W202 Electrical Fault
 

I have a weird problem with my 1998 W202 C200.
Initially just the BAS/ASR light would come on and the fan would run.
But now the water level and oil level lights are flickering plus the temp gauge and tacho are jumping up and down. And the gear changes are really rough - I guess because the tacho signal is erratic.
Engine is fine, brake lights work.
Help - any ideas?

I assume you did not scan for codes? That said, I think maybe more than one culprit. The dash issues can be = FIX: Dashboard not working, vibrating needles solution here! | Mercedes-Benz Forum (benzworld.org)

It can also be the battery/alternator. Measure the battery voltage with the car off.

I do not have a code scanner.
The needles do not vibrate - they drop to zero when the lights flicker on.

Battery voltage is good - standing - 12.75V. Running - 13.9V

https://cimg9.ibsrv.net/gimg/mercede...c58019c018.jpg
This is what my dash looks like when I am driving. Yes the engine is running.

Looking at the dash, and the fact that your engine seems to run fine, my bet is on water ingress on the front SAM. You would need to get to someone with a scanner to confirm the code, or go by trial and error and remove the SAM and have a look for telltale water damage.

What is this SAM? We haven't had rain for a while.
These are the codes I received using hfmscan after a 4km drive. I cleared the errors before the drive.


06 07 2023 11:42:39 AM

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097, Stored, ACTUAL
Fault in CAN communication from HFM-SFI control module.

Verify module, and replace if necessary.
Internal Resistance : 115-125 Ohm.
!!! Only USA !!!
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098, Stored
Fault in CAN communication from ASR control module.

Verify module, and replace if necessary.
Internal Resistance : 115-125 Ohm.
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150, Stored
CAN: no reception from transmission control module (N15/3)
Diagnosis Manual Chassis
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151, Stored, ACTUAL
CAN: no reception from air conditioning/automatic air conditioning (N19,N22)
Diagnosis Manual Climate Control
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152, Stored, ACTUAL
CAN: no reception from instrument cluster (A1) AD07.51-P-6000-41A
Diagnosis Manual
Information/Communication
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159, Stored, ACTUAL
CAN: kno reception from EIS AD07.51-P-6000-41A
Diagnosis Manual Body

Is there a mechanical switch or contact in the EIS ignition switch?
The faults that seem to be solved by wiggling the key fob.

You are going to need a good scan tool, not one for $65. You need a tool to read ALL of the systems.

Well - I am thinking if there is a mechanical contact and not just infrared or inductive then I can use some contact cleaner to solve my problems.
That is why I am hoping someone who has taken a switch apart can help.

Maybe a bottle of Marvel's Mystery Oil?