Author Topic: Speedometer issues (among others) (Read 6072 times)

thedaddy · « **on:** March 27, 2011, 08:03:43 PM »

Took the cluster out because the water temp gauge was not working. It still does not work, but now the speedometer reads 20 MPH high. It registers 20 MPH while sitting still. I knew E30s were legendary, but that is fast.

What did I do to the speedo?

I still have not figured out the water gauge. I have read a lot about the SI board. My SI lights were working nicely previously. Where can a buy a rebuilt board?

Thanks for any help.

DesktopDave · « **Reply #1 on:** March 27, 2011, 09:00:22 PM »

I'd be tempted to take the speedo back out, get a plastic fork & pry that needle off, then just put it back at zero. I'm pretty sure there is a factory calibration method, but haven't an idea of a "how to."

All the SI lights are out? No oil change/inspection/etc lights? Pull that back out & replace the batteries. They're pretty easy to solder, I've even done it once or twice. Just be sure you match the type...older boards have NiCD and newer ones have Lithium non-rechargeable. No mix and match for these two types. I might have a spare around, just rebuilt one for my 325i.

EBay has rebuilt units, but I'm unsure of quality so I don't have any sellers to recommended. I just grab the soldering iron & put the new ones in. Good cells are only about $7 each or so.

If you need any gauges, they all seem to swap. I'm told that the Motometer & VDO components don't swap but I'm not 100% sure on that.

thedaddy · « **Reply #2 on:** March 27, 2011, 09:03:52 PM »

Actually I did just nudge the speedometer back to where it should be.

I am having a hard time with fuse 10. It just keeps blowing. I thought I had it narrowed down when I took the bulbs out of the reverse lights, but it just blew again.

I am already about done with BMW gauges. Who makes after market stuff? I know I can do an old school manual water temp gauge pretty easy, but the others would be tough. The Germans can engineer some great things, but they cannot wire for shit.

colin86325 · « **Reply #3 on:** March 28, 2011, 09:59:37 AM »

IIRC, fuse 10 goes to the backup switch harness. It frequently shorts out against the tranny or shifter linkage. Pull the shifter boot up and take a look.

thedaddy · « **Reply #4 on:** March 28, 2011, 11:00:04 AM »

Quote from: colin86325;102648

IIRC, fuse 10 goes to the backup switch harness. It frequently shorts out against the tranny or shifter linkage. Pull the shifter boot up and take a look.

I pulled the shifter boot, but all I saw was the window switches. I did not want to tear up the console too much. Because it was popping previously when I went into reverse I took the bulbs out of the reverse lights. Then it popped less, but still did over time.

It all started when I had someone work on the water gauge. Coming home from school today I disconnected the right plug from the cluster (blue IIRC) and drove for about 45 minutes before it popped fuse 10. The gas gauge bounces a little every now and then.

I read where lots of people have SI board issues, but the lights seem to work appropriately on that. I am at a loss. I hate electrical issues. I can deal with control arms and bushings and the things that make cars fun, but electrical crap is just supposed to work.

EDIT: I found the plug for the reverse light and unplugged it. Still popping fuses at the first moment of start up.

This all started when I took the car to the shop to get the temp gauge fixed. I cannot understand how changing the temp sensor (the one on the right to the gauge) could start all this. I was not popping fuses beforehand.

Any ideas?

thedaddy · « **Reply #5 on:** March 31, 2011, 08:39:54 AM »

EDIT 2:

New odo gears came in. While digging around in the wiring behind the cluster it became clear that is where a bare wire is.

DesktopDave · « **Reply #6 on:** March 31, 2011, 03:48:44 PM »

Did you fix the problem? Was it a problem with the cluster?

thedaddy · « **Reply #7 on:** March 31, 2011, 08:27:04 PM »

Quote from: DesktopDave;102741

Did you fix the problem? Was it a problem with the cluster?

I would not say fixed really.............I did get it to stop blowing fuses. Ultimately there is a short in the wiring right behind the cluster. A bare wire somewhere was touching something it did not like. We rearranged everything and it works fine now. I had to take the speedo out tonight to but new odo gears in so I will button it all back up tomorrow and when I do I will hunt for the shorting wire.

On a different note my housing has both the tabs on top broken off. Is there some magically way to fix those things with sheet steel, tooth picks and some diet Mountain Dew?

I have a second cluster with good tabs, but I hate the thought of moving my good and functional SI board from one to the other.

DesktopDave · « **Reply #8 on:** April 01, 2011, 06:13:00 AM »

I swap clusters & plastic all the time. 'Tis a necessity with our beloved e30's...the whole deal is only like 14 screws, you already have the speedo out...and the SI board is pretty robust. At work I have to repair laptops on occasion and I'd absolutely rather work on an e30 dash!

I'd say you're right on the money with the toothpicks, etc. Drink the Dew, chew on a toothpick & use a decent plastic epoxy with some thin scrap steel (I'd use 5 minute fast set). Since the tabs are hidden by the inner cover you could use just about anything with a bit of flex to fasten them., as long as the result isn't too thick to get back in the dash.

Too bad those cluster cases aren't styrene...otherwise some Testor's plastic model glue would do the trick.

thedaddy · « **Reply #9 on:** April 05, 2011, 12:04:04 AM »

On a different gauge note..........how the heck do you get to the water temp unit the feeds the temp gauge?

I can see the one on the left that feeds the DME, but the other is hidden. Is there a secret special place to touch like there is on the ladies?

DesktopDave · « **Reply #10 on:** April 05, 2011, 07:14:30 AM »

I suspect you have to pull the intake manifold.

thedaddy · « **Reply #11 on:** April 05, 2011, 09:42:00 PM »

Pull the intake manifold to change a sensor? WTF?

I just heard from my mechanic dude about some new V8 uber piece of crap BMW makes that requires him to pull the intake to change the starter. I may slap the next German person I see.

thedaddy · « **Reply #12 on:** April 07, 2011, 05:38:05 PM »

I do appreciate the help Dave as I work through this cluster.

The odo works nice. I realize now the shop I paid to fix the gauge changed the temp sensor to the DME and not the one to the gauge. I have to change that. Now I am trying to figure out the tach. It seems to be reading about 2000 RPM low. The rev limiter kicks in at 4500 or so. And with 4.10 gears it is only turning about 2250 RPM at 70 on wheels and tires with an OD a little smaller than stock. Those numbers do not add up.

Why would a tach read low?

thedaddy · « **Reply #13 on:** April 29, 2011, 11:16:34 PM »

OK.........didn't want to start a new thread, but I have my gauges mostly figured out but the tach issue remains.

The M42 hits rev limiter at an indicated 4500 RPM. Of course it is supposed to rev to 6000+. Also the revs seem artificially low at freeway speeds.

So either the gauge is reading wrong or my car is the only 4 cylinder that red lines at 4500. I know there is the plug on the front of the cluster. What is that supposed to look like and what serial number should it have?

Thanks

DesktopDave · « **Reply #14 on:** April 30, 2011, 08:00:41 AM »

Hmmm. I'll bet you're right...it sounds like you have a six-cyl plug programming the tach for six-cyl. I thought BMW calculated RPM off the crank trigger, but they must count ignition events instead. Four sparks would be a full 720 degree rotation on an M42 but only 480 degree rotation on an M20, so the tach is showing you 2/3rds speed.

The culprit is a small white plastic plug on the lower right of the cluster (here's an EBay e30 cluster listing with a good pic), usually labelled 'BMW 17' or something. There are two tangs on either side, squeeze together & pull towards you to remove it. Some code plugs are mounted on the back of the cluster instead...they're a black cartridge in the 'steckier' opening. I'm unfamiliar with those, haven't had any yet.

It'll have a date stamp (hopefully like 90.08 or something, that's [year].[month] of production) on it too. Here's some good pictures off EBay for an '86 eta M20 code chip.