AC / Heater stuck in hot temp control and high fan

[Plumber101010]

CRAP!!!  One guy just told me to make sure I don’t touch any of the controls for two minutes....now he tells me... lmao!  

 

It was dead and nothing happened but everything else came on but I did try to adjust the fan and turn the AC on after about 30 seconds but still nothing. Dang it!!! Any chance this could be a fuse related issue even though fan and temp control out working in the last position i used???

 

 

[diyer2]

21 hours ago, Plumber101010 said:

They are brand new, both a month old. But completely drained them to dead 1/2 dozen times now. Long story as to why but know why. So what are we trying to achieve by waiting 24 hours just so I know?  Is that how long it takes to reset the computer  because voltage is stored up somewhere?

24 hours will generally achieve full charge, 12.5 volts minimum.

So the new batteries go dead when the truck isn't running?

[Doug_Scott]

1 hour ago, Plumber101010 said:

CRAP!!!  One guy just told me to make sure I don’t touch any of the controls for two minutes....now he tells me... lmao!  

 

It was dead and nothing happened but everything else came on but I did try to adjust the fan and turn the AC on after about 30 seconds but still nothing. Dang it!!! Any chance this could be a fuse related issue even though fan and temp control out working in the last position i used???

 

 

Are you saying you only have the high speed fan?  It's a long standing issue that I thought GM had addressed years ago. I have a feeling that maybe we should have asked this back on message 2 or3. 

 

Do you have all of the fan speeds? Check all the fuses again using a test light. Connect clip on ground/negative post of battery and using the probe, touch both sides of the fuse on the top of the fuse. Fuses can look ok yet will fail thr test with the probe.

 

If you are having both batteries going dead there must be a reason. Take the ground cables off of both batteries and take your test light and connect one end to the disconnected cable and the other end to the battery.  It should not light up.  If it does light up you have something wrong. 

[Plumber101010]

3 hours ago, diyer2 said:

24 hours will generally achieve full charge, 12.5 volts minimum.

So the new batteries go dead when the truck isn't running?

 I think you’re misunderstanding I’m not charging the batteries go back and read I was supposed to disconnect the batteries and wait 24 hours to reset the computer

[Plumber101010]

None of the buttons knobs or controls are operative. None of the lights light up. For all practical purposes the unit is completely dead as if we pulled the fuse. But it is working in the last position that I had it on before it went dead so the fan is stuck in the medium blow position and the temperature control is stuck in the hot but it works, but you can’t control anything 

[Plumber101010]

 I don’t want anyone to focus on why the batteries are going dead that’s why I haven’t touched upon it. I know what the reason for that is but that will open up a whole other subject and another door for conversation. For all practical purposes this is a totally different issue and I know why the batteries are going dead and that something that’s unrelated to this problem.

 

It’s just that in the process of jumping the truck with the 450 amp power pack which I should not be doing but using a slow charge, the computers always go haywire because it rapidly blinks on and off a dozen times  a second before it starts lol.

 

And this time was the worst ever  with the electronics coming on and off rapidly as it was trying to start because it was dragging and when it finally started is when the AC heater got stuck in its last used position 

[Plumber101010]

2 hours ago, Doug_Scott said:

Are you saying you only have the high speed fan?  It's a long standing issue that I thought GM had addressed years ago. I have a feeling that maybe we should have asked this back on message 2 or3. 

 

Do you have all of the fan speeds? Check all the fuses again using a test light. Connect clip on ground/negative post of battery and using the probe, touch both sides of the fuse on the top of the fuse. Fuses can look ok yet will fail thr test with the probe.

 

If you are having both batteries going dead there must be a reason. Take the ground cables off of both batteries and take your test light and connect one end to the disconnected cable and the other end to the battery.  It should not light up.  If it does light up you have something wrong. 

 

[Plumber101010]

I have not checked the fuses yet only because as I said,  I assumed that since the fan is blowing even though it’s stuck in that position that it would not be a fuse issue. Am I wrong in thinking that? I asked that earlier if it’s possible that it could still be a fuse issue since the fan is blowing?

 

Is there more than one fuse for this and are they all under the hood or on the side panel by the drivers door? 

[Jsdirt]

ALRIGHT ... so you've got a big charger capable of mega-amperage. Any chance the voltage rose above 15v for any length of time? Was it monitored with a volt meter, or did you just let the modern charger do it's thing?

 

If it got higher than 15 volts, I'd wager some computers went up in smoke ... and that would explain alot ...

[Plumber101010]

48 minutes ago, Jsdirt said:

ALRIGHT ... so you've got a big charger capable of mega-amperage. Any chance the voltage rose above 15v for any length of time? Was it monitored with a volt meter, or did you just let the modern charger do it's thing?

 

If it got higher than 15 volts, I'd wager some computers went up in smoke ... and that would explain alot ...

It wasn’t a charger it’s a portable jumper battery pack 450 amp 

[Plumber101010]

I’m guessing That’s it? If disconnecting  the batteries doesn’t work it’s something more serious??  Like I  fried a computer board?  It was getting too hot so I pulled the fuse on The driver side inside panel that controlled  the fan but still the outside air makes it unbearably hot 

[Jsdirt]

Ahh, gotcha.

 

I guess the repeated charge/discharge cycles fried the HVAC module - that's my best guess from  here. They way they build things today, this wouldn't shock me one bit.

[Doug_Scott]

4 hours ago, Plumber101010 said:

I have not checked the fuses yet only because as I said,  I assumed that since the fan is blowing even though it’s stuck in that position that it would not be a fuse issue. Am I wrong in thinking that? I asked that earlier if it’s possible that it could still be a fuse issue since the fan is blowing?

 

Is there more than one fuse for this and are they all under the hood or on the side panel by the drivers door? 

GM has had issues for decades with the way they control fan speeds.  There is a module MoU Ted to the HVAC under the dash.  They will melt and short out the lower fan speeds.  High speed used to have an inline fuse for high speed only at one timr, they likely still have a fuse for the high speed, and a fuse for the rest. If you do a search here for fan module or blower module you should find it. 

Do you know why the batteries are going dead? Use the KISS way to diagnose before thinking it's something in a computerized object. 

[Doug_Scott]

5 hours ago, Plumber101010 said:

 I don’t want anyone to focus on why the batteries are going dead that’s why I haven’t touched upon it. I know what the reason for that is but that will open up a whole other subject and another door for conversation. For all practical purposes this is a totally different issue and I know why the batteries are going dead and that something that’s unrelated to this problem.

 

It’s just that in the process of jumping the truck with the 450 amp power pack which I should not be doing but using a slow charge, the computers always go haywire because it rapidly blinks on and off a dozen times  a second before it starts lol.

 

And this time was the worst ever  with the electronics coming on and off rapidly as it was trying to start because it was dragging and when it finally started is when the AC heater got stuck in its last used position 

Sorry, I read my emails in the wrong order.  Something you need to understand, computer stuff in cars/trucks are protected quite well. They also usually operate at voltages around 5 volts.  All the sensors are 5 volts. That's why the connectors have to so clean they are pristine. 

If I am reading this correctly you have not checked the fuses yet?  Please take the 5 minutes to check the fuses.

[Plumber101010]

2 hours ago, Doug_Scott said:

Sorry, I read my emails in the wrong order.  Something you need to understand, computer stuff in cars/trucks are protected quite well. They also usually operate at voltages around 5 volts.  All the sensors are 5 volts. That's why the connectors have to so clean they are pristine. 

If I am reading this correctly you have not checked the fuses yet?  Please take the 5 minutes to check the fuses.

I only found 3 fuses. For some ridiculous reason the owners manual no longer shows a fuse box... so I had to wing it and just check them all.

 

Under the hood there is a 4 pin, square looking larger fuse and I pulled and put back in place and it did absolutely nothing. 

 

On the driver side dash panel, I found two small blade fuses marked for something related I forget and first one was a good fuse and nothing happened when I took it or nothing changed.

 

Second one was also good and when I took it out the fan stop blowing and shut off the fan blower.