1988 Mercedes Benz 420sl



May, 8, 2009 AT 9:39 AM

Electrical problem
1988 Mercedes Benz 420sl V8 Automatic 23,217 miles

After putting in a new battery, my windows and door locks don't work. All fuses are good, but one fuse has no power to it. Where is the relay reset? Or any other idea why this would happen?


2 Answers



May, 10, 2009 AT 8:37 AM

I have forwarded your question to our M/B tech. He will be with you shortly, thank you for your patience



May, 12, 2009 AT 11:58 AM

Look at the diagram below and help me identify which fuse is getting no power. Please note which number fuse is getting no power.

This is more than likely a power delivery issue as you stated. I would be suspect of fuse 15 which is an 8 amp fuse that controls seat features, central locking and a host of other accessories. Let me know which fuse is lacking power and I will trace back so we can nail down which component is causing the failure. I believe you probably have a dead relay on one of these circuits. Try this just for a quick test. Access your relay box, pictured below:

Relay "I" supplies power to the windows and "K" provides power to the antitheft sytem which includes central locking. I would like you to switch each of these relays with another of the same. Look in the relay box and find relay I and K note any identifying numbers (part number) on these relays. In the same fuse box there will be a couple of the same relays working for different components, I want you to switch one of these relays with another one from a working circuit. For instance the power window relay "I" should have the same relay as either the horn or headlamp washers. By switching the two you can identify if this is mearly a dead relay. Try the window relay then for operation. If all still does not work go to relay K and do the same. More than likely K will be a bad relay and will prevent power from being delivered to your non working components.

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