Phantom Electrical Problem

A couple of years ago, my wife started haveing a problem wih her 93 S10 4.3L Automatic.
On a summer day with a high temperature, she could drive the truck for a while, stop at a store, and when she would come back to drive away, the following symptoms would happen. The dash brake light would stay on, the heating and air would not function, and the transmission would not up shift from low. Sitting there for 15 or 20 minutes, restarting, and trying again would make the problem go away. Problem was that it was hit and miss as to when it would happen. We carried it to a repair shop. They could not duplicate the problem. We even took it to a transmission shop where they reported there was nothing wrong with the transmission.

So, we've simply lived with the problem for a long time, until now... A few weeks ago, she came back to the house and told me that the temp guage was no longer working on the truck. So, this last weekend, I looked into it. I replaced the coolent temperature sensor, thinking there was nothing wrong with the old one anyway. And, sure enough it wasn't the problem. So, into the dash I went. After standing on my head for about an hour, I removed the instrument cluster. Didn't find any visible problems with the units curcuit, except a couple of cluster lights that were burned out. I replaced them.

Okay, I'll try to close this before it gets too long winded... I carefully put everything back together. And, the outcome is this... The phantom problem that we have had for years is now constent... I did a manual scan by shorting terminal A and B on the computer plug, as I read about. And the code is a constant 12. Which is normal.

So, now we have a truck that won't shift, has no air or heat, and a constant dash brake light. Seems last night she metioned that when it happens the radio quits too. I didn't check that. Ive done lots of searching, hoping to find some clue. But have so far come up empty handed....

Does anyone out there have a suggestion...????
Thank you for taking the time to read this book...
BW@

I have no answers but I would suggest you tackle one problem at a time. You may fix all of the problem with one reapair. Also insure all electrical grounds a making good contact. I would start with the brake light. Then if the heat and air still do not work that would be next. Safety than comfort.

hi,try unplugging your computer for about 15 min.,then hook it back up .if this doesnt work ,try unhooking the ground wire on the battery for the same amount of time .if this fails u probably need a new computer .hope this helps,jimmy

Hard to do, but all the major ground connections are on the back of the engine, upper part of head on each side. These sure do get corroded and will create havoc when they do. Try loosening the bolt, wiggle the connectors, and retighten, each side.

hi,try unplugging your computer for about 15 min.,then hook it back up .if this doesnt work ,try unhooking the ground wire on the battery for the same amount of time .if this fails u probably need a new computer .hope this helps,jimmy

Just unplug the negative battery cable, does the same thing.

Being under a "time crunch", I've bit the bullet and taken it to a repair shop. I've used these guys for years, and, trust them. So, if they solve the problem, I'll at least reply here and let you know what the problem was...
Thank you for your responses.
BW@

Keep us posted.

I really want to know what the problem was.

After all this time...

Seems that my digging around under the dash while removing and re-installing the instrument cluster, made the connection just bad enough for the problem to be constent, as I suspected. And, thankfully, without too much effort the guys down at the local auto repair shop that I have done business with for years found and fixed the problem...

Believe it or not, the ignition connector under the dash was not properly snapped into place (closed). And, that was causing the problem all along. I guess I must have made the connection a little worse with my moving things around. Until finally the unstable connection finally became a bad connection...

Anyway, she is a happy camper now.... Even had them do some needed maintenance that I'd put off, not knowing what we were going to do with the truck....

Just another reality check on me, to leave some things to the experts...
But, I did tell my wife that I should at least get credit for breaking it well enough for it to finally get fixed..... !!!!

Thank you all for your feedback. And, good luck on your quests...
Now it's off the the '65 chevy stepside that I'm restoring... At least, I know what all the parts are in there....!!!

BW@

Let us help you further for a second.

What maintenance did you have done?

Oh, nothing more than being lazy/busy.... Had them give it a tune-up, oil change, check the brakes, re-charge the ac, and flush the cooling system...
Like I said, I'd been putting off that stuff, not knowing if we could even get it back on the road... Now, I'll keep up with servicing it...

By the way, we suspect that the ignition connection got knocked partially loose when one of our son-in-laws said he could save us money and replace a leaky heater coil a couple of years ago... Truth is, as a mechanic, he makes a pretty good deputy sheriff....!! But, who am I to talk....

Enjoy your day,
BW@

What did the tuneup contain exactly?