'86 420 SEL Instruments Problem - PeachParts Mercedes-Benz Forum

Randy · #1 09-04-2010, 01:08 PM

Hi, guys, I changed out my broken odometer gears (thanks, Jeff Caplan) and I have the instrument panel back together. Now my oil pressure and temp gauges aren't right. They all do something, but the temp gage goes to max and the oil press gauge reads too low: about half way when driving, zero when idling, and it has a slight jigglr about once per second. The gas gauge seems right, as the tank is full and it goes to full when I turn the key on.
When I removed the round harness plug from the left side of the panel, the index pin in the center of the plug broke off, so I superglued it back on; otherwise I had no problems. Before I began this repair, the only prob I had other than a non-working odometer, was maybe the oil press gauge: it would peg at idle when cold or driving at any speed above idle; on warm idle it ran about midway, with a jiggle about once per second. I did not know if this was normal for the oil press gauge, but it aalways was like this as long as I owned the car. Advice?

david s poole · #2 09-05-2010, 12:52 PM

there are ground straps between all three instruments and it would seem one is not making contact.i have run a ground wire from metal screw going to main ground terminal behind instrument panel and cured this problem.

big dog 2 · #3 09-05-2010, 01:01 PM

My oil gauge, tach and clock acted strange after reinstalling my cluster too. I figured out the ground circuit was interuppted somewhere. My cure was the same as David suggested. I ran a wire from a screw behind the clock to a good ground on the wall behind the cluster and all the gauges and clock came back to life.

Randy · #4 09-05-2010, 02:31 PM

T
hanks for the information; I will try this and let you know how it works. UPDATE: SUCCESS!! Thanks David and Big Dog. I removed the cluster, and the speedometer after the needle fell off! I cleaned the ends of the metal strip across the bottom of the speedometer, because it looked like it might be a ground connection. I made up a light-gauge wire with two ring-type terminal endsn fastened one end underneath a screw on the clock side of the cluster and the other end to one of the ground points on the steering column structural support behind the cluster. Everything looks like its back to normal. I'll drive it to church tonight and try it out more thoroughly. Thanks aga

in, guys.

Randy · #5 09-05-2010, 10:30 PM

During a 40 mile round trip this evening, all instruments, including the odometer, worked normally. Thanks again!

big dog 2 · #6 09-05-2010, 10:50 PM

This ground issue with the cluster has come up several times in the last few years! Glad to help!

LandYaghtLover · #7 09-05-2010, 11:01 PM

I need to fix my fuel gauge, and my oil gauge bounces around. Once in a blue moon my temp gauge jumps.

So how does one exactly remove the cluster? I read about using knitting needles. Whats the best method?