Coding plug headaches

[Spyke]

1987 (10-86 build) 325 eta

-No Odometer movement at all (Speedometer works fine)
-Tachometer always stuck at 2000 RPM when car is running
-Gears are new
-SI board has new batteries and checks out completely
-Ground for cluster is good


Coding plug is the only thing left, but is OF COURSE an NLA part, at least for my year. I found two small nicks in the PCB paths, but upon scraping the sealant layer off and reflowing, there was no change in behavior. Clearly these nicks are NOT the problem.

Anyone have any tips on how to repair a coding plug? Google is no help on the matter, and I don't want another 30 year old part.


IMG_7851 by Spyke e36/e30, on Flickr


IMG_7850 by Spyke e36/e30, on Flickr


IMG_7848 by Spyke e36/e30, on Flickr

[AndrewBird]

First off, the tach and speedo are completely separate units. One not working has nothing to do with the other not working. The coding plug has nothing to do with the speedo.

The tach stuck at 2000 rpm sounds a like a short somewhere on the tach input wire.

The speedo not working could be a bad sensor in the diff or broken wires near the sensor. The wires often get brittle and break.

[Spyke]

Wouldn't a problem with the input result in no signal? Tach being stuck at 2000 RPM seems like far too specific of a problem. [With the coding plug removed, the tach reads zero, and there's no movement on the econometer]

Speedometer works, the odometer is stuck. I have been told repeatedly that the odometer and tach issues I have are linked to one of the three following:

1) SI board - refurbished and checks out
2) Coding plug - ???
3) Cluster ground - confirmed good

[jlevie]

The issues you have will be caused by a bad speedometer and a bad tachometer. A bad SI board could render the tach inop and a bad coding plug could result in an inop tach or one that display correct engine speed.

[Gregs///M]

Gregg,

Since the speed works and the odometer does not, you can assume that the problem lies in the cluster itself. I assume you have newer odometer gears. Try loosening the plastic cover plate over the gears, when those two screws are tightened too much, it will prevent the odo gears from turning. If you never replaced the gears, definitely the problem. I have the gears in stock.

Your tach problems could be coding plug related but I rarely see coding plugs fail. However, its not impossible. Also, the "nicks" on the coding plug do look intentional. Damaged main cluster board could also be a culprit.

If you want to pull the cluster and drop it off at my place sometime, I'll take a look at it for you. I have tons of spare coding plugs that I can swap out and let you have. I can get the cluster working, or at least find exactly what is wrong with it.

You can see my new cluster tester in action!

Greg

[kevpatts]

Hey, sorry to resurrect an old topic here, but this is the closest I've seen on the Internet to what I need.

A long time ago I swapped the original cluster out of my 316 (not 316i!) with a 2nd hand one but I never swapped my original coding plug in.

Anyway, my cluster is the 316 one with the clock instead of tach, so does it need a plug at all?

Now I'm swapping in another new cluster and don't know which plug to use. I have BMW18 (1385 364) and BMW02 (1377 362).

Seeing as I have no tach, does it matter? If not, why are they in there in the first place? Is it possible my original one didn't have one at all (I've seen some online without this port at all).

Kevpatts

[Gregs///M]

Hey, sorry to resurrect an old topic here, but this is the closest I've seen on the Internet to what I need.

A long time ago I swapped the original cluster out of my 316 (not 316i!) with a 2nd hand one but I never swapped my original coding plug in.

Anyway, my cluster is the 316 one with the clock instead of tach, so does it need a plug at all?

Now I'm swapping in another new cluster and don't know which plug to use. I have BMW18 (1385 364) and BMW02 (1377 362).

Seeing as I have no tach, does it matter? If not, why are they in there in the first place? Is it possible my original one didn't have one at all (I've seen some online without this port at all).

Kevpatts

Since you have the clock, you do not need one. Coding plug is for engine speed translation for the tach and mpg gauge.

[kevpatts]

Okay, another question. I have a tach dial spare somewhere. If I put it in, which coding plug should I use for a 316? I found another one I have BMW01 (1377 361)

[Gregs///M]

1377 361 is the M10 4 cylinder coding plug. So yea you would use it if your spare tach is the original redline used on your car.

[kevpatts]

Gregs,

I love ya man! While I have your attention, one more cluster related question: My speedo always says I'm going 7Km/h faster than I'm actually going (compared to speedo app on iPhone and speed warning signs on the street). The storage thing is that it's the same 7Km/h error no matter what speed I'm going, so it's not a linear error. My old cluster always said I was doing 15Km/h more than I was doing (it was in Mph though, new one only shows Km/h), so I don't think the problem is in the cluster.

Any ideas how to fix?

[Gregs///M]

5 or so MPH over the reading is normal on most BMW's.

[Gregs///M]

Gross incorrect speed reading is probably because the speedo is not matched to the sensor in the rear differential. The k=xxxx reading at the very bottom is the calibration factor, which is associated with the sensor in the diff.

[kevpatts]

Is there any way to correct/adject this? It was accurate a year ago before it went off the road for a restoration work.

[Gregs///M]

http://www.e30tech.com/forum/showthread.php?t=73541

[kevpatts]

Thanks man, that's a lot of info, but I don't think it's the same problem as mine. He says that his error is proportional to his speed, and he tweaks the scaling pot ("The trim pot (potentiometer) controls a scaling factor").

My error is 7Km/h when I'm going 20 and 120, so a scaling correction won't fix that.

I'll have a good search for similar problems, just thought I'd mention it while you were giving me your time.

Thanks a million for your help.