Glow plug unit
QI’ve been having a problem with the glow plug control unit on my 2008 Mercedes GL420 CDI. The glow plug symbol is staying on from a cold start until the temperature gauge shows about one third of normal running temperature and then switches off. It also lights up occasionally when the car is up to temperature – about every few weeks or so – possibly an indication that the glow plugs have been energised as part of the DPF regeneration strategy?
I initially assumed that one or more glow plugs had failed so got the ECU interrogated by a local garage I use which showed that two plugs were apparently defective. This had also happened about three years ago and replacement glow plugs fixed it then.
I left the car with the garage to get a new set of the correct Bosch glow plugs fitted. Got a phone call later saying that the same fault was present when the new plugs were fitted. The owner of the garage had then called a Mercedes specialist who told him how to test the glow plug control unit and these tests confirmed that this unit was faulty.
Simple enough to fix you would think – buy and fit a new Mercedes OE part and job done. But no, Mercedes in their infinite wisdom have decided to make this part obsolete and I can’t order one from a Mercedes dealer. I find it astonishing that Mercedes is withdrawing product support for a car which is just over 14-years-old and which is in otherwise very good condition. The youngest cars of this model range are only about 9-years-old!
Aftermarket suppliers are limited to BERU who offer part no. GSE118 and Champion who offer part no. CCU118. My investigations have uncovered that Champion make both their own and the BERU ‘badge-engineered’ versions and that Champion have discontinued making them. Not very helpful.
I have spent hours scouring the internet in a vain effort to buy a new OE part or an aftermarket one. I have managed to find a UK breaker who has two used OE control units in stock tested and guaranteed for three months but I’m reluctant to go down the used electronic component route for obvious reasons unless I absolutely have to.
The OE part number on my car is A6291530479, later superseded by part number A6291530679. Would you have any contacts who could sell me a new OE or aftermarket part by any chance?
Can you tell me please how vital the glow plugs are on this engine? Being directinjection, I would imagine that glow plugs aren’t really needed to start from cold unless the weather is extremely cold? And if the glow plugs are working on 6 of the 8 cylinders this might be sufficient even in the coldest weather?
I know that they stay energised for a few minutes to (presumably) reduce emissions when the engine is starting to warm-up from a cold start. But what I need to know is whether or not the glow plugs are needed on this engine to help DPF regeneration? If not, could I safely ignore the glow plug control unit if I run out of used controllers? If I can’t source a new unit I will buy and fit a used unit from a scrapped car and then send off my original unit to a ECU repair specialist to see if they can fix it and keep it as a spare unit. If my unit can’t be fixed, I’ll buy the other spare unit from the breaker and keep it ‘just in case’.
Danny Gillis
A
From the information I have there are a few sources who can supply the controller, but as you have discovered most are showing out of stock. This will often mean that the part may not be available for the company to re-stock and so going on a wait list may be a lost cause.
It would be wise to replace the controller as the vehicle systems do depend on the correct operation of the glow plugs. Whilst if they fail it may not be immediately detrimental to the starting or the DPF regeneration, the constant and unwanted feed to the glow plugs may cause harm.
Hopefully as the old unit is confirmed to have failed, this unit can be sourced solving the problem.