# 2017 hvac controls non functional



## 71mk3lincoln (Feb 6, 2021)

2017 cruze lt all fuses good. No lights on control panel under dash. No response when buttons pressed. Replaced the control panel with dealer part. Still not working. Is there a hvac bcm? Which number on the fuse panel would that be? Took it to dealer also. They reccomended replacing the control unit but did not know if that was the real fix. Any suggestions? I presently have battery disconnected hoping a reset will reactivate the new control panel. 

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## Ma v e n (Oct 8, 2018)

Fuse 21 (10amp) in the center console is the fuse for the HVAC control module, which is separate from the HVAC switchgear.


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## snowwy66 (Nov 5, 2017)

And yes. The hvac goes through the bcm.


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## 71mk3lincoln (Feb 6, 2021)

snowwy66 said:


> And yes. The hvac goes through the bcm.


Do you know the location of this bcm? I may need to start probing wires. 

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## Ma v e n (Oct 8, 2018)

The BCM is the body control module. The HVAC is controlled by HVAC control module. The BCM is involved, but it doesn't communicate directly with the HVAC switchgear. 
Without you knowing the difference between the BCM, the HVAC controls, and the HVAC control module I'm not sure "probing wires" is your best first diagnostic step. 

Finding someone with access to a full vehicle level scan tool would be preferable to randomly probing wires. You probably have a bad power or grind circuit to the HVAC control module, a bad module or a failed LIN network wire. Additionally you could have an open power ground or comms wire to the switches. A DTC scan would give you a great starting point instead of randomly guessing at what module to replace or what wires to "probe"


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## 71mk3lincoln (Feb 6, 2021)

Ma v e n said:


> The BCM is the body control module. The HVAC is controlled by HVAC control module. The BCM is involved, but it doesn't communicate directly with the HVAC switchgear.
> Without you knowing the difference between the BCM, the HVAC controls, and the HVAC control module I'm not sure "probing wires" is your best first diagnostic step.
> 
> Finding someone with access to a full vehicle level scan tool would be preferable to randomly probing wires. You probably have a bad power or grind circuit to the HVAC control module, a bad module or a failed LIN network wire. Additionally you could have an open power ground or comms wire to the switches. A DTC scan would give you a great starting point instead of randomly guessing at what module to replace or what wires to "probe"


Without the animosity your attempting to convey you would see its already been to the dealer. They spent 4 hours with the scan tools and all they could tell me was the it MAY be the control panel. But they dont know. I did not know i needed to type out my whole intention when asking which body control module the hvac control unit was assoiated with because my googling has informed me of 8 of the. But i planned to probe power wire to make sure its getting full power and not just referance voltge. Then go on to checking for grounds and looking for damaged wires.... but glad i could make you feel superior to me because i asked a question. Tou internet mechanics are all the same. Gotta jerk around and blow your load just for your own condicending pleasure. 

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## Ma v e n (Oct 8, 2018)

71mk3lincoln said:


> Without the animosity your attempting to convey you would see its already been to the dealer. They spent 4 hours with the scan tools and all they could tell me was the it MAY be the control panel. But they dont know. I did not know i needed to type out my whole intention when asking which body control module the hvac control unit was assoiated with because my googling has informed me of 8 of the. But i planned to probe power wire to make sure its getting full power and not just referance voltge. Then go on to checking for grounds and looking for damaged wires.... but glad i could make you feel superior to me because i asked a question. Tou internet mechanics are all the same. Gotta jerk around and blow your load just for your own condicending pleasure.
> 
> Sent from my SM-G950U using Tapatalk


There's was ZERO animus in my previous posts. I mentioned you should access a scan tool because it's pretty clear that whatever diagnostics were done weren't complete.
I dont come here to help people because it makes me feel superior. Because honestly, even if it did have that affect, every post I make on this forum that provides others with technical details, diagnostic information or schematics has the potential to cost me real money in my daily livelihood.
So maybe you get off your high f#cking horse, realize there are people who offer help for no reasons other than enjoying helping or interacting with people, especially during a time when in person interaction is in short supply. Acknowledge that the written word, especially on a forum is often fraught with dangers of misunderstood tone, and be thankful. Enjoy your f#cking schematics @sshole.


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## 406 (Apr 5, 2019)

Mic. Drop. Lol


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## 71mk3lincoln (Feb 6, 2021)

Ma v e n said:


> There's was ZERO animus in my previous posts. I mentioned you should access a scan tool because it's pretty clear that whatever diagnostics were done weren't complete.
> I dont come here to help people because it makes me feel superior. Because honestly, even if it did have that affect, every post I make on this forum that provides others with technical details, diagnostic information or schematics has the potential to cost me real money in my daily livelihood.
> So maybe you get off your high f#cking horse, realize there are people who offer help for no reasons other than enjoying helping or interacting with people, especially during a time when in person interaction is in short supply. Acknowledge that the written word, especially on a forum is often fraught with dangers of misunderstood tone, and be thankful. Enjoy your f#cking schematics @sshole.
> 
> ...


Ok. I apologize. We got off on the wrong foot. It just sounded like you were talkin down assuming i dont know what im doing..... my bad. But i tested around and know the bcm is communicating with the hvac control mod. Got power from that mod to the switch panel on the dash. But nothing from there. In the schematic you posted it seems to me that the hvac module is fed by the collision detection system. I cant post pics till i get premium membership. Lol. But i think its the 3rd pic you posted.... am i reading this correctly? The car was wrecked and insurance denyed the owner. She can not afford shop prices on putting it back together. The airbag system did not deploy. But the sensors on the front end were damaged. So from the diagram i am assuming the fact that the sensors are not hooked up may he keeping the hvac from working? I am not a mechanic. Just a tinkerer who knows just enough to get me deep in ****. 

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## Maqcro1 (Apr 29, 2019)

71mk3lincoln said:


> Ok. I apologize. We got off on the wrong foot. It just sounded like you were talkin down assuming i dont know what im doing..... my bad. But i tested around and know the bcm is communicating with the hvac control mod. Got power from that mod to the switch panel on the dash. But nothing from there. In the schematic you posted it seems to me that the hvac module is fed by the collision detection system. I cant post pics till i get premium membership. Lol. But i think its the 3rd pic you posted.... am i reading this correctly? The car was wrecked and insurance denyed the owner. She can not afford shop prices on putting it back together. The airbag system did not deploy. But the sensors on the front end were damaged. So from the diagram i am assuming the fact that the sensors are not hooked up may he keeping the hvac from working? I am not a mechanic. Just a tinkerer who knows just enough to get me deep in ****.
> 
> Sent from my SM-G950U using Tapatalk


just an idea... you say the control panel has no response? Does that mean no power or that nothing is moving? I know this is gen 2 but the gen 1 had issues with HVAC actuator gears breaking.


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## 71mk3lincoln (Feb 6, 2021)

Maqcro1 said:


> just an idea... you say the control panel has no response? Does that mean no power or that nothing is moving? I know this is gen 2 but the gen 1 had issues with HVAC actuator gears breaking.


No lights on the control panel. No feed back. Nothing working at all. Got power to the new panel but no outgoing signal to say..... the blower motor. Or blend door actuator. I replaced the control panel with a brand new gm part from the dealer. Cost 176 i think. 

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## Maqcro1 (Apr 29, 2019)

71mk3lincoln said:


> No lights on the control panel. No feed back. Nothing working at all. Got power to the new panel but no outgoing signal to say..... the blower motor. Or blend door actuator. I replaced the control panel with a brand new gm part from the dealer. Cost 176 i think.
> 
> Sent from my SM-G950U using Tapatalk


Got it. Definitely some sort of power issue or communications error.


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## 71mk3lincoln (Feb 6, 2021)

Maqcro1 said:


> Got it. Definitely some sort of power or communications error.


Yup. Im think i found a work around ima try tomorrow. Pull the sdm and jump the 2 green wires on the harness with a fused link and see if the system functions. From the info ive acquired the sdm is a pass through mod that has to do with the collision detection system... this car was wrecked so im wondering if its tripped somthing in the sdm that the dealer overlooked.... idk. The cars just out of warranty and we cant afford their prices. 

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## Maqcro1 (Apr 29, 2019)

71mk3lincoln said:


> Yup. Im think i found a work around ima try tomorrow. Pull the sdm and jump the 2 green wires on the harness with a fused link and see if the system functions. From the info ive acquired the sdm is a pass through mod that has to do with the collision detection system... this car was wrecked so im wondering if its tripped somthing in the sdm that the dealer overlooked.... idk. The cars just out of warranty and we cant afford their prices.
> 
> Sent from my SM-G950U using Tapatalk


accidents can cause a headache of issues. Even after replacing seat belts, airbags, impact sensors and whatever else is damaged, you still have the after effects on the computers. I know other manufacturers like Honda will store the crash data permanently onto the ECM/BCM and the airbag light will be on forever.

Not sure why that would affect the HVAC controls.


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## 71mk3lincoln (Feb 6, 2021)

Maqcro1 said:


> accidents can cause a headache of issues. Even after replacing seat belts, airbags, impact sensors and whatever else is damaged, you still have the after effects on the computers. I know other manufacturers like Honda will store the crash data permanently onto the ECM/BCM and the airbag light will be on forever.
> 
> Not sure why that would affect the HVAC controls.


The airbags were not triggered. Everything else works in the car ecept hvac. And what has me chasing this idea is in the first pic the guy posted for me up above. The far right of the pic you see where it says hvac is tied to the inflatable restraint diognostic system. It goes from that. To the serial data link. To the hvac control mod to the control panel. That would explain why i got power to the control panel but since its not getting signal from the serial data port its not functioning.... im horrible with electrical. I am learning new stuff as im talking to you lol. Makes me love my 71 lincoln soooooo much more. 

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## Snipesy (Dec 7, 2015)

71mk3lincoln said:


> The airbags were not triggered. Everything else works in the car ecept hvac. And what has me chasing this idea is in the first pic the guy posted for me up above. The far right of the pic you see where it says hvac is tied to the inflatable restraint diognostic system. It goes from that. To the serial data link. To the hvac control mod to the control panel. That would explain why i got power to the control panel but since its not getting signal from the serial data port its not functioning.... im horrible with electrical. I am learning new stuff as im talking to you lol. Makes me love my 71 lincoln soooooo much more.
> 
> Sent from my SM-G950U using Tapatalk


The IRSDM is just a daisy chain setup. They are hooked together internally.

This makes wire harness setups easier. No splicing. That’s all it is.


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## 71mk3lincoln (Feb 6, 2021)

Snipesy said:


> The IRSDM is just a daisy chain setup. They are hooked together internally.
> 
> This makes wire harness setups easier. No splicing. That’s all it is.


What does this mean with the issue im facing. Am i barking up the wrong tree here? 

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## Snipesy (Dec 7, 2015)

71mk3lincoln said:


> What does this mean with the issue im facing. Am i barking up the wrong tree here?
> 
> Sent from my SM-G950U using Tapatalk


Most likely wrong tree, yes. If it was a problem with serial communications the dealership probably would of seen it. Which really confuses me because everything points to this being the problem. And fixing that is almost always a new HVAC Control Module.

Wiring problems are possible. But unlikely unless someone really went in there and did a number.

The easiest test is pulling BCM codes. The BCM doesn’t really control HVAC, but it’s responsible for relaying the HVAC ac compressor requests to the ECM. If the HVAC module is not doing this you will get something along the lines of “LOST COMMUNICATION WITH HVAC CONTROL MODULE”.


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## 71mk3lincoln (Feb 6, 2021)

Snipesy said:


> Most likely wrong tree, yes. If it was a problem with serial communications the dealership probably would of seen it. Which really confuses me because everything points to this being the problem. And fixing that is almost always a new HVAC Control Module.
> 
> Wiring problems are possible. But unlikely unless someone really went in there and did a number.
> 
> The easiest test is pulling BCM codes. The BCM doesn’t really control HVAC, but it’s responsible for relaying the HVAC ac compressor requests to the ECM. If the HVAC module is not doing this you will get something along the lines of “LOST COMMUNICATION WITH HVAC CONTROL MODULE”.


Ok well let me throw ya a curve ball i forgot to mention because i thought i fixed it. But may be the issue staring me in the face..... at one point this car had a aftermarket head unit in it. And the previous owner took it out and put the factory one back in. But once i got the car road worthy i took it for a test drive and the radio stopped working on a bump. Upon investigation i found 2 wires rubbing on metal. The wires were primary green b7t forgot the stripe colors. I taped em up. Not thinking much. Radio works. Yay..... but even with the new control panal no heater functions..... but. Maybe these 2 green wires are comunication wires to display the control panel functions on the radio...... they just did not hook em up? The wires were flush cut when i found em. Like fresh cut harness.. both went into the radio harness too. If i remember right. 

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## 71mk3lincoln (Feb 6, 2021)

And see it has c9mmunication through the whole system from bcm to the hvac control mod then to the control board itself. Just nothing from there to the ancelery units like actuators and blower motors. Thats why its not throwing codes. 

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## Snipesy (Dec 7, 2015)

71mk3lincoln said:


> And see it has c9mmunication through the whole system from bcm to the hvac control mod then to the control board itself. Just nothing from there to the ancelery units like actuators and blower motors. Thats why its not throwing codes.
> 
> Sent from my SM-G950U using Tapatalk


Ah I see.

We’re missing the wiring schematics for those radio wires.

They are a part of the “Gateway isolated low speed GMLAN bus”. And they come from that serial data gateway we see in the diagrams.

You can blame GM for making things complicated. But all the radio and Onstar stuff are separated by that gateway. That is it’s purpose.

I do not believe this bus is required for vehicle operation. But I could be very wrong. GM designs things weird.


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## 71mk3lincoln (Feb 6, 2021)

You know. I tried the onstar button and it did not work either now that i think about it. So this buss your talkin about. How do i go forward from here

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## Snipesy (Dec 7, 2015)

71mk3lincoln said:


> You know. I tried the onstar button and it did not work either now that i think about it. So this buss your talkin about. How do i go forward from here
> 
> Sent from my SM-G950U using Tapatalk


We need the serial schematics of those gateway isolated buses.


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## 71mk3lincoln (Feb 6, 2021)

Ok well hopefully someone will chime in with what we need. 

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