BMW Electrics

[SCB]

Hope someone can help. I drive a 'J' reg BMW 525i. I am having trouble with the electric windows and electric sunroof. They only work intermittently. They either all work or none work. I am led to believe that the cause is a faulty relay, is this correct?
Can anyone tell me what relay it is? There are a few in the fuse box which is in the engine compartment but none are marked up?

Please help it is driving me mad. I am either driving with the windows open when it is freezing and they refuse to close or I am boiling up when they are closed and refuse to open.

[stanleyman]

It may well be a faulty relay or a bad fuse connection that could also be in the footwell. You will probably need a BMW or Haynes manual to identify it if there are no indications as to what they are, usually this is marked on a cover.

[SCB]

I have a Haynes manual but it gives me no indication of what relay it is either. Incidently, I had a new water pump fitted and the problem seems to have developed since then. If, when the windows and sunroof are not working, you stop the car and turn the engine off, they will all work again.

[stanleyman]

Does the manual have a wiring diagram? It does sound like relay trouble and you may have to find it by taking them all out one by one until you find the right one and check they are working each time. It is worth just checking each one is firmly plugged in anyway just in case it is loose.

[SCB]

Yes the manual does have a wiring diagram but only shows the relay. It doesn't show where it can be found though. I have checked each one is firmly plugged in also removed them one by one and still couldn't find the correct one. I am obviously looking in the wrong place. The one I require does not seem to be in the engine bay with the fuse box.

[stanleyman]

You might find them in the foot well near the steering or passenger side.

[loola]

It certainly does seem like a relay problem. I would say that it is the ELECTRONIC OVERLOAD PROTECTION RELAYS...the power windows, sunroof & central locking circuits are protected by two electronic overload protection relays. Each relay works in conjunction with a 30 amp fuse. The cutout limits are designed so that the GM will interupt the load before the fuse blows. If either or both relays are opened, the GM will reset them after 60 seconds. If relay opening occurs 6 times in succession (indicating a permanent fault), the GM will not reset (unless ignition is turned off, then back on).

[loola]

For location, look behind the glovebox.

[SCB]

Thank you very much, I will take a look and let you know how I get on. I will not be able to check until at least Friday though as it is pitch black by the time I get home from work. Thanks again.

[stanleyman]

Well thanks Loola, that seems to have solved the location and reason for the cutout. All that's needed now is to find the fault or overload! It could be a faulty or overloaded motor drawing too much current or an intermitent short circuit, the wiring diagram might help by disconnecting suspect parts to see if the problem continues.

[SCB]

Well I have finally got round to checking behind the glove box. Taken the glove box out and a few other panels.

I found a lot of wires and a lot of large plugs but could not see any relay?