Intermittent Wiper Not Working

[clintman17]

I've written here about this problem before, but it's still an issue and there are new developments. If anyone can shed some light on anything, please do. It is driving me crazy.

Since I had my windshield replaced with Pilkington glass the intermittent wipers haven't worked. The reputable glass company came back and replaced the glass again and ordered and installed a new rain sensor and it still doesn't work. There are no bubbles in the glue between the glass and the sensor. After some research I thought it might need to be recoded. I took it to a BMW certified mechanic who coded it just fine, but it would not initialize. They never could figure out how to get it working.

Today I found a possible new piece to the puzzle, although I don't know what it means... The intermittent wipers work, only on the most sensitive setting, when the ignition is in the accessory position. However, if I start the car, even if they were working in the on position, the intermittent wipers stop working.

Anyone have any ideas?

[bcworkz]

Perhaps the power relays? I believe one or two members had issues with these. They are behind the fuse panel behind the glove box. IIRC there are two of them. In general it seems BMW relays are not the most reliable devices.

[clintman17]

I heard it could be the relays. Is there an easy way to test to see if this is definitely the problem? Are these relays something that are relatively easy to change on ones own?

[bcworkz]

Well, the wiper relays just plug in AFAIK. But on further thought, if only the intermittent function is not working, and the regular speeds are working properly, I don't think the problem is the wiper relays but relays on the GM5 control module.

One wiper relay manages power to the motor, the other manages the reversing function, best I can tell from the sketchy wiring diagram. The delay function appears to be managed by GM5. I've no idea if the relays on that board are even involved, but I do know many people have had problems with GM5 relays, usually related to central locking.

BMW considers the entire module replaceable and will not even attempt repair. I know there is an outfit in the UK that will repair these modules, I would expect something similar is available in the US. Repair is potentially DIY if you have reasonable soldering skills and some basic electronic diagnostic equipment. You would also need to source the actual relays. You would need the associated data sheets just to be able to identify what terminals do what for testing.

That said, there still is some possibility in my mind that the main relays can have issues under intermittent control and work OK at regular speeds. Testing for this could be difficult since they work part of the time. DIS provides for some limited test functions that may provide more clues. They could be removed and bench tested, but you would need to determine which terminals do what. Data on proper resistance through the coils would also be useful.

For lack of better information, it may be worth just replacing the wiper relays to eliminate that possibility before pursuing GM5 repair, they're not all that expensive in the overall scheme of things.

[Tthisistylerr]

Did you ever get this sorted? Was it the rain sensor in the mirror?