Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hello,Very often such symptoms are due to failure of overvoltage protection relay. it is located on the right side of engine bay, next to control units. Intermittency is due to cold solders on the electrical plate inside the relay.
Resoldering electrical plate can cure the issue.
Best Regards, Stan
Resoldering electrical plate can cure the issue. This relay is sealed and I don't see how to open it without damaging the relay.
I will have to replay the relay,...I assume.
replace the relay
The shaft rotation sensor showed faulty and was replace but was not a cure.
Another suggestion was the air mass sensor is faulty
To open the relay, the lower edge must be pressed off. To avoid any mixture getting in, some rubber sealant must be applied there. It is not a standard repair procedure but otherwise it is intended to be replaced.
When airmass sensor fails, usualy engine catches and runs poorly when cold. Also car has a lack of power or excessive fuel consumption.
I ordered a new over voltage relay, Beck Arnley BEC2030177, from XXXXXXXXXXXXXXXXX.XXX and they now tell me they don't have it.
The current relay in this auto is clean and seems to be relatively new. Should I order a handful of these?
The relay in the auto is clean and seems new. Should I order a handful of these?
I just ordered a Kaehler Mercedes Benz C220 Overload Relay.
whenever this c220 performs a "do not start", I replace the relay on the spot to see if that works.
Yes, that is a good plan. just make sure that the amount of fuses in both relays is the same
Let me know if i can help further with this, whenever is more comfortable for you. Best Regards, Stan
The only way I can test if this is the solution is to wait until the symptom occurs and then replace the relay. I think you will agree intermittent problems are tricky to diagnose. There is only one 15 amp fuse on the relay in this auto.
Ok, please get back to me once the relay solution is tested out. We can have this question open for as long as needed.
Stan, The went into it usual "no start" mode. I immediatly installed the new overload relay and the c220 still would not start.
One service shop, after looking into the database, found the brake failure monitor system will cause the Mercedes to go into "limp mode". This could be a suspected failed part.
Hello,Never heard of Mercedes due to problems with brakes. If overload protection relay and crankshaft position sensor did not solve the issue- car should be checked with Star Diagnosis computer when no/start issue happens. Only some independent Mercedes specialists have the tool. Possibly factory immobilizer is failing.
What about a faulty theft protection system?
I discovered a solution: Pull the key out of the start switch, get out of the car, lock all doors, open all doors, get back in the car, put in the key and start the car.
This works every time.
Hello, immobilizer is a possibility. It is possible to confirm it's failure with Star Diagnosis computer. Some independent Mercedes shops have it besides the dealers. On the other hand, cutting out when engine is warm is often associated with failing crankshaft position sensor.
Crankshaft position sensor was changed and did not cure the problem. $400 for a false diagnosis. Overload relay was also changed...another false diagnosis.
I'll stick with my solution at $0.00.
Excuse me for not remembering that sensor was already replaced. If you have a possibility, please connect a jump cable from car's battery negative terminal to engine ground and check if that affects starting. It might be a poor engine to body ground connection causing such problem.