Stereo on = fuse melt = tach inop

[iChevy]

Hi,

had a perfectly working factory tach on my 79 k5. Fiddled with the stereo a little, got it to work and after about 5 minutes the music transformed into screeching noise and electric burning smell was noticeable. Tach then went to 4000 rpm and is now stuck there. There is a fusable link at the two cables that are attached to the firewall (in the engine compartment) that burned through. Replaced it and ripped out the stereo to keep it from happening again. Tach still stuck at 4000 rpm. When I turn ignition to on the tach needle moves for a second about 1/4 of an inch..then stays at 4000 rpm... Engine runs normal, all other electrics (power windows, locks, lights) work normally, except for the hazard switch but that is due to it being disconnected.

Any hints on how to go about this problem are greatly appreciated. I'd love to have my original tach working again...


Thanks!!!

 

[dyeager535]

The factory tach's I've looked at have a completely separate wiring harness. If it's not working, I'd be genuinely worried that it is fried.

It only has three wires...ground, 12V ignition power, and lead from distributor. Check as much of those as you can (not sure on that year fuse panel, later 12V ignition wire is probably powered by one of the mini circuit breakers on the fuse panel) and if you don't find anything obviously wrong, pull the dash and take the tach out, check the circuit board for obvious burnt components. Check that the three wires for the tach have continuity from one end to the other.

 

[iChevy]

Thanks. Ill investigate and keep you posted!

 

[4X4HIGH]

I have a complete factory tach gauge cluster from IIRC a 74, if needed PM me for a price.