HVAC problems

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
Burnt out lights in modules and gauges is very common. Doesn't affect operation, just annoying. Most of us just take them apart and replace with LED's except the manual ones are a PITA to take apart because of those slide knobs.

Getting a new one would probably not be any better since you would have to take it to a dealer or someone with a Tech 2 to program it. These are not high failure items but not unheard of. If mode isn't working and two different control heads didn't fix it, likely it's the actuator. The A/C not lighting might be either because it's too cold or the system is inoperative because it's empty of refrigerant (but not sure of that).

I sent back the control unit today for an exchange simply because the ebay seller said everything was testing and working yet the lights did not work. So I'm getting a different used replacement unit mailed from them. As you mentioned @Mooseman, prior to this, changing the control unit will probably do nothing but I figured might as well have a backup. I also ordered brand new ac delco defrost, mode, and driver's side temperature actuators from amazon and they'll be here this Wednesday. If they don't work I can always return them. Love that about Amazon. I did find the passengers side actuator and when I moved the temperature slider the white circle on it didn't move at all so it will probably have to be replaced too. I'm sure the refrigerant will need to be refilled but it should still work. Last time I used the a/c it blew cold air just not that cold.

Fixing this HVAC issue should have taken literally like a day at most but you gotta realize that I know nothing about vehicles and it take time to research and test a possible solution. It's been a great learning experience for me thus far to fix these issues with everyone's input and I really appreciate all your guys help! I wanted to start by testing each part before replacing but it would require me to end up buying a tech 2 clone with a xp laptop which would cost $400 easily vs simply buying 3 actuators off amazon for $130. If those actuator's don't make a difference then oh well I'll just try a different step. The resistor pack for the fan speed 5 only cost $30 and it worked perfectly. I did test the old resistor pack and it didn't click like the new one did when I applied 12v to it with the power probe. So that confirmed the old one was bad. Working smarter not harder means having the right tools to test each part before replacing but since I don't plan on working on thousands of vehicles it's better in my situation to use the part shotgun and take action vs inaction. I take inaction by spending too much time overthinking and not actually trying to replace anything.

So to sum this up, from day 1 here I should have just started applying your feedback replacing parts since there was enough evidence that the most likely culprit were the actuators. Sorry to make such a long post on these forums but now I'm more confident about the solutions to this.
 
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zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
Changed out the 'mode' actuator today. It was a bitch getting the darn actuator out without removing the pedals and floor duct. Reset the hvac fuse. Didn't hear the actuator make any sounds nor did it make any movements. It dawned on me that I could have tested these actuators before buying new ones with my new tool. :bonk: So the last step I took was to apply 12v via power probe to the old actuator and it indeed spun all the gears along with the outer plastic piece. Proof:

Because I've verified that at least one ('mode') actuator works so far but nothing changes in the vehicle I have to assume the actuators are probably not the culprit.
 
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zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
Got up this morning and had some tasty espresso. I was thinking about what else could be causing this hvac system to fail. I went over to rear fuse box and found that the hvac b fuse does not light up whether I'm in accessory mode, engine running, or car completely turned off. Tried another fuse that I verified is working and still nothing...

*UPDATE*

My multimeter wouldn't test voltage at the fuses for some reason... I tested with power probe and was getting 14.1 at HVAC B so power is getting to the fuse when vehicle is running. When vehicle is in accessory mode or off I get no reading nor does a test light come on when checking HVAC B fuse but it lights up on other fuses. Now if that fuse was bad then the voltage reading would be 0.0 when testing while vehicle is running.

In regards to the lights on the hvac unit -- I put my original hvac unit back in and all the lights work. None of the functions work on it though like changing modes. Going to take lunch in a bit and afterwards will update this. Am going to recheck voltages behind the control unit.
 
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budwich

Guru
Jun 16, 2013
1,720
kanata
Perhaps that's why there was no lights on your units ... :smile: hopefully, you can verify and get power to all points that should be there... don't forget to check your grounds.
 

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
I'm so ecstatic!! I finally found the problem to my hvac dilemma. So guess what?? It was the orange wire on the blue connector connecting to the hvac unit. It wasn't actuators, nor the hvac unit itself. When I was testing the fuses in the rear fuse box I had the light probe connected to positive not negative so it wouldn't light up when touching the hvac b fuse. I hooked up my power probe to negative and positive on battery and used the test ground lead for the light probe and then the hvac b fuse would light up. Next, I checked the 125 amp fuse under hood and it was good. So then I checked the orange and 2 brown wires on blue connector to hvac unit. The browns one's read the voltage correct but the orange wire had no power even when the vehicle was in RUN mode. So I applied 12v via my power probe to the orange wire and viola all the controls worked including ac/recirculation, changing fan modes all that! Now the last step is figuring out how to replace that orange wire.
 
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Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,859
Ottawa, ON
Or try to find the break. The most likely place to look would be at the fuse box. Check to see if the contacts in the fuse connectors haven't been spread open by a probe or something. Sometimes a fix is to give the fuse blades a twist.
 

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
Or try to find the break. The most likely place to look would be at the fuse box. Check to see if the contacts in the fuse connectors haven't been spread open by a probe or something. Sometimes a fix is to give the fuse blades a twist.

So to access the fuse blades, the fuse box will need to be disassembled? Is there is a guide for this?
 

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Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,859
Ottawa, ON
I wouldn't take it apart. Jut have a look at the connectors inside where the fuse goes. They shouldn't be spread out, Or check that there is 12V+ on both sides of the fuse at the test points on top.
 

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
Ok there’s 12v at the fuses and underside where 3 orange connectors meet fuse box there is 12v. Behind the connector to hvac head the orange wire is spread. But I think this was caused when I kept popping power probe and t-pin in it.
 

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budwich

Guru
Jun 16, 2013
1,720
kanata
I think you might have little choice but to perhaps run your own wiring from the fuse and splice it just before the hvac controller IF you are saying that the 12v IS leaving the fuse box (if I understand your previous statement).
 
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zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
I think you might have little choice but to perhaps run your own wiring from the fuse and splice it just before the hvac controller IF you are saying that the 12v IS leaving the fuse box (if I understand your previous statement).

You are correct, budwich. I don’t think this is something I can do so I’ll check with local shops and see if they are even willing to run a new line without charging a ‘diagnostic fee’. I’ll find out tomorrow.
 

Reprise

Lifetime VIP Donor
Jul 22, 2015
2,455
You might be able to do this yourself, since you know both ends of the wire.
Go back to the fuse box, verify your power at the fuse, and see if you have continuity for as long as you can reach before the wire disappears.

If you lose continuity somewhere at the back end, cut the wire just before you lose voltage, and splice another of the same gauge. Make sure it's long enough to run to the control head.

If all is well there, go to the front, by the HVAC controller. Do the same thing, working backwards as far as you can.

If you have power at *both* ends of the wire, up to the control head - then I would say the connector is probably jacked up. Replacements are available, but they can be tricky to get the right description. You can take a pic of the connector and match it up online. Also check the GM manual, as they'll name the connector there (I'm too lazy to go look it up for you right now...LOL).

I say it's the connector rather than the head, because you stated that when you ran +12v from the battery, the head worked.

Might save you some time / $$ . Fingers crossed.
 
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budwich

Guru
Jun 16, 2013
1,720
kanata
Oh... I think you can readily do it yourself without much "fanfare". Get one of those "add a circuit" type fuse plugs which plugs into the same location as the existing fuse. You then just run a new "10g" wire thru the firewall towards the place where you want it and splice it onto the orange wire... its probably a $10 fix with little effort and doesn't disturb your fuse box which is a bad idea most times.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,859
Ottawa, ON
Before cutting anything, I'd just try running a test wire to the back of the head and shove the stripped wire into the connector where 12v is supposed to be. As a test, this should confirm the suspicions. If it works, then run the wire permanently. You could even just use the large post at the fuse box since it's always on. Turn the key, connect the test wire and try the HVAC.
 
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zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
You might be able to do this yourself, since you know both ends of the wire.
Go back to the fuse box, verify your power at the fuse, and see if you have continuity for as long as you can reach before the wire disappears.

If you lose continuity somewhere at the back end, cut the wire just before you lose voltage, and splice another of the same gauge. Make sure it's long enough to run to the control head.

If all is well there, go to the front, by the HVAC controller. Do the same thing, working backwards as far as you can.

If you have power at *both* ends of the wire, up to the control head - then I would say the connector is probably jacked up. Replacements are available, but they can be tricky to get the right description. You can take a pic of the connector and match it up online. Also check the GM manual, as they'll name the connector there (I'm too lazy to go look it up for you right now...LOL).

I say it's the connector rather than the head, because you stated that when you ran +12v from the battery, the head worked.

Might save you some time / $$ . Fingers crossed.

If I verified there's no voltage at the HVAC head but there is at fuse box, I would assume there's no continuity when I test from test point at HVAC head to fuse box. There could be a short but I don't have any tools to test if / where the short might be. The rear fuse box goes straight under carpet so I've no idea what path it takes to hit the control head.

Oh... I think you can readily do it yourself without much "fanfare". Get one of those "add a circuit" type fuse plugs which plugs into the same location as the existing fuse. You then just run a new "10g" wire thru the firewall towards the place where you want it and splice it onto the orange wire... its probably a $10 fix with little effort and doesn't disturb your fuse box which is a bad idea most times.

Problem is I don't know where the wiring harness routes from rear fuse box to back of HVAC head. Does it route under sill of doors? Does it route under carpet? Where does it route? The only firewall I'm aware of is the metal divider from engine to interior.

Before cutting anything, I'd just try running a test wire to the back of the head and shove the stripped wire into the connector where 12v is supposed to be. As a test, this should confirm the suspicions. If it works, then run the wire permanently. You could even just use the large post at the fuse box since it's always on. Turn the key, connect the test wire and try the HVAC.

I'll try this during the weekend.
 

budwich

Guru
Jun 16, 2013
1,720
kanata
sorry, I was thinking that the fuse in question was in the engine compartment, hence the "firewall comment". Its even "easier" if you are already inside the vehicle... :smile:
You don't need to know the route of the existing run.... just get a length of what ever size wire is appropriate and run it under the carpet from the rear fuse box to the dash / hvac unit... splice appropriately.
 

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
sorry, I was thinking that the fuse in question was in the engine compartment, hence the "firewall comment". Its even "easier" if you are already inside the vehicle... :smile:
You don't need to know the route of the existing run.... just get a length of what ever size wire is appropriate and run it under the carpet from the rear fuse box to the dash / hvac unit... splice appropriately.

I so want to facepalm right now haha! So basically you're telling me to rip up all the carpet and then go from there? I want to be as non intrusive as possible *( if that's even possible )* Thanks for the help )) Please tell me that I don't have to do anything too crazy. Again, though, if a person has never done such a task, they need a direction of where to route the wire. I have an idea -- post a video of routing a cable of this :smile:
 

budwich

Guru
Jun 16, 2013
1,720
kanata
yikes... the internet is full of ideas on how to run wires under carpet, be it in a house or car. Basically, you can use a "stiff wire" like a clothes hanger and "thread" / pull the wire that you are try to run under the carpet to a "strategic point" and repeat until you got it to the end points that you are interested.. People do it all the time for audio "upgrades", accessory stuff, etc.

anyways, hopefully you get the idea... if not... well, I tried. I think you should just live without AC controls.... :smile:
 
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zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
I was planning on replacing that wire today. Came up with an idea. Before I did anything, I pulled on the orange wire to in connector and retested voltage. It now shows 12v and all functions are working on ac unit. Guess it was a loose wire after all =)
 

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