Car is a 1994 W202 (very early W202 before SAM units, immobiliser, etc).
VIN: WDB2020182F083756
History is that after I replaced some doors, the time on the instrument panel normally resets to 01:00 every time ignition is switched off.
Very rarely while I have been looking at this issue, sometimes it keeps time after ignition switched off, but if I cycle key it goes back to 01:00 again.
Unfortunately my WIS only seems to have wiring diagrams for W202 after 1.6.1997 so I cannot find wiring diagrams on WIS.
I had a quick look in Starfinder and found a diagram for the instruments, this showed Connector 1 Pin 17 should have permanent live / Terminal 30 and this was providing power correctly. Saw an earth point behind the instruments which was in perfect condition, no corrosion or anything.
Where things get even stranger...
I was messing around and noticed if I turned headlamps on sometimes this would reset the instruments approx. 50% of the time. No issue with side lights, only with headlights. When the instruments reset themselves, the illumination would stay on without flickering.
While it was doing this, I decided to start opening and closing doors which gave me a bulb failure warning which vanished when I restarted the car. This only happened once.
After messing around a bit longer, the instruments wouldn't reset when I turned the headlights on.
Car has aftermarket Clifford alarm. This alarm automatically arms itself if car is unlocked and not started. Disarming the alarm resets the instruments.
Also turning key to position 3 resets the instruments (even if I let go before starter turns).
Swapped the battery with a known good battery just in case but it makes no difference.
If anyone had old WIS and can pull up a diagram for this instrument panel I would be very grateful.
My suspicion is that the actual issue is with the aftermarket alarm, but I will never be able to get wiring diagram for this, so I'm thinking to make my own terminal 15/30 feeds from a sensible location.
VIN: WDB2020182F083756
History is that after I replaced some doors, the time on the instrument panel normally resets to 01:00 every time ignition is switched off.
Very rarely while I have been looking at this issue, sometimes it keeps time after ignition switched off, but if I cycle key it goes back to 01:00 again.
Unfortunately my WIS only seems to have wiring diagrams for W202 after 1.6.1997 so I cannot find wiring diagrams on WIS.
I had a quick look in Starfinder and found a diagram for the instruments, this showed Connector 1 Pin 17 should have permanent live / Terminal 30 and this was providing power correctly. Saw an earth point behind the instruments which was in perfect condition, no corrosion or anything.
Where things get even stranger...
I was messing around and noticed if I turned headlamps on sometimes this would reset the instruments approx. 50% of the time. No issue with side lights, only with headlights. When the instruments reset themselves, the illumination would stay on without flickering.
While it was doing this, I decided to start opening and closing doors which gave me a bulb failure warning which vanished when I restarted the car. This only happened once.
After messing around a bit longer, the instruments wouldn't reset when I turned the headlights on.
Car has aftermarket Clifford alarm. This alarm automatically arms itself if car is unlocked and not started. Disarming the alarm resets the instruments.
Also turning key to position 3 resets the instruments (even if I let go before starter turns).
Swapped the battery with a known good battery just in case but it makes no difference.
If anyone had old WIS and can pull up a diagram for this instrument panel I would be very grateful.
My suspicion is that the actual issue is with the aftermarket alarm, but I will never be able to get wiring diagram for this, so I'm thinking to make my own terminal 15/30 feeds from a sensible location.