Electrical switches failing one at a time

[ilike325i]

So I was in the woods with 95' 740i and hit a rock which took out the drive belt and cracked tranny drain pan. Had to get down from the mountain and into cell range so I milked it about 15 miles or whatever while losing one system at a time as battery power slowly drained out. Fixed all and everything normal with car but then other day sunroof only will pop up, not retract or open. Then pass window switch stopped working a couple days after that, then passenger rear window a day after that, then driver rear window a day after that.

I realize the stress of driving on draining battery power on the electrical system but why the continuing, incremental failures? Is this due to some specific electrical component u think? Also battery is older and undersized for car. Could battery alone account for this? Thanks for any thoughts or ideas. Fortunately driver door switches all work fine as of now anyway.

[tylamb19]

So I was in the woods with 95' 740i and hit a rock which took out the drive belt and cracked tranny drain pan. Had to get down from the mountain and into cell range so I milked it about 15 miles or whatever while losing one system at a time as battery power slowly drained out. Fixed all and everything normal with car but then other day sunroof only will pop up, not retract or open. Then pass window switch stopped working a couple days after that, then passenger rear window a day after that, then driver rear window a day after that.

I realize the stress of driving on draining battery power on the electrical system but why the continuing, incremental failures? Is this due to some specific electrical component u think? Also battery is older and undersized for car. Could battery alone account for this? Thanks for any thoughts or ideas. Fortunately driver door switches all work fine as of now anyway.

I would definitely start with the battery. Bad/low voltage really messes with these cars. For the sunroof issue, you have to reset the sunroof system by pressing and holding the "vent" or pop up feature of the sunroof switch for 15 seconds. After that, it will work. Freaked me out the first time it happened when I disconnected the battery before. For the windows, I would definitely start with a properly charged and properly sized battery. Is the problem with the switch limited to the driver's door switch, or is it also in the switches in each door that doesn't work? I would doubt that all the window regulators died within 2 days of each other.

Edit: just re-read and realized you answered my question already. Since it doesn't affect the drivers door switches, I would highly point to a bad battery or something like that. The window switches are all on the I Bus so since they are working I would say it is definitely not the windows. The I Bus relies heavily on correct voltage so definitely would recommend changing the battery out.

[chemmech]

I'd check the alternator make sure it's operating up to spec proper voltage etc. , running an alternator without a drive belt can damage or destroy it.....

[Mayorchuck]

In addition to the advice already given, those all work off the General Module. It sits above the passenger side floorboard, behind the dash. It is often a victim of water damage when the sunroof drains leak. When you look up there, it's the one with three connections. You can try unplugging them to check for moisture. Make sure the battery is disconnected when you do so. But again, you need to have the proper battery in this car. You can't really diagnose anything until you do.

[ilike325i]

In addition to the advice already given, those all work off the General Module. It sits above the passenger side floorboard, behind the dash. It is often a victim of water damage when the sunroof drains leak. When you look up there, it's the one with three connections. You can try unplugging them to check for moisture. Make sure the battery is disconnected when you do so. But again, you need to have the proper battery in this car. You can't really diagnose anything until you do.

That seems the most likely cuz this happened only after leaving sunroof popped up during minor rain (I closed the next day via Allen wrench under hatch in headliner). I can't figure out how to separate the covers that the general module sits behind. There is a white plastic cover And black metal cover that join together. I unlatched the two white plastic latches on the side of the white cover that holds the metal black cover, but there is not enough room to slide out the black cover. Surely there must be a simple way to separate the covers that I'm missing?

[Mayorchuck]

The GM just sits on a shelf. Just unplug the connectors and pull it out. abs.jpg

I just noticed you have a '95 so it may look a bit different. I have never owned a '95 so I don't know if the setup is any different or not. This is from a '96. I know the '95 has a Light Module and a Check module that was replaced with a single Light Check Module in '96. I don't recall there was any changes to the GM.

[Mayorchuck]

It seems the '95 GM is near the Light module so my info above is not applicable to your car. I found a pic within this forum post.

http://www.bimmerboard.com/forums/posts/473258

https://www.bimmerforums.com/forum/s...9#post13621759

[ilike325i]

It seems the '95 GM is near the Light module so my info above is not applicable to your car. I found a pic within this forum post.

http://www.bimmerboard.com/forums/posts/473258

https://www.bimmerforums.com/forum/s...9#post13621759

Ahh I see. Thx much for that info! Looks like removing glove box might be the key. I think glove box is the thing that prevents black metal cover from having enough room to slide off, exposing the gm (guessing). I'll post up some pics after digging into it. Will swap batteries also to see if that makes a diff. Coming down the mountain with heat on so as to not overheat and keeping speed up, I had concerns that I was stressing out electrical system, so could well be alternator as mentioned above or something else but the rain in sunroof timing makes me think gm is the likely culprit.

as an aside, the few times something has gone wrong with this car I always think, "I should just sell it", then after I fix whatever it was I think, "this is the best car in world, and so inexpensive I should keep it". Ha ha

[ilike325i]

Well it looks like the new battery did the trick. At least for now all is normal again. Thx Tylamb19 for the hint on the sunroof as that fixed it!

The battery I had in it was very old and very undersized so it was pretty crappy to begin with but then running without alternator kind of put the nail in the coffin I guess. kinda weird though because car started ok with that old battery (after charging). Probably for the best to replace it anyway with winter coming on.

I wouldn't totally rule out the general module moisture possibility either cuz it could be that it had a chance to dry out in the meantime. I'll clean the sunroof drains just in case.

fyi 2008 dodge sprinter diesel battery specs are almost the same as oem 740 battery specs but it is much less $.

Also in regards to the module location on a 95' here is the plastic and metal cover I was talking about. I assume the module is behind that but never actually took apart to verify.

07ACFCA2-10F2-4898-A95D-1A9AC663D9A6.jpeg

[tylamb19]

Well it looks like the new battery did the trick. At least for now all is normal again. Thx Tylamb19 for the hint on the sunroof as that fixed it!

The battery I had in it was very old and very undersized so it was pretty crappy to begin with but then running without alternator kind of put the nail in the coffin I guess. kinda weird though because car started ok with that old battery (after charging). Probably for the best to replace it anyway with winter coming on.

I wouldn't totally rule out the general module moisture possibility either cuz it could be that it had a chance to dry out in the meantime. I'll clean the sunroof drains just in case.

fyi 2008 dodge sprinter diesel battery specs are almost the same as oem 740 battery specs but it is much less $.

Also in regards to the module location on a 95' here is the plastic and metal cover I was talking about. I assume the module is behind that but never actually took apart to verify.

07ACFCA2-10F2-4898-A95D-1A9AC663D9A6.jpeg

No problem and I'm glad the tip fixed it! These cars are incredibly, incredibly sensitive to battery voltage and proper charging specifications, etc. If the windows started working with the new battery that's probably going to be the last of what you hear of it, until the new battery dies eventually. I would still clean out the drains and whatnot for some peace of mind but I have a feeling your complete problem was solved with the battery. Glad I could help out!