition switch with a tester, and by checking which controls in the cabin responded with keys in appropriate position in the ignition cylinder.

Wondering if its not just a shot out PCM, since the starter itself will fire up after jumping the relay. Because it seems like if the starter or solenoid were bad, it wouldnt respond so immediately by simply jumping the relay and forcing juice into it.
 

DBill 06 TB LS

Original poster
Member
Dec 6, 2015
8
Oklahoma City
Also did have the relays bench tested for continuity, and they failed, so I replaced them. I suppose it is a possibility that the new relays may have come out of the box faulty.
 

mrrsm

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mrrsm

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I watched a few of the more electronically gifted techy videos on tearing apart the Ignition Switches on a 2003 Chevrolet Silverado... and the bottom line was that the Dude said, "I cannot find anything wrong with this complex switch...and yet it STILL does not work..." So it might be the same with yours... I mean really... how many time have have you turned your ignition key On and Off since you have owned your TB? 1,000?...10,000? Who know what subtle problems it has as soon as it get puts back in. (Shades of Dave Bowman)


Please forgive me for being a bit blunt... but at this point... trying to chase down the micro-glitches that will inevitably involve changing one or all of these related components... is bit like trying to "Separate Fly Sh*t from Pepper". I appreciate the logical progression of what you want to accomplish... but at some point ... the best way of solving these weird problems is to eliminate the places where they cluster. The Ignition Switch, Fuseable Links and PCM are the same such places.
 
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DBill 06 TB LS

Original poster
Member
Dec 6, 2015
8
Oklahoma City
Plenty fair enough, and don't worry about being blunt. I never got a participation trophy i didn't burn. I'll go ahead and get the new relays tested just to be sure, and pick up a new ignition switch while I'm at it. If this doesn't clean up the problem, I'll go ahead and order a new PCM.

Everything will still end up being about as much or less than it would have been to take the car to the dealer to get the resistor changed in the first place. So i can't complain too much.
 
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mrrsm

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I was just wondering of you followed any of this information while doing your repair?

http://gmtnation.com/forums/threads...otor-resistor-pack-and-connector-pigtail.2961

If so... perhaps you cut an additional wire or two without realizing the problem. It seems very easy to do when unraveling what looks like a "Bag of Snakes" and while handling "Sharps" that can easily nick wires here and there. I don't have any knowledge of how to bench test a PCM... but since you were pulling perhaps on some wires under the dashboard area when working on the resistor issue at adjacent harness wires might have been touched, it would not hurt to unbolt all the PCM harness connectors and check to see if their "O"ring gaskets are intact and unfolded and then bolt them back up and try to start the vehicle. Since you cannot do a Specific Gravity Test on your 12 Volt battery... you should consider replacing it if you have any doubt of its power. Since you seem to understand circuitry in general... it might be helpful to find a vehicle wiring diagram and trace out the most basic straight line possible from the Key-ON circuit...all the way through to the Starter Motor and see if there is anything that we missed. One last thing to check is to find the bolt down grounding circuit where all of your Fuse-able Links converge on the vehicle frame and after taking the Negative Ground Cable loose from the battery, unfasten that bundle and clean the various flat connectors and re-fasten them all down to make certain you have a good ground for everything. check all of the Braided Copper Bonding Straps between the Engine Block and the Frame...for looseness or corrosion and securely re-attach them. Re-attach the Negative Ground Wire and try using your back-Up Ignition key to see if the switch will behave differently and allow the engine to turn over.

Okay.... there is one other off-the-wall method that can ruin a PCM ...and I am not speculating here... I know this happened for a fact. They make a device called a "Rat Zapper" that is basically a battery powered electronic device capable discharging a powerful storage capacitor with sufficient instantaneous voltage and amperage to electrocute any rodent that steps inside the trap to eat the bait and triggers it to fire. Of course, the rodent is killed instantly and cleanly as if it were struck by a bolt of lightning. Unfortunately, an uninvited by-product of the discharge comes in the form of a Very Powerful EMP (Electro-Magnetic-Pulse) that propagates outwards like an electrical donut...and is sufficiently powerful enough to destroy the micro-circuitry in any ECM or PCM close enough (say in an enclosed garage) to be within reach of its valence. This device can instantly destroy any of modern Mini-Fluorescent screw-in type bulbs as well. I do not think that our PCMs are shielded by means of a Faraday Cage... and I realize that it seems odd to ask...but...do you have any such device around your vehicle? If not... the only other thing I can think of is that the $99.00 PCM is probably still available on eBay and it would be a fraction of the cost of buying a brand new one.
 
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Mooseman

Moderator
Dec 4, 2011
25,184
Ottawa, ON
For checking if the PCM is dead or otherwise, did you try hooking up a code scanner and see if you can communicate with it? And you didn't answer my question about the security light.
 

Robbabob

Member
Dec 10, 2012
1,096
Bypass the resistor pack and it works fine.... How do you bypass this? You either plug it in to work the fan or you unplug it to not work the fan. What am I missing?
 

mrrsm

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