PeachParts Mercedes-Benz Forum - HOW-TO: W126 Odometer Repair, Clock Capacitor Replace

Quote:

Originally Posted by Bullfrog (Post 3898209)

I soldered in 2 capacitors that I picked up from the local electronics shop. At first the clock only worked for 5min at a time. I noticed that I did not cut one of the leads short enough on the back side of the board and I'm guessing that capasitor was shorting out. Now the clock will keep perfect time as long as the ignition is on. Once the ignition is off I think the clock continues to run for around 4 hours before it stops. There have been various upgrades to the stereo system in the past. I am not stokum on electronics at all, so I'm wondering, does the power for the clock come directly from the battery, or do the capacitors power the clock when the ignition is off. Would they power the clock for 4 hours with no power at all. I'm thinking maybe someone in the past may have spliced wires behind the dash and the clock power is no longer continuous but should be.

I, like you, suspect someone messed with your wiring in the dash. The clock should have 12V regardless of key position and should always keep time. The clock takes about 20mA of power every second. I think there is some 200uF of capacitance there.

I'd put a meter on that power line going the clock (spade terminal) and see if you've got 12V there with the key off.

--Kris