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Old 01-13-2003, 02:27 AM
Registered User
Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
86 190E 2.3 - Tach, clock affected by fastening seat belt

Hello Everyone,

My sister just bought an 86 190e 2.3L. It was previously my aunts car who drove it very little and was always garaged. It has 77,000 miles on it. It's in prestine condition.

Anyway, it does have a couple of electrical issues.

Instrument cluster:
1. The clock works when the ignition is off. With the ignition on, it also works but as soon as you fasten the driver seat belt the clock stops working.

2. The tach works with the engine running. Like the clock, when the driver seat belt is fastened, it stops working as well.

The clock and tach are related I'm sure. I don't understand how fastening the seat belt affects it. When you release the seat belt, the Tach and clock come alive again.

I checked and replaced the fuses for the instrument cluster. I also checked the power feed for the clock behind the cluster. it gets 12.6V with the key off, on as well as the seat belt fastened or unfastened. I suspect perhaps a relay somewhere that supplies ground is faulty.

Another observation was that the seat belt reminder light didn't work. I thought it was the bulb so I replaced it. Still didn't work. This also may be related.

Driver power seat:

3. The driver power seat (w/memory) only moves forward and back, and the rear height adjustment works as well. the back rest, head rest, and front height adjustment do not work. When it move the buttons, you can hear clicking under the seat. The passenger seat has a similar condition.

I looked in the auxiliary fuse box and found a blue 25A fuse blown. I replaced it and the passenger seat became fully functional. The driver seat back rest is fully functional, but the head rest adjustment and front height adjustment going down continually blow the fuse. It doesn't blow when adjusting the front height up; only when going down. The head rest blows the fuse up or down.

I suspect maybe it's a bad control module under the driver seat or maybe the diode everyone talks about.

Maybe all 3 problems are related somehow. Any help would appreciated.


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Old 01-13-2003, 11:39 AM
it leaks, its german
Join Date: Mar 2002
Location: raleigh nc
Posts: 1,111
check your grounds and make sure the harness for the cluster is not shorted out to the cluster as well as checking the dome lamp harness at the lamp.

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Old 01-13-2003, 11:50 PM
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Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133

Thanks for the reply. I'll check those two items. I'll get back to you with my findings.

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Old 01-16-2003, 12:25 AM
Registered User
Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
Thumbs up It's fixed!

It's fixed!

I pulled the instrument cluster out and discovered it was previously opened. The tach sided of the cluster was not getting ground. The oil pressure/temp side of the cluster had a couple of burned traces on the board. How they got burned I don't know but it looks like someone soldered it back together. Both traces supplied ground to various places. One was the ground contact for the tach and clock as well as the seat belt reminder.

Still have to check on that power driver seat. Thanks again Joe!

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Old 01-21-2003, 05:43 PM
Registered User
Join Date: Jan 2001
Location: Tegucigalpa, Honduras
Posts: 5
Tach panel problem

Dieselguy, I have the same problem on my 1984 190E 2.0. This started after they changed my ignition key because it locked. How did you remove the panel?
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Old 01-22-2003, 01:51 AM
Registered User
Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
I inserted a coat hanger with a hook at the end. It had a slight curve to it could grab the back of the cluster. I simply let the hook catch the back of the cluster and pulled each side out slowly and evenly. It was tough getting the speedo cable off and on, but all you need is patience.
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