Hi guys, I was idling longer than usual the other day about 45 min. When I got back in the truck I noticed the a/c hotter than usual and my tach dancing between 0 and 750 with brief periods of all my interior dash lights coming on like if my truck had turned off; while all this was happening inside my truck was idling normal like if nothing was happening. Once I start rolling the a/c comes back to normal and my tach stops dancing. Now it's happens all the time when I’m idling; please help..

 

alternator bad or loose connection?

 

I'm checking the alternator tomorrow but the gauge reads fine.

 

Could be your crank speed sensor. Bad/broken wire, out of adjustment, etc. If the PCM sees no signal from the sensor, it assumes the truck is off, so the AC will stop working, and the truck will quit charging.

 

If you can, avoid long idles. It is bad for the motor. AC may be a little low on coolant?

 

Thanks guys, I just got around to changing my crank sensor and everything is back to normal - woohoo.