Hello guys, I have been using your forums for quite sometime and have managed to find answers to many of my questions on here and I even rebuilt my transmission and adjusted it using this forum. I love this place...Hands down! I just recently experienced my A/C and Tachometer failing on me, and the wait to start light stays only once you start the truck. I replaced the battery in it and these problems arose, the pcm was replaced about 3 months ago because I found a low positive voltage coming out of the ground wire. Replaced the PCM and she ran and shifted just fine, found out the old PCM was not letting her get into O.D. So with that out of the way...what in the heck could cause the A/C and the TACH to stop working? nothing else seems to be wrong with it, oh and now it's not going into O.D. again. Also there was a metal relay looking plug connected to a 3 pin connector under the dash next to the fuse box that was getting very hot. It is not the flasher relay or horn relay, does anyone know what that is for and why the case of it is getting around 120 degrees or so, so hot you can't even hardly hold it in your hand.

 

Here is a pic of what is getting very hot.

 

The part in the pic is the timer for the light around the ignition switch. Hot is normal for that piece. Is the truck charging?

 

Intercooled truck?

 

As far as I know the truck is charging, the battery was low and it was brand new, not sure if the battery came that way or not, so I am charging it up as we speak and I am going to see if it loses charge, I have a battery and alternator tester, the tester showed it was under 12v and the battery was at 55%. As far as intercooled, what do you mean by that? The tranny has a separate cooler aside from the radiator if that is what you are asking bubba. Oh and if the truck isn't charging would it cause the computer to bypass certain functions in order to conserve battery power? If that is the case, why would it cut the tach out of the loop? all the other gauges work fine. And why the "wait to start" light only when the truck is running, that light does not even come on when I turn the key to the "on" position, but it sure comes on when the truck is started up.

 

Intercooled is a cooler that your turbo blows through that goes to your intake. Does your turbo have a pipe that crosses over your valve covers to your intake? That would be non intercooled. If the pipe comes out of your turbo and goes to and through your radiator support it's intercooled.

 

It is intercooled.

 

I would check the auto shutdown relay. If that is not working the ecm will not know the engine is running. I think you have a bad ecm since the wait to start light is coming on. You can also clean and tighten the ground wire that goes from om the negative battery terminal to the radiator support. That ground is very important on these trucks.

 

Okay I will check that relay, there are only 3 on the inside drivers side of the fender, do you by chance know which one it is? I will check that ground right now and I know the battery is charged so it's play time. I will keep you all posted.

 

I cleaned that ground up and still no tach or A/C and the wait to start light comes on once the truck is started. I bought 3 new relays and they were not the problem. I am going to troubleshoot the alternator next. I'll keep yall posted.

 

What is the date on your door sticker and is your voltage regulator located on the firewall behind the head?

Mark.

 

My truck has this timer but I don't have a tilt column or the ignition ring light.

I oughta just unplug the thing and isolate the wires. Unless it somehow is a relay for something wired to the accessory position on the ignition switch.

 

After reading this, with the WTS showing and the A/C clutch being a high load component, I'd look at the fusible links.

Mark.

 

I'm still learning some of the nuances of the first gens, but didn't all intercooled trucks have the engine speed sensor?

If so, that would be the first thing I would check.

 

Have you recently painted the gauge needles?