Mercedes-Benz W126 overvoltage relay and fuel pump relay fault
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Where is the W126 overvoltage protection relay?
The overvoltage relay is on the bulkhead next to the ABS box. Its housing is aluminium and it has a 10 A fuse. Next to it is the fuel pump relay, which is worth checking at the same time.
What symptoms does a faulty overvoltage relay or pump relay cause in the W126?
The solder joints on the relay's circuit board can crack and cut the pump's current. Symptoms are stalling, failure to start, or the pump running for a long time without pressure. Loss of power and jerking at constant throttle are also possible.
How is the W126 overvoltage relay or pump relay repaired?
A common fault is a cracked or burnt solder joint, which is resoldered. The alternative is to replace the relay with a good one. Only the correct relay suits the pump relay, and it must be checked by the relay number, because an aftermarket relay may not be suitable.
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