[sleepy hollow]

So, my wife's CLK320 (110K miles) has been sitting during this COVID thing; not getting a lot of driving. I replaced the battery when it failed to hold a charge (7 years old, so expected).

Recently got around to replacing the passenger side valve breather gasket to eliminate the occasional drops of oil landing on the manifold and offering that pungent burnt oil smell through the cabin air cleaner. Done. Problem solved

Now I am getting four errors showing up all of a sudden:

• check coolant level
• check wiper fluid level
• bad right front turn signal
• -40F degrees on the main display all the time

The right front turn signal does not light (fast blink when activated, but side mirror and rear light work fine). I replaced the bulb with a spare that had been sitting in the glove box for years, and it still does not work. Could be a bad replacement bulb, so I will next check with the bulb from the left turn signal, and/or buy a new one.

But, the washer fluid is full and so is the coolant reservoir. I topped both off just to be sure.

Finally, there is evidence that some mice have been chewing as I see some foam bits that have been chewed and a group of ground wires screwed to the top of the right fender have been chewed. We live in a rural area and have plenty of field mice to try to fend off especially during the spring and fall. My truck usually has tiny shell deposits on top of the engine that testify to the issue. It is parked outside. The Benz is garaged, but that is far from foolproof of course. Recently I was doing some overnight work on my truck (axle seal and ball joints) so the Benz sat out overnight, pretty rare occurrence. Though they never ave done this in 15 years.

I note that the ambient temp sensor, coolant reservoir sensor, and right blinker are all on the right front side of the engine. I believe the washer sensor also comes from that side even though it is on the left center.

Q: Anyone have advice on how to troubleshoot? Perhaps a common ground/wire harness, etc.? Anyone have diagrams to assist? I know I can do the tracing and try to reinvent a wheel, but it would sure help to get a few clues/hints, etc.

Thanks for any advice.

 

[Benzyle]

The washer level sensor and coolant level are on the exact same circuit..and yes the temp and right blinker are in the same area ..so I think you are right when you blame mice chewing wires.
Probably you have to thoroughly check and repair all the wires.....fast blink is due to incorrect resistance on the circuit...
No other way that I know. Maybe check the front SAM and fuses etc for any visible corrosion or damage as well.

 

[sleepy hollow]

Thank you for your reply. I will be attacking the problem over the weekend and will let you know what I find.

 

[sleepy hollow]

Well, mystery solved. I was not getting any voltage in two of the 5 battery side connections on the headlight assembly connector (I figured one of those might be a ground). I also was getting no voltage on the level sensor at the coolant tank. I removed the right front tire, and then two sections of the wheel well. After inspecting all of the wires down to the front ambient temp sensor and headlight assembly, I could see no problems with the wire bundles. I did not bother with the washer level sensor as it was hard to get to and I figured the problem was not forward. So I started working back towards the passenger firewall. I removed the battery and battery tray. That is where I found the problem.

There were 4 severed wires in the bundle that travels from the right front of the car along the fender wall under the battery tray to the inner "double" firewall to the SAM on the left side. The breaks were right under the battery tray where there is a lot of corrosion and also near where mice had accumulated nesting material. Could have been either battery acid or critters or both.

So, I stripped the 8 wire ends, crimped the wires together, soldered them, and put heatshrink tubing on each. Then I re-wrapped the bundle and zip tied it to the fender wall (more loosely than before to accommodate the slightly shorter wires that broke). Finally, I put strips of black Gorilla duct tape on top of the wiring under the battery tray, so there is a layer of good quality duct tape between the battery tray and all wires under there down to the drain hole and up along the fender wall..

Replaced the battery and put the car back together. Turned the key and immediately got the correct temp and no error messages. Right turn signal works again as well. 4 problems - front right turn signal, coolant level check, washer level check, and -40 ambient temp indicator - from breaks in 4 wires. All cleared when wires reconnected.

 

[Benzyle]

Good job..well done...
and thanks for posting the solution..
reminds me of the cartoon,,,
'' I hate those meeces to pieces. ''