Hi everyone this is my 1st post here! I have a '99 Bravada I just purchased and have a '00 I've owned for a while. Totally in love with these cars after owning a '99 blazer from new to 235K! Well after changing out a dead battery I noticed that the temp controls were completely dead? No default defroster, no lights nothing? I'm not sure it was working before the battery change either. I checked the 2 fuses for the hvac systems and there blank? No blower motor resistor either, its just blocked off on both of them? I was a mechanic for Lincoln for almost a decade, electrical was my strong suit. I'm totally baffled here, is this system not fused? Before I swap the climate control heads from my other Bravada I thought i would ask the community here because the interior trim on this one i'm having problem with is very brittle (sun damage). I did replace a short vacuum hose on the drivers side firewall with the check valve, the other hoses seem to be ok. Just to clarify this is the computer controlled system with the "auto" feature and the temp sensor in the drivers side headliner (thought it was a cell mic)lol

 

Welcome to the forum!

The automatic temperature control models used a PWM signal to control fan speed rather than the resistor pack.

As far as power to your HVAC controls, fuses 19 (RAD_BATT 15A) & 21 (HVAC 1 10A) located in the instrument panel fuse box provide switched (fuse 21 - hot in RUN) & constant (fuse 19) power to the ECC module. I assume you have checked that both fuses show +12V with the key in the RUN position. If they both show +12V, then I would move to the connector at the back of the ECC and check there for +12V on C6 (brown) and C12 (orange). While you are there, check for proper ground on C10 (black), but at that point, you'd have to have your trim off and you could try swapping the ECC modules between the two trucks.

 

That's great info thank you very much for the pinout. I'm going to get into it this weekend and will post my results. Thank you kindly again!

 

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I apologize for the delay in following up on this thread. Sure enough it was definitely the temp control unit dead. I swapped out another one (oddly an export) from my 2000 Bravada into my 1999 Bravada and everything works fine! I took apart the '99 temp unit to see of anything was weird and no signt of any burnt out surface mount components or bursted caps??? I'm going to re cap it and test some of the resistors and stuff and see if it will come back to life.

 

I apologize for not responding to this thread quicker. I swapped out my temp control unit from my '00 into my '99 Bravada and it totally works, the other one is just dead. I took it apart to see if there were any buldging caps or damage and it looks perfect. I will re cap it and test some of the surface mount components (diodes and restors) and see if i can find a problem.

 

I apologize for not responding to this thread sooner. I did swap in my '00 temp control unit into my '99 Bravada and it worked fine! I took apart the non working one to see if any caps were bursted or anything suspicious looking but all the components look fine.

 

In upper right hand of picture it almost looks as the large square computer block has been hot and burnt a little ....