Help! E34 Instrument Cluster Repair / Need Info

[m3driver97]

I recently completed the removal and repair of the instrument cluster for my 93 M5. Problem was intermittent temp gauge dropping to the left so I was frequently driving without a temperature gauge reading (a little risky with this car).

Read all the forum articles on this repair (bad capacitors) and decided to go ahead and order the caps to replace the bad ones. Decided to try the removal procedure w/o removing the steering wheel (wiggle out between dash & extended steering wheel) which worked out fine.

Somewhere in the excitement of making this repair and the reinstallation of the instrument cluster gauge, I had forgotten to turn off the ignition key and the turn signals (I pulled the unit out between the wheel and the dash w/o removing the steering wheel or disconnecting the SRS) before I hooked up the battery. I was surprised at the size of the spark that I saw when I put the negative terminal back on the battery but completed the job and tightened up the connection. When I got back to the driver's seat, I saw that the ignition switch had been on, along with the left turn signal and the headlights. Turned the key off and put everything else back where it belonged.

The moment of truth was here. I started up the car and was going for a drive to see how effective the repair was in fixing the temp. gauge. The first thing that I noticed was a flashing SRS light (which I had never had before). Not sure how this happened as I never hooked up the battery until all 4 instrument cluster connectors were plugged in and locked and none of the SRS connectors or steering wheel were ever touched. Bottom line, after a few minutes of driving, the flashing SRS light went to a continuous-on SRS light and my temp. gauge started acting up again. Now I am worse off than when I started.

Here are my questions:
1). Is there any tool that I can buy which will allow me to reset the SRS light without going to the dealer? The Peake RS/SRS tool that I found shows that is for use in 1994-2000 BMW's only. Can't find any tool which will handle 1993 or earlier. Am I stuck going to the dealer? If so, what type of charge should I expect?

2). Where is the SRS "error" stored? Is it in the instrument panel logic, the ECU, or some other dedicated piece of electronics?

3). If I buy a used instrument cluster (blue-back unit) and swap out the PC board, is there any special procedure to move the coding plug from my current unit to the replacement PC board without causing yet another problem? I don't want the coding plug to get screwed up causing the mileage to get lost.

Thanks in advance for any help/guidance any of you experts can provide me...

Regards, Brent

[whiskychaser]

I recently completed the removal and repair of the instrument cluster for my 93 M5. Problem was intermittent temp gauge dropping to the left so I was frequently driving without a temperature gauge reading (a little risky with this car).

Read all the forum articles on this repair (bad capacitors) and decided to go ahead and order the caps to replace the bad ones. Decided to try the removal procedure w/o removing the steering wheel (wiggle out between dash & extended steering wheel) which worked out fine.

Somewhere in the excitement of making this repair and the reinstallation of the instrument cluster gauge, I had forgotten to turn off the ignition key and the turn signals (I pulled the unit out between the wheel and the dash w/o removing the steering wheel or disconnecting the SRS) before I hooked up the battery. I was surprised at the size of the spark that I saw when I put the negative terminal back on the battery but completed the job and tightened up the connection. When I got back to the driver's seat, I saw that the ignition switch had been on, along with the left turn signal and the headlights. Turned the key off and put everything else back where it belonged.

The moment of truth was here. I started up the car and was going for a drive to see how effective the repair was in fixing the temp. gauge. The first thing that I noticed was a flashing SRS light (which I had never had before). Not sure how this happened as I never hooked up the battery until all 4 instrument cluster connectors were plugged in and locked and none of the SRS connectors or steering wheel were ever touched. Bottom line, after a few minutes of driving, the flashing SRS light went to a continuous-on SRS light and my temp. gauge started acting up again. Now I am worse off than when I started.

Here are my questions:
1). Is there any tool that I can buy which will allow me to reset the SRS light without going to the dealer? The Peake RS/SRS tool that I found shows that is for use in 1994-2000 BMW's only. Can't find any tool which will handle 1993 or earlier. Am I stuck going to the dealer? If so, what type of charge should I expect?

2). Where is the SRS "error" stored? Is it in the instrument panel logic, the ECU, or some other dedicated piece of electronics?

3). If I buy a used instrument cluster (blue-back unit) and swap out the PC board, is there any special procedure to move the coding plug from my current unit to the replacement PC board without causing yet another problem? I don't want the coding plug to get screwed up causing the mileage to get lost.

Thanks in advance for any help/guidance any of you experts can provide me...

Regards, Brent

Cant help you with 1+2 but depending where you are somebody here has got to have something like Carsoft which will erase stored faults. Mine doesnt have SRS so I couldnt tell if it would work or not. With regard to 3, you can split the 2 sections of the cluster if the back section is still OK. That will leave your chip undisturbed- I have UK gauges but my chip still displays the original km settings. If the back section is shot I dont think its that difficult to swap anyway

[m3driver97]

Thanks for the response Whiskychaser. Hadn't heard about Carsoft before your note but I looked them up -- looks like their product connects to the BMW maintenance connection and to a PC serial port to extract and analyze fault information. Nothing on their web site about this product being able to deal with a SRS fault, although it might have this capability.

As to the coding plug, my concern was whether or not I could screw it up by moving it from one PC board (mine) to another similar board. It appears that it is simple enough to remove it -- 2 latching tabs. Just didn't know if any dealer magic ($$$$) was required to make the coding plug work with a different PC board.

I don't want to do anything that will make the coding plug lose the vehicle mileage because I then have a TMU vehicle which has less value in my estimation.

[attack eagle]

have you checked the sender itself after dropped needle to make sure you are not diagnosing a cluster error when the sender is failing? Checked engine grounds also?

[m3driver97]

Thanks for the suggestion, attack eagle!!

One of the first things that I did with this car was to check the wiring (as well as I could follow it) for any breaks at or near the temp. sensor. I also literally spent hours looking for all the places that BMW put the electrical grounds and probably found 80% of them. All were snug and none had any type of corrosion around them.

That's when I started searching the forums to see what else I could find out about this problem.

When I removed the instrument cluster, I found that I had the later version of the board (=> 09/90) with P/N 62-11-8-363-173. On the board, I found that the 1000uF capacitor had dumped the electrolyte on the circuit board. When I removed the capacitor, I tried to scrape the dried electrolyte off the PC board but it was like light tan plastic and didn't want to budge. Decided to leave it there since I figured that with my luck, trying to scrape this stuff off would end up permanently damaging the board. Replaced this capacitor and also the nearby 220uF capacitor with 25V / 105C versions and thought that would fix the problem. As you can see from the post, I had the same problem as before with the temp. gauge dropping off and then returning to normal.

Some more searching on this problem and electrolytic capacitors in general led me to believe that I still had the problem because of the dried electolyte remaining on the board where the capacitor had leaked. Decided to get more aggressive so I removed the 1000uF capacitor again so I could get a good view of the area on the board. Turns out that the electrolyte crap dried exactly over the 4 PC lands that go to the temperature gauge. My guess is that stuff was intermittently conductive and was shorting out the temp. gauge from time to time.

To scrape the electrolyte off the board, I decided to use something soft & non-metallic so I would be able to avoid gouging the board. I settled on a heavyweight plastic spoon (the kind you can reuse) and filed the end of the handle to a 45-degree angle. I used a large illuminated magnifying glass to see what I was doing and after a little practice, I found that I could actually scrape this stuff off without damaging the board. When I got the majority off I then was able to use the corner of the filed area to clean between the lands and remove the remaining electrolyte. I was amazed at how well this approach worked to clean the board. Hard to tell that there was ever a problem.

Finally I proceeded to replace both capacitors I had previously installed with new ones. Also replaced 2 of the 22uF 40V units with 22uF 50V while I was at it. Now the only thing to do is to reassemble the instrument gauge, reinstall it, and see if the temperature gauge problem is now fixed.

If so, I am down to the SRS light and I'll have to find a way to deal with that. I'll post the results here in any event...!!

[whiskychaser]

I havent seen your board. But what you might think is stuff dumped out of a cap may not be that at all, particularly if its a waxy substance thats a bugger to shift. So did you remove the cap and check with a meter to see if it was stuffed? Carsoft wont affect your coding plug or everybody and his dog would be after it I have a cluster sitting around doing nothing. If you want me to pull it apart and pm you pics as I go just pm me

[attack eagle]

did you meter out the sensor itself?
bentley has the impedence at 'cold' and operating temp if you wanted to check.

[m3driver97]

WhiskyChaser... you could be right about the capacitor... I can't be sure that the stuff on
the board leaked out of the capacitor or was there on the board for some other reason. In any event, if it were just a bad capacitor, replacing it should have solved the problem and it hasn't yet.

I'll put the instrument cluster back in tomorrow AM and test it. Too dark in the garage at the present time. I'll post the results of the install.

Thanks for your feedback...!!

[shogun]

Peake SRS tool does not work on your E34, only on cars produced from 1994.
I have the SRS reset tool for your car for sale, new
http://www.bimmerboard.com/forums/posts/551746
If you want one, send me a PM and I will give you my Paypal account.
I will be in Europe from September 17 for 2 weeks, If you need it urgent, hurry up and I can send it out immy after receiving your payment, otherwise in October when I am back.

Read this thread about cluster repair
http://www.bimmerboard.com/forums/posts/569898
we soldered this:
http://www.bimmerboard.com/forums/posts/569942
connectors for the plugs, but inside the cluster, you have to break out a part. As you can see from the pics.
And see this
http://www.bimmerboard.com/forums/posts/467642/

[m3driver97]

attack eagle: Sorry I didn't respond sooner to your suggestion but I got tied up working.

The temperature sensor with the specs in the Bentley manual is the Engine Coolant Temperature Sensor (blue body) which only feeds the ECM.

The unit that feeds the the Instrument Cluster gauge is referred to as the coolant temperature gauge sender and has a brown body.

I have cleaned the connections on both of these gauges several times and have put Permatex dielectric grease on the connections to ensure no corrosion.

I can't be sure that I don't have a damaged wire somewhere between the sending unit and the instrument cluster, but the gauge always works until the car starts to get warmed up. It's only when I am almost at normal operating temperature that the gauge may decide to drop off to the left. So although a damaged wire isn't out of the question, I don't have it high on my list of suspects at the moment.

The second replacement of all the capacitors after I managed to scrape the electrolyte off the board also didn't resolve the problem. Just put it together this afternoon, went for a drive, and had the same exact problem.

One of the forums I looked at had a very similar problem which remained after the replacement of the capacitors. The person stated that the problem was finally resolved after the LCD display assembly was replaced.

I plan to buy a used instrument cluster on eBay, plug it in, and see if my temp gauge works OK. If so, I will swap whatever parts that I need to into my cluster until it starts working reliably. If not, I'll rewire the temperature sender to the cluster connector.

Thanks again for your suggestions...