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Old 11-05-2012, 08:22 AM   #1
JGood
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Odometer intermittently working, MPG gauge pegged

I just pulled my 87 325is cluster apart to replace the odometer gears last week. Put it back together, put 200 miles on it, no issues. Then the other day, the odometer stopped spinning again and the MPG gauge pegged at 40. I tapped the dash a few times, the odometer started spinning, but stopped .2 miles later. The MPG gauge didn't come back to life though. However, if I rev the engine to 3k or more in any gear, the MPG gauge goes from pegged at 40, to pegged at 0. Then when the RPM's drop below 3k, it goes back to pegged at 40. My speedometer works great, always has. My OBC works, and is recording accurate average MPG.

I figure something must be loose, or I have a bad connection or something. But when I had the cluster apart last week, I was looking for any bad solder joints, etc... and everything looked good.

Ideas?
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Old 11-06-2012, 03:30 PM   #2
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Did you check the voltages on the SI batteries?
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Old 11-07-2012, 01:55 PM   #3
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Odometer and speedometer and fuel gauge do not run through the SI board so dead batteries wont affect their operation. The same cannot be said about the tach, temp, and MPG gauge.

The intermittent operation of the odometer, while the speedometer works fine, is a sure sign the odometer gears have failed again. If there was cracks in the solder in the main cluster board, speedometer, or chassis wiring, both the speedo and odometer would fail at the same time.

MPG not operating is a sign of dead SI board batteries. Those should be replaced if they have not already.
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Old 11-07-2012, 01:59 PM   #4
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your gears are acting up. pull it apart and see which one is jamming or cracked.
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Old 11-07-2012, 07:06 PM   #5
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The gears are fine, I just replaced them all with new ones last week.

I pulled the cluster apart, and after 2 hours of trial and error of swapping parts from spare clusters, I determined the SI board itself is fried. The batteries are good, still putting out 3.0 volts each.

Check this out:




See how some of the traces on the board are black? You can follow it from the SI board connection, up to the tach/MPG gauge, and also over towards the temp gauge. They are slightly burnt I think. The black wipes right off, but it surely isn't supposed to be there.

I pulled a spare cluster, and put my front cover with the SI board on the spare cluster, and it did the same thing after about 20 seconds, turned those same traces black. So I took a spare known-good SI board, and put it in my front cover, and put it on my cluster, and everything is working great. The MPG gauge is working 100%.

Of course, this all took longer then I'm making it sound, and I somehow managed to ruin 3 light bulbs on my cluster in the process. I think everything is just so old and brittle after 25 years, that if you even look at it wrong, it fails.

I don't know if this explains the odometer intermittent problem, since sometimes it works fine for 50+ miles. I'll know in a few days. I spun the gear by hand for a few miles, and there was no friction or anything.
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Old 11-08-2012, 05:31 AM   #6
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The odometer stopped working twice on my way to work today. I hit the trip reset button, and it started working again each time. The MPG gauge worked fine the whole time.

I'm wondering if I damaged the motor removing the old brass bushing from the main drive shaft that goes into the motor. I tried to not pull on it too hard, but it did require some force.
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Old 11-08-2012, 06:43 AM   #7
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In reality, I don't think you CAN ruin the motor that way. It doesn't look like there's anything there that can get affected. My odometer does the same thing, BTW: I've taken it apart four times now. I'm waiting on the Garagistic gears, maybe they'll make a difference.
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Old 11-08-2012, 07:14 AM   #8
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Quote:
Originally Posted by nmlss2006 View Post
In reality, I don't think you CAN ruin the motor that way. It doesn't look like there's anything there that can get affected. My odometer does the same thing, BTW: I've taken it apart four times now. I'm waiting on the Garagistic gears, maybe they'll make a difference.
The Garagistic instructions specifically say not to pull on the motor shaft to get the brass bushing off, as it will damage the motor. They say to squeeze the bushing with a pliers to loosen it. I worked that thing for a solid 10 minutes and it wasn't budging, so I just pried it off, putting force on that shaft, pulling it away from the motor. It wasn't a ton of force, but more then I'd have liked. This is the third time I've replaced gears in an e30 odometer, I've never had issues afterwords like this.

Are your gears stripped? If not, I can't imagine new gears fixing anything.

I found this thread that details common odometer problems beyond the gears. I'm guessing I have an additional problem, and probably didn't notice due to the fact that the odometer gears were stripped anyway.

http://www.r3vlimited.com/board/showthread.php?t=95733
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Old 11-08-2012, 04:02 PM   #9
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Well, it is the brand new gears. None of the teeth are missing or damaged, they just don't mesh correctly, there is too much of a gap between the gears. It's only a problem at one area of the gear, where the teeth are ever so slightly shorter.



And yes, I did have the spacers installed, I removed them to make it easier to do the video.
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Old 11-09-2012, 12:31 PM   #10
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Quote:
Originally Posted by JGood View Post
Well, it is the brand new gears. None of the teeth are missing or damaged, they just don't mesh correctly, there is too much of a gap between the gears. It's only a problem at one area of the gear, where the teeth are ever so slightly shorter.



And yes, I did have the spacers installed, I removed them to make it easier to do the video.
Did you order the right gears? There are VDO and motometer gears and they are different. I've installed several sets from Gargastic, MM and VDO and all worked flawlessly.
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Old 11-09-2012, 12:49 PM   #11
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Originally Posted by Gregs///M View Post
Did you order the right gears? There are VDO and motometer gears and they are different. I've installed several sets from Gargastic, MM and VDO and all worked flawlessly.

Yep. Motometer gears, motometer cluster. I've used Garagistic in the past as well, no issues. I contacted them, they shipped me another set. I'll check the sizes with a caliper when I get them to see if there are any differences. I unfortunately already threw the factory gears away, so I can't measure them.
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Old 11-10-2012, 06:14 PM   #12
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Yes, the other companies who sell gears say the same thing. However, I must have taken apart a half dozen MM odometers by now and I can't figure out exactly what you would damage. I'll be glad to be corrected.
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Old 11-14-2015, 04:36 PM   #13
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I just spent about 6 hours today trying to figure out basically the same exact problem you where having OP. Thanks so much for posting this. I ordered some gears to repair the odo on my new convertible.. My gear was cut improperly, I spent the whole day swapping out mother boards, rebuilding another speedo I had laying around, all to find out my installation wasn't the problem, nor was the car. It was the damn gears.

I hope this picture will help someone at some point, this thread with no pics helped me 3 years later! As you can see, the bottom right gear would install just fine, but after driving a couple blocks it would become crooked like in the picture bellow. Here's a picture right after removing it from the car for the ~7th time today.
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Old 03-14-2017, 10:18 PM   #14
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MF'er!!!! I just installed a set for someone. I tried a set of gears with 3 different speedo's and the odometer just would not work! I discovered that one of the gears had burrs in between the teeth and the resistance was too much for the drive motor gear when installed. I had to slice material out so that the gears spun with little effort before it began working. I spend quite a bit of time on this as you might imagine. I just emailed Garagistic thinking it was a problem with this batch but remembered reading about others having the same issue and found this thread. I see this has been happening for years. They should have been aware of the issue but obviously didn't fix it.
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Old 05-11-2017, 01:35 PM   #15
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I'm still scratching my head around this issue....Moves free by hand ,new gears and everything works like it should including my OBC.......
So now i have to rely on my MPG to get and estimates on mileage and service intervals works...
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