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Discussion Starter #1
Hi all,

For the last few days I’ve noticed my windows and sunroof have been working intermittently, a few times the windows would be stuck down, a few times stuck up. When they aren’t working all of the switches seem to be dead, and they are not illuminated (same with sunroof switch). It wasn’t until it rained yesterday that I noticed my wipers also were not working, I’ve done a lot of reading and it’s led me to the general module. I’ve already checked the window fuse in the engine bay and it’s ok. The 80a fusible link is ok too, took it out and it looks good as new, also I replaced it with some copper wire and connected both leads together and still no difference. There is 12.6v present at the fuse.

I removed both the GM and RM and had a look inside, visually they both seem to be ok, I couldn’t identify any burns or obvious signs of damage but of course that’s not a thorough diagnosis. Also worth mentioning when shutting the engine off, the RM will click at random intervals, probably 15-20 times within a 10-15 second period. I’ve found countless threads on here and other forums about this very issue, but none of them actually ended up reporting an actual solution to the problem, except one thread on here where the guy had the capacitors changed. Is there any definitive way to test this module or should I look at replacing the capacitors? I’ve had a look on eBay and there seem to be replacement units around the £130 mark but I don’t want to go spending money changing things that don’t need to be changed. Any advice would be greatly appreciated
 

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I know it ain't much of an advice, but don't forget to check the ground as well. It doesn't have a fuse, so may be a bit of a hassle to trace and check.

Changing capacitors is an easy task, if you're comfortable with a soldering iron. These are relatively large, so you don't have to be a soldering master. They will cost pennies in material, so it's not a significant cost to have them replaced. Pay attention to the varnish though, you will want to scrape it off the soldering points, before trying to remove the old caps. Also, pay attention to polarity, when you install the new ones.

Good luck
 

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I don't think I have anything to offer except for maybe to check the trunk lid wiring? Might be that enough wires are broken/corroded that it is causing that much havoc with the other systems?

I had my seats/windows die the other month, and it was my 80A fusible link - looked fine on visual inspection but had a hairline crack in it. Sounds like you've eliminated that as a possible culprit, though.

Trevor
 

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Discussion Starter #5
I know it ain't much of an advice, but don't forget to check the ground as well. It doesn't have a fuse, so may be a bit of a hassle to trace and check.

Changing capacitors is an easy task, if you're comfortable with a soldering iron. These are relatively large, so you don't have to be a soldering master. They will cost pennies in material, so it's not a significant cost to have them replaced. Pay attention to the varnish though, you will want to scrape it off the soldering points, before trying to remove the old caps. Also, pay attention to polarity, when you install the new ones.

Good luck
I’m not the best at soldering however my dad has been doing it for 40+ years so he will definitely help me. Thankfully I managed to contact a fellow M5 owner who lives near me who is willing to let me try his GM tomorrow. If that sorts the problem then I’ll definitely look at ordering and changing capacitors. Thanks for the advice about the varnish, I’ll make sure to do that
I don't think I have anything to offer except for maybe to check the trunk lid wiring? Might be that enough wires are broken/corroded that it is causing that much havoc with the other systems?

I had my seats/windows die the other month, and it was my 80A fusible link - looked fine on visual inspection but had a hairline crack in it. Sounds like you've eliminated that as a possible culprit, though.

Trevor
Thanks, I’ll have a look at that for sure, would be very strange for all of those things to malfunction from a single bad connection but stranger things have happened. I’ll post a pic of the 80a, I did read that other people said it might have a minuscule crack that you can’t even see but will hinder its ability so I might just change it anyway for the sake of it.
941117
 

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There is a fuse block under the rear seat Drivers side under a plastic cover. I had the exact same issue on my car and one of the fuses had blown.
 

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Not to be too simplistic here, but have you checked the voltage of your battery. It is my understanding that a slightly low battery can wreck havoc on these. Check the date and load test the existing battery, a new one might solve the issues.
 

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Discussion Starter #8
slight update:

I decided to bite the bullet and buy a replacement general module off eBay with a matching part number, as all four functions that it seems to control have all died together so one would assume that the module is blown. Miraculously arrived in under 24 hours and I fitted it but still everything is dead. I’m going to see a friend/mechanic who also owns an M5 to see if he has any suggestions tomorrow.
There is a fuse block under the rear seat Drivers side under a plastic cover. I had the exact same issue on my car and one of the fuses had blown.
Yeah I’ve had a look at the fuses they’re all perfectly fine. There are also 2 relays I think a green and yellow which click when trying to operate the windows and sunroof but again no luck.
Not to be too simplistic here, but have you checked the voltage of your battery. It is my understanding that a slightly low battery can wreck havoc on these. Check the date and load test the existing battery, a new one might solve the issues.
My battery is fairly weak, it does need jump starting every few days but the issue is present even when the engine is on, alternator providing 13.6-14.4 volts
 
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