1988 K1500 HVAC controls

[travisc406]

Couple questions. Is the 1988 hvac controls different then every other year. Had a junkyard tell me that and that I would never find the controls. He said best bet is to junk the truck if it’s important to have hvac. Mine only works on ac and defrost. Try changing selection and it does nothing.usually the ac pumps through the defrost vent. And the controls don’t attempt to change to feet. It’s like the buttons is dead. One time after the battery was disconnected for a while when I reconnected battery they worked for a minute. Weird

Also noticed when it’s cold outside and have heat on. There is cold air coming in cab by passengers right foot. Poked my fingers in there and the blend door (I’m assuming) just flops.

 

[DerekTheGreat]

Not true about the controls. 1988 and 1989 are different in appearance. The '88 is black face with black buttons, '89 is silver face with black buttons (My favorite). Everything after is silver face with grey buttons. Starting in 1992 or 1991, a manual recirculation button was added. This is also about the time the blend door motors changed from 8v to 5v or vice versa. That's where the incompatibility happens, the wrong controller might work for twenty seconds or two minutes before the display starts flashing. So if swapping, you just need to make sure you pull a unit from an '88 to '90 truck. Swap your face and buttons as needed.

I think that's the recirc blend door motor. From what I've read, that's a fairly common problem. When the HVAC system is turned off, the system tries to close the door, but that motor doesn't provide any feedback and so after awhile the plastic teeth strip out.

 

[DeCaff2007]

This is why I have the manual controls. Sliders instead of buttons. Much easier to operate and repair when needed.

As for the change from 8V to 5V or vice versa, never heard of that. Why would GM do such a thing?

 

[travisc406]

Not true about the controls. 1988 and 1989 are different in appearance. The '88 is black face with black buttons, '89 is silver face with black buttons (My favorite). Everything after is silver face with grey buttons. Starting in 1992 or 1991, a manual recirculation button was added. This is also about the time the blend door motors changed from 8v to 5v or vice versa. That's where the incompatibility happens, the wrong controller might work for twenty seconds or two minutes before the display starts flashing. So if swapping, you just need to make sure you pull a unit from an '88 to '90 truck. Swap your face and buttons as needed.

I think that's the recirc blend door motor. From what I've read, that's a fairly common problem. When the HVAC system is turned off, the system tries to close the door, but that motor doesn't provide any feedback and so after awhile the plastic teeth strip out.

That makes sense I did swap a newer one out a while ago that I thought had something wrong with the module. It did that very thing started working then flashed and quit. Just figured it was a bad unit.

 

[someotherguy]

This is why I have the manual controls. Sliders instead of buttons. Much easier to operate and repair when needed.

As for the change from 8V to 5V or vice versa, never heard of that. Why would GM do such a thing?

Sliders? Heat only, non-A/C truck I'm guessing? Got a pic of your controls please sir?

Richard

 

[someotherguy]

Not true about the controls. 1988 and 1989 are different in appearance. The '88 is black face with black buttons, '89 is silver face with black buttons (My favorite). Everything after is silver face with grey buttons. Starting in 1992 or 1991, a manual recirculation button was added. This is also about the time the blend door motors changed from 8v to 5v or vice versa. That's where the incompatibility happens, the wrong controller might work for twenty seconds or two minutes before the display starts flashing. So if swapping, you just need to make sure you pull a unit from an '88 to '90 truck. Swap your face and buttons as needed.

I think that's the recirc blend door motor. From what I've read, that's a fairly common problem. When the HVAC system is turned off, the system tries to close the door, but that motor doesn't provide any feedback and so after awhile the plastic teeth strip out.

Sounds like two possible issues:

1. Linkage sliders gummed up on the vent position actuator assembly, just above the driver's side of the transmission hump. Clean 'em gently and re-lube with a little white lithium.

2. Recirculate actuator bad, this is the one up above the blower motor housing. A little tight to swap out but not overly difficult unless you got huge ham fists.

Both of these are very common issues at this age of the trucks.

Agreed on the generations of controllers. Junkyard dude is nuts for telling you to get rid of the truck if having A/C is important. He's either totally misguided, or attempting to misguide you in hopes your truck will end up in his yard for cheap..

Richard

 

[DeCaff2007]

Sliders? Heat only, non-A/C truck I'm guessing? Got a pic of your controls please sir?

Richard

Yes, and the heat works quite well FWIW. Sorry, no pics at the moment. As nice as A/C is to have, it's only needed for a few days out of the year in NEPA. All other times, you need heat or no climate control at all. Also, A/C makes it a lot more difficult to work around things in the engine bay.

Also, the slider controls are not compatible with the electronically controlled actuators. Lots of modification required there. Funny part is, I've yet to see an 88/89 model year in the junkyard with slider controls.

Lastly, for the record, my Bonneville and the Ford Fusion I used to have, both had overly complicated electronic controls for the HVAC. Both have A/C, both have auto climate control displays. Not a fan of either one. Oh and my 05 Silverado had manually controlled temperature, but with rheostats that cleverly looked like sliders. Intuitive but problematic.

 

[someotherguy]

Yes, and the heat works quite well FWIW. Sorry, no pics at the moment. As nice as A/C is to have, it's only needed for a few days out of the year in NEPA. All other times, you need heat or no climate control at all. Also, A/C makes it a lot more difficult to work around things in the engine bay.

Also, the slider controls are not compatible with the electronically controlled actuators. Lots of modification required there. Funny part is, I've yet to see an 88/89 model year in the junkyard with slider controls.

Lastly, for the record, my Bonneville and the Ford Fusion I used to have, both had overly complicated electronic controls for the HVAC. Both have A/C, both have auto climate control displays. Not a fan of either one. Oh and my 05 Silverado had manually controlled temperature, but with rheostats that cleverly looked like sliders. Intuitive but problematic.

Right, that was my point - slider controls are for the heat-only trucks. All the GMT400's with A/C are electronic controls of either variety - the pushbutton 88-94 or dial 95-up. No sliders/cables, no vacuum components (other than that one heater hose control valve on some of the later model stuff.)

Richard

 

[DeCaff2007]

Ok fair enough. I would like to point out, however, that the HVAC controls on my 83 Grand Prix are all sliders. Guess what it came equipped with from the factory: Air Conditioning. So was OCEACC (Overly Complicated Electronic Air Conditioning Controls) a 90's thing, or just a GMT400 thing?

 

[someotherguy]

Ok fair enough. I would like to point out, however, that the HVAC controls on my 83 Grand Prix are all sliders. Guess what it came equipped with from the factory: Air Conditioning. So was OCEACC (Overly Complicated Electronic Air Conditioning Controls) a 90's thing, or just a GMT400 thing?

We're talking GMT400's here. I'm fully aware a very large number of other vehicles have slider controls with A/C.. I am old, you know.. lol

BTW you think a 400 has overly complicated A/C controls, wait til you have to troubleshoot/repair a GMT800's dual zone/automatic controls. I'm glad that so far the only thing wrong with mine is the recirc door is broken.

Richard