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Need help please 1988 chevyc1500 ac/heater unit

Discussion in 'GM Electrical Tech' started by Moilan57, May 21, 2013.

  1. Moilan57

    Moilan57 New Member

    My ac/heater unit is not displaying anything. Everything else on the dash works. I just bought the truck. There is a aftermarket radio in it. Im thinking when they put that in they did something wrong. Anyone know what i should look for.
  2. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    What do you mean by not displaying anything? Can you describe it more detailed to help others understand better?

    Also Welcome to the site I hope some one can help you out :glasses:
  3. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Step 1 would be to check all the fuses, even if they dont appear to be related to the system in question, Ive found in the past systems that you would assume to be not related have input or signal wires that allow power up.

    Step 2 would be to open the dash and check for loose plugs, cut wire, or even tape or connectors where a wire might have been repaired. Sometimes novice stereo installers can get a little messy.

    Step 3 would be to use a multi meter to check the system plugs for proper power inputs/outputs.
  4. Moilan57

    Moilan57 New Member

    Sorry i didnt know i had any replies. I thought i was suppose to get a email. Anywayz the whole control unit does not work. It doesnt have any power. I unplugged it and got a test light and tested the plug. There are 5 wires on the plug and all except the middle wire are showing power. The wire is green. I cant find a wiring diagram for this truck. If you know anything else i would appreciate it. Thank you
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Moilan57 try a Google search using "1988 Chevrolet truck wiring" I found a mess of good wiring diagrams for your truck, unfortunately Im using a Kindle for access so its hard to expend the diagrams and read them.
  6. csltrains96

    csltrains96 Rockstar 100 Posts

    If you can't find anything wrong with the wiring, the display driver for the unit, or the logic board may have gone bad. The displays for these trucks were pre LCD/LED and are actualy plasma discharge displays. The driver circuit that excites the display may have given up the ghost. In that case, it's time for a new unit.

    My '89 also has the digital display for the AC/heating/cooling controls. I've noticed that LMC truck sells a replacement, but it is still a spendy little unit.
  7. Moilan57

    Moilan57 New Member

    Yes i was thinking that also do you know if a good place i can get that ac unit
  8. csltrains96

    csltrains96 Rockstar 100 Posts

    I've only seen it in the LMC catalog. I suppose that a U-Pull it yard might have one or two, but you never know if that will work for you until you try to install it.

    AC controls.jpg

    LMC wants $599 for the unit. Maybe the wrecking yard will be cheaper.
  9. Moilan57

    Moilan57 New Member

    Alright i found another problem i took the ac/heater control unit apart. It is the digital one, the third one on the post. Inside the display screen has a burn mark. Do you know what could have blown to cause that. Thank you for your help
  10. csltrains96

    csltrains96 Rockstar 100 Posts

    I've never had mine out of the truck, let alone opened up. Maybe someone else will have some experience with repairing one of these.

    Good luck.

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