I have a 95 1 ton diesel. Recently i started up my truck to find that my ac would not longer blow cold air, and that my tachometer would no longer move. It stayed this way for 2 days, but on my way to work today the tach jumped up and got stuck at 1100 rpm, and a few seconds later started working fine. I then checked the ac to find it blowing cold air again. Upon leaving work, my tack and ac were broken once more. I am assuming this is an electrical problem of some sort, but am lost as far as what i should do. I've traced the tach sensor wire from my balancer all the way to my firewall wiggling it along the way, and gotten nothing. i have no idea what wires to check for the ac. I assume its not a fuse since they both started working again this morning, so what could it be?