sfrasher

This is a 1992 C2500 Silverado diesel with a digital heater controller. Suddenly the digital display went blank and I have no control over the heater. The last thing I had done was changed a battery terminal after the old one fried due to being loose. I know that when I take the terminal off, the heater always resets back to the center position, which is halfway between hot and cold and the fan on low.

I have checked fuses and they all seem okay. Does the heater fuse control the controller? Or does that have a separate fuse somewhere?

Thanks,
Spence

sfrasher

Turned out to be weird! I had replaced the positive battery terminal. So I just removed the negative terminal and put it back on. It all works great now.

Apparently it has something to do with the ECM needing the neg terminal disconnected and reconnected.

Allan In NE

Yes Sir,

That is the control head protecting itself.

That's the procedure when they lock up like that. Just clear it's memory by unhooking the negative cable for a few seconds. Same goes for the ABS and heater/AC control modules.

Allan

stevejohnson48

Hay,since you seem to know what your doing with A/C problems, may be you could help me with this, I have already disconnected the battery serveal times!! and the unit resets itself, but takes on different characteristics !!! I spent about $200.00 dollars on the A/C my 90 K1500 last summer! and when I wanted the heat it started acting up !! check the small survo motors, they seem to do what there suppose to do except when you would try to get the dash vents to stay in one position it would travel right past the dash on to the floor with out stopping, now the only feature I can get is hot air to the windshield ,and the dash control panel arrow indicators blink, both the vertical and the horizontals,so I guess the question I'm asking is the instrument control panel or the servo motors giving me fits??? [[[90 chevy silverado ASM H/AC control panel, the unit I'm looking for has a recycle button were most that I've seen have a MAX air button I need the one that has a the REC button!!!! the way I under stand it the one with the MAX is not enter changeable correct me if I'm wrong]], please advise Steve; is there a way that just run cables to the levels and hot and cold doors and bi pass the electrics

DickO

Hi Folks,
I just now joined this forum and have already profited from it. Many thanks to "sfrasher" and "Allen in NE".

I had replaced both the battery and alternator on my 91 Silverado 3/4 ton just about a month ago. Everything seemed to be just fine up until a few days ago. I found the dome lite still on one nite, reached in and shut it off, and then found the next morning that the truck wouldn't start. Jumped it and drove for awhile and parked it. Then this morning, it wouldn't start again so rejumped and drove for a recharge again.

Except... I found that the electronic heating system didn't want to function at all plus the air conditioner was (luckily) stuck in the 'on' position. No luck using the user's manual of course, so came in and started searching the net. Finally, found this section and decided to give the suggested repair a try (ie, remove and reinstall the battery ground); although, I must admit, I thought it was going to just be a "shot in the dark".

Well, I was badly mistaken. I was so happy to get the panel functioning again. And want to thank you folks for making it happen. Thank you so much. I hope what I've added to your info will reinforce someone else's attempts too.

DickO -- Harveyville, KS

sfrasher

Thanks for the reply. It's nice to know that someone benefits from what we write!

jaygolf

Heres a new twist, Not only has my heater/ac switch gone dark but my power windows and radio now work with the truck turned off. I have installed a new starter and power steering pump recently but everything worked fine after that. I tried the negative battery terminal thing and have checked all the fuses. baffled and bewildered!!!

stevejohnson48

Have you computer decoded by ways of your local parts stores hand held decoder reader ??/ Write the code down save it , Clear the code??/ If there was a hard code it may pop up again and then reference the code to your vehicle it should give you the part and placement on vehicle ??/

joetroubleshooter

Thank you to sfrasher and Allan In NE: I too had a bad positive battery wire, the #8 wire that runs ignition/accessories. I had replaced the + terminal 8 years ago and used a brass clamp type terminal with a screw-in, lead post that installed into the threaded terminal. I silver-soldered the terminal to the cable, including the #8 ignition/accessory wire. It turns out that wire had a splice about 10" from the batt terminal that had eroded to about 3 or 4 strands at the splice. It caused all kinds of havoc. My 4L80E trans kept blowing its 10A fuse and leaving me with just 2nd gear as a default. The wiper controls had been haywire for a couple of years. The same HVAC controls shutoff occurred and after 2 days of troubleshooting and circuit testing, I was still getting nowhere with the HVAC. I checked out this forum and 2 minutes of undoing/reattaching the - terminal and all is well! I use the Sub for towing our 22' 1976 Nomad trailer and am sure glad that I can travel in peace knowing that the phantom electrical problems are over.

TheTooner

'92 C1500 Silverado solved, thanks.