No Tach and constant red-line buzzer
 

I appear to have a short in the gauge cluster somewhere. After sitting for
a while (months), the tachometer fails to give a proper reading, topping
out at 1000 rpm. As I rev the engine, the needle will approach 1000 rpm.
It will go slightly above 1000, then start bouncing around the 1000 mark.

The red-line buzzer is on the entire time. The car doesn't have to be
running. When the tach starts working correctly, the buzzing stops too.
The tone of the buzzer is affected by having things like the turn signals on,
or having other gauge lights on, making it sound like a ground.

I was able to stop the buzzing and get my tachometer working correctly by
taking out the gauge cluster and cleaning off the ground. That isn't working
anymore though. I can live without a tach, is there some way to stop the
dreadful noise temporarily?

I have cleaned off the contacts on my alternator, my battery terminals are
fairly new and have been cleaned off. I've cleaned the other grounds that
I could get to.

Removing the combination connectors and just having power to the gauge
cluster does not seem to stop the buzzing. I may still try disconnecting the
tach wire from the combination connector and have everything else
connected and see what happens.

Suggestions are welcome, though I may be somewhat limited in what I can
try. I'm about 230 miles from the shop.

tldr;

Tach isn't working correctly, and is causing the red-line buzzer to buzz all of
the time. How do I temporarily silence it so I can get it back to the shop and
properly fix it?

Thanks!

You may Get an answer ..IF you state which series of car you have.

(But I am guessing that the sensor on top of the rad is disconnected..that is IF it is an FC)

Its an 85, so an FB.

Found the issue(s)

I sat down with the wiring diagrams (very helpful) and traced all the wires and
traces on the gauge cluster to see where they were going.
http://wright-here.net/files/manuals...g_Diagrams.pdf

I took apart the gauge cluster again and sat down with my multi meter.
Checked every trace and found multiple with no continuity. I've temporarily
fixed those with alligator clips until I can get my soldering iron out and
properly fix the board. Some of the traces just look rotten.

The other part, and potentially causing more of the grief were the two brass
bolts on the back of the tachometer. They are used for measuring the RPMs
of the engine to tell the buzzer when to buzz. Basically, it appears that the
resistance increases as the RPMs increase, once the resistance is at a
certain point, the buzzer buzzes. When I fist tested, there was no continuity
between these bolts and the pads.

Infinite resistance = infinite RPMs = exploding engine = buzz!

Hope this is helpful.

Lol.."fist tested"!