This one has got me puzzled. "its not your typical bad ground"

There is no Fuel gauge and no Temp gauge. The OD light is illuminated and surges when the OD is engauged. There is no light when it is off (oppisite of normal operation). The spedometer surges when the OD is on and stops when the OD is disengauged.

This used to occur once every couple months. I could remedy it either by wiggling the conection on the back of the cluster or depressing the OD switch.

This time I started the car and it has been consistant for three weeks now.

Anyone ever traced a problem like this?

Where do I start?

I'm working on a similar problem on my 87 245. After determining my original speedo had a circuit board with a small hole burned in it, I replaced with a speedo from the junk yard. When I hooked it up and turned on the key it would peg itself out after a few seconds!! This is with-out even starting the motor!! Everything else works fine.

This speedo gets its signal in alternating current from the sending unit, which increases with speed but the highest ac voltage I've measured is about 5.5 volts. I'm wondering if I'm getting 12 volt dc "bleed through" into this circuit. Haven't checked voltage in a "pegged" condition yet as I ran outta time. I'm also wondering about a bad ground.

Any thoughts / comments are appreciated.

Read my Speedo Fried Post I left today.