Bad Tachometer Or Ground Issue?

[Jace78]

I have an odd issue, just bought my 3rd fox body (1990 5.0 LX) and "the only thing wrong was the tachometer stuck at 4000 rpm". I searched and read and decided to try resoldering the connections on the back of the tach. This fixed the issue for 2 drives, now stuck at 4,000 again I am leaning towards a possible ground issue but I am more mechanically inclined and electrically stupid Other symptoms are quiet door and key chime as well as I get static thru the speakers when rolling the windows down/up. I am debating upgrading the grounds off the engine tomorrow if it will help, also maybe tearing the dash apart again Any ideas/thoughts appreciated!!

<<edit>> stock ignition, 95a alternator, stock coil, no msd box etc, car fairly stock for the moment.

 

[89BlackGTvert]

Deff sounds like ground. Clean the negative battery cable.
Sent from my PI86100 using Board Express

 

[Jace78]

Thanks, will give it a go and give an update tomorrow.

 

[JordanB21]

cutting and cleaning the wire that connects to the negative terminal is what I had to do when my gauges were not working and moving around. Either attach another ground or clean and reterminate the original ground. and hope that'll do it.

 

[Jace78]

So, had a busy day today. Hunted down and cleaned all grounds. Added a 4g ground wire from the battery to frame. Tach still stuck at 4k. Took apart dash again and reslodered connections on the back of the tach, again. Put everything together and MONEY!! went to pick up daughter from school (she loves the car) and no blinkers....after hunting a few hours found some wires loose in the dash and now EVERYTHING WORKS!! even the power mirrors which I had wrote off. Thanks for advice and the previous good info that had been posted got the car timed at 14* BTC and no pings, stable idle, now waiting for the plugs, rotor, cap and wires to arrive!

 

[JordanB21]

great tune up stuff, and glad you found it.
Always good to have extra grounds even if that wasn't the related problem
and knocked out another problem at the same time. cheers

 

[My92Vert]

So, had a busy day today. Hunted down and cleaned all grounds. Added a 4g ground wire from the battery to frame. Tach still stuck at 4k. Took apart dash again and reslodered connections on the back of the tach, again. Put everything together and MONEY!! went to pick up daughter from school (she loves the car) and no blinkers....after hunting a few hours found some wires loose in the dash and now EVERYTHING WORKS!! even the power mirrors which I had wrote off. Thanks for advice and the previous good info that had been posted got the car timed at 14* BTC and no pings, stable idle, now waiting for the plugs, rotor, cap and wires to arrive!

Hey just wanted to ask where are the grounds on the back that you resoldered? My tach is stuck at 2800 and proceeds to go up as rpm increases. I had the dash out once and couldn't really see what was what. Since putting everything back together when I go over hard bumps or rough r/r tracks the thing looses power, once it settles down, it resumes. I'm getting a headache thinking about it

 

[Jace78]

There are no grounds on the back of the tach, I simply re-did all the soldering on the back. For the most part I just heated up the solder enough to liquify it then let it dry again. There were a few that it appeared needed a little extra so I did add some solder to the rest. It may help, but yours sounds more like a loose wire somewhere perhaps? I don't see what you could hurt by doing this though. When I get home I will post some good links that will help with what is back there.