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H3 HVAC control unit

Old Jan 19, 2020 | 12:52 PM
  #41  
TechnoSean's Avatar
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Originally Posted by hummerz
Read again:

This will happen if the feedback voltage for the air temperature actuators are out
of range.


You need to check the blenddoor actuator, should open close @ command, and make sure there is a clean connection and wiring is proper back to the controller. If you are sure all is good, give it some time to relearn. Btw, can you verify the actuator is properly reset before install.

https://www.youtube.com/watch?v=vWBGKfl7k24
Drumroll. I believe I have it fixed! Here is what I did this morning:
1) Put the 68 ohm 1/2 watt resistor back in line with the 5V lead coming off of the back of the HVAC controller. Recalibrated, and this fixed the temperature issue. This tells me that even this "new" HVAC part number has the voltage problem where it pops slightly out of range. The mode issue persisted.
2) I disconnected all of the actuators and tested the pins on their connector harnesses. I suspected that both pins 2 and 3 should have around 5 volts coming off of them. For all three of the temp/mode actuators pin 3 should be 5V and pin 2 is the position signal. For the right/left temperature actuators I was getting 5v for both pins. For the mode door actuator I was getting 5v coming off of pin 3, but not pin 2. I figured I had a solid place to look at this point.
3) Per my reply last night you can keep the right connector on the HVAC controller and disconnect the left one to test the pins for the actuators. Power comes into the HVAC controller from that right side connector, and the left is just the actuator signals. Pin b is the mode door position signal, pin d is the right temp door position signal, and pin e is the left temp door position signal. All three of those were reading close to 5V. I then cut pin b and tested the voltage at the wire, and it was 5V. Someplace between that point and where it connects to the mode door actuator there must be a short or something. Likely from the radio install I had done 3 years ago, but who knows. Like I said this was working intermittently, but with all the wires behind the new radio I had installed (back-up camera, SiriusXM/etc) maybe this short was just happening sometimes. Regardless, I spliced a new wire from the back of the harness plugged into the left side of the HVAC controller to pin 2 on the mode door actuator's harness. Recalibrated and voila. The recalibration took around a minute like you said it should, and everything works as normal.
4) Cleaned everything up, and did a happy dance.

Thank you Hummerz VERY much for all of the assistance. I will report back in a few weeks once I know this fix keeps working

 
Old Jan 19, 2020 | 01:08 PM
  #42  
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Nice work! Now you know and have good used parts for backup or you could sell them on da'bay.
 
Old Jan 30, 2020 | 09:05 PM
  #43  
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Joined: Jan 2020
Posts: 3
From: North Carolina
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Originally Posted by TechnoSean
Drumroll. I believe I have it fixed! Here is what I did this morning:
1) Put the 68 ohm 1/2 watt resistor back in line with the 5V lead coming off of the back of the HVAC controller. Recalibrated, and this fixed the temperature issue. This tells me that even this "new" HVAC part number has the voltage problem where it pops slightly out of range. The mode issue persisted.
2) I disconnected all of the actuators and tested the pins on their connector harnesses. I suspected that both pins 2 and 3 should have around 5 volts coming off of them. For all three of the temp/mode actuators pin 3 should be 5V and pin 2 is the position signal. For the right/left temperature actuators I was getting 5v for both pins. For the mode door actuator I was getting 5v coming off of pin 3, but not pin 2. I figured I had a solid place to look at this point.
3) Per my reply last night you can keep the right connector on the HVAC controller and disconnect the left one to test the pins for the actuators. Power comes into the HVAC controller from that right side connector, and the left is just the actuator signals. Pin b is the mode door position signal, pin d is the right temp door position signal, and pin e is the left temp door position signal. All three of those were reading close to 5V. I then cut pin b and tested the voltage at the wire, and it was 5V. Someplace between that point and where it connects to the mode door actuator there must be a short or something. Likely from the radio install I had done 3 years ago, but who knows. Like I said this was working intermittently, but with all the wires behind the new radio I had installed (back-up camera, SiriusXM/etc) maybe this short was just happening sometimes. Regardless, I spliced a new wire from the back of the harness plugged into the left side of the HVAC controller to pin 2 on the mode door actuator's harness. Recalibrated and voila. The recalibration took around a minute like you said it should, and everything works as normal.
4) Cleaned everything up, and did a happy dance.

Thank you Hummerz VERY much for all of the assistance. I will report back in a few weeks once I know this fix keeps working

Just joined this forum mainly for this reason, I too will try this same procedure , I have both a Mexico and Portugal module. I am also a Colorado owner and as with clone part issues the OEM battery terminals have been known to cause issues randomly as I experienced with the H3s "step brother".
As for the scarcity of new modules I'm only guessing that GMs parts strike may have somehow affected AC Delco as well as the OEM, I actually called AC Delco and their system said same as retailer " no available date".
 
Old Jan 30, 2020 | 09:18 PM
  #44  
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Joined: Jan 2020
Posts: 3
From: North Carolina
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Originally Posted by Trick1H3T
Just joined this forum mainly for this reason, I too will try this same procedure , I have both a Mexico and Portugal module. I am also a Colorado owner and as with clone part issues the OEM battery terminals have been known to cause issues randomly as I experienced with the H3s "step brother".
As for the scarcity of new modules I'm only guessing that GMs parts strike may have somehow affected AC Delco as well as the OEM, I actually called AC Delco and their system said same as retailer " no available date".
I'll be back on after more diagnosis and attempts, I haven't been too secure about the fact that I just bought my H3T and it has an aftermarket alarm system on it.. most likely spliced in with the BCM. This has all been a headache for me and electrical is not my forte but I'm going to dig in the dash and see if I too have this problem from some sort of auxiliary wiring causing a short.
 
Old Jul 10, 2025 | 03:58 PM
  #45  
Lawson1593's Avatar
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Joined: Jul 2025
Posts: 1
Default Questions about HVAC Issue

Originally Posted by TechnoSean
Drumroll. I believe I have it fixed! Here is what I did this morning:
1) Put the 68 ohm 1/2 watt resistor back in line with the 5V lead coming off of the back of the HVAC controller. Recalibrated, and this fixed the temperature issue. This tells me that even this "new" HVAC part number has the voltage problem where it pops slightly out of range. The mode issue persisted.
2) I disconnected all of the actuators and tested the pins on their connector harnesses. I suspected that both pins 2 and 3 should have around 5 volts coming off of them. For all three of the temp/mode actuators pin 3 should be 5V and pin 2 is the position signal. For the right/left temperature actuators I was getting 5v for both pins. For the mode door actuator I was getting 5v coming off of pin 3, but not pin 2. I figured I had a solid place to look at this point.
3) Per my reply last night you can keep the right connector on the HVAC controller and disconnect the left one to test the pins for the actuators. Power comes into the HVAC controller from that right side connector, and the left is just the actuator signals. Pin b is the mode door position signal, pin d is the right temp door position signal, and pin e is the left temp door position signal. All three of those were reading close to 5V. I then cut pin b and tested the voltage at the wire, and it was 5V. Someplace between that point and where it connects to the mode door actuator there must be a short or something. Likely from the radio install I had done 3 years ago, but who knows. Like I said this was working intermittently, but with all the wires behind the new radio I had installed (back-up camera, SiriusXM/etc) maybe this short was just happening sometimes. Regardless, I spliced a new wire from the back of the harness plugged into the left side of the HVAC controller to pin 2 on the mode door actuator's harness. Recalibrated and voila. The recalibration took around a minute like you said it should, and everything works as normal.
4) Cleaned everything up, and did a happy dance.

Thank you Hummerz VERY much for all of the assistance. I will report back in a few weeks once I know this fix keeps working
Sorry, I know this forum is old, but I’m going to try and do this fix on my 2008 hunmer h3 alpha. The little blue wire you solder the resistor to. Do you know what gauge of wire it is? Want to know in case I want to rewire it in the future or take the resistor out. It probably doesn’t matter but I thought I would ask.

-thanks
 
Old Jul 10, 2025 | 06:52 PM
  #46  
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Originally Posted by Lawson1593
Sorry, I know this forum is old, but I’m going to try and do this fix on my 2008 hunmer h3 alpha. The little blue wire you solder the resistor to. Do you know what gauge of wire it is? Want to know in case I want to rewire it in the future or take the resistor out. It probably doesn’t matter but I thought I would ask.

-thanks

Thicker wires, indicated by lower AWG numbers, have a larger cross-sectional area, which results in lower resistance and higher conductivity. This means they can safely carry more current without overheating or causing damage.



 
Old Jul 11, 2025 | 10:31 AM
  #47  
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Joined: Jul 2007
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Let's cut the necro-bump revitalization of this Old Azzed Thread now please.

It does not make it OK by says "I know this is Old, but" I posted anyways......... just means you realize you should have not dug it up but you think your question is so important why bother doing it correctly.

READ THIS Thread READ: Old Threads/'Necro-Bumping'

You post a NEW Thread and link back to the old one if you think that provides relevant content that is the only way to get your question answered. In this case a new thread simply asking if anyone knows the wire gauge used in the HVAC Controller like referred to in this old thread (insert link).
 
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