If it's not a cluster/si board problem then what is it

[84318i]

My speedometer and odometer work fine for about first 5 miles and then stop. Speedometer needle starts jumping all over the range and then drops to 0 and stays there.

So, I put in another speedometer/odo unit and does the same thing. I then tried bypassing the SI board altogether and it still does the same thing. So, it can't be the SI board since it's bypassed altogether. Keep in mind, all other gauges work just fine.

Today I picked up another cluster, I found one from a 90 325i, so just for the heck of it I put that one in place. Once again all gauges work, I drove the car and speedometer was working fine for 5.1 miles and then started jumping all over the range and eventually dropped to 0.

Now I can't believe it's an SI/Cluster problem since I've gone through about 3 clusters.

What's the next step, where is the speedometer/odo getting it's signal, it's gotta be something other than the cluster

[ecorrea21]

My '85 318i was doing the same thing only on longer drives it would start to work again. every time I got back in same thing you describe. Well in october I moved from So. Cal. to Texas since then the speedo has been working just fine? so just go on a cross country drive it should be fine......
Seriously I also tried changing the SI board to no avail, but its more likely a short in the harness.

[84318i]

I've also heard about a possible bad connection at C101, but not sure where that is and if there is a troubleshooting procedure on this ?

[SWISS]

Geez people. JUST REPALCE THE SENDING UNIT!!!!!!!

[84318i]

Geez people. JUST REPALCE THE SENDING UNIT!!!!!!!

Ok, what's the PN# and location ?

[SWISS]

PN# 62161369905 and it is on the rear diff cover, only sensor there.

[84318i]

Thank you, maybe this is it .(http://www.bavauto.com//assets/produ...2161369905.jpg) , Now, is there a way to test it ? if not, than i'll just order a new one from the dealer tomorow.

[SWISS]

Thank you, maybe this is it .(http://www.bavauto.com//assets/produ...2161369905.jpg) , Now, is there a way to test it ? if not, than i'll just order a new one from the dealer tomorow.

That's not it. It is a gear driven sensor that outputs an electrical current relative to how fast it is spun. I suppose you could hook up a multi meter to it and find a way to spin it at a good RPM and it should read something.

[Ablice]

Thank you, maybe this is it .(http://www.bavauto.com//assets/produ...2161369905.jpg) , Now, is there a way to test it ? if not, than i'll just order a new one from the dealer tomorow.

If you want to throw it up on jacks or preferably a lift then you could have someone crank her up and throw her into first...and using a multi-meter...

[RichV]

But if it quits after a while, it is probably breaking down in heat. So it may test ok, but once the diff heats up, the signal may be erratic.

[84318i]

Swiss, pic is for the PN # you posted I just found it on the bav auto site
http://www.bavauto.com/se1.asp?dept_id=104 , am I looking at the right PN# ?

Ablice, RichV - makes sense, I'll go ahead and remove it and see what it looks like and order a new one.

[84318i]

Alright, wires and it's plug look ok



measured 8ohm across the two terminals on the sensor, looks like one side is magnetic.

[SWISS]

My bad I thought it was gear driven, looks like it's magnetic. You seem like a fairly sharp guy so I am sure you can figure out if it is the sensor or the pickup on the diff.

[Kramdog]

hehe, my speedometer is starting to act up too. It doesn't have a problem with what temperature it is, but it will work and then quit working for a while. For example, yesterday, it worked for about an hour of the drive and I was doing 85 and hit a pretty good bump and it stopped working, completely. Kinda funny. So, I just need to replace my sending unit I'm pretty sure.

[Ablice]

It's a magentic one, there's a toothed wheel in the diff...

(Give that puppy a smiley face sticker and a quick shot of brake cleaner)

[Kramdog]

Quick SI Board question. I took the cluster apart last night, thinking the batteries were dying. (Here's why I think the batteries were shot) Not all the oil check lights light up when I do a reset, the fuel gauge is a little screwy, the temp gauge won't work till I give the outside plastic a small tap while the engine is running. So, I took it apart and the battery voltages are 3.1 v (each battery is supposed to be 3v.

Could this mean the cluster is bad?

[84318i]

So, what you are saying is it's probably not bad or no way to find out other than replace it ?

Could it be the gear(s) in the diff itself too ?

[84318i]

Quick SI Board question. I took the cluster apart last night, thinking the batteries were dying. (Here's why I think the batteries were shot) Not all the oil check lights light up when I do a reset, the fuel gauge is a little screwy, the temp gauge won't work till I give the outside plastic a small tap while the engine is running. So, I took it apart and the battery voltages are 3.1 v (each battery is supposed to be 3v.

Could this mean the cluster is bad?

You can remove the temp and fuel gauges and clean all the connectors and the rear mounting nut. Your problem seems more like a bad ground or connection since it comes back when you tap the cluster. If not all the lights light up you could check with DMM if the lights are actually good , if they are maybe your SI board is bad since it won't reset all the way.

[Kramdog]

Ok, I will try that. Do you know how the fuel and temp gauges are grounded? I saw an 8mm bolt on the back of the cluster to hold the gauges in. (but it doesn't seem like they connect to a ground) I loosened the bolt and found a washer behind the bolt and then plastic behind the washer.

[84318i]

Kramdog, when you remove the nut that holds the temp and fuel gauge you'll be able to gently remove the gauge from the main cluster board and you'll see the exposed electrical contacts. Your problem much easier

[SWISS]

Kramdog, when you remove the nut that holds the temp and fuel gauge you'll be able to gently remove the gauge from the main cluster board and you'll see the exposed electrical contacts. Your problem much easier

Did you get a new pick up? Can't be that much $ .

[84318i]

I ordered a new diff sensor today from bma, should arrive on wednesday so we'll see if this is it or not...

[SWISS]

I ordered a new diff sensor today from bma, should arrive on wednesday so we'll see if this is it or not...

Best of luck to you. I just got back from Radio Shack with some Ni Cad's for the eta. I know it is the batteries though since it sat for so long.

[Kramdog]

Thanks 84318i, I'm an idiot for not doing that. I took it apart and the ground contacts were black. I sanded them down and she works like a supermodel now.

[SWISS]

Just got done doing the SI's. Replaced with reg old Radio Shack 1.2v Ni Cad's (charged first of course). The OE Varta's had corroded and got under the green film in the bourd so hopefully it is not a lost cause. What struck me as odd though was the back of the cluster said VDO, the front of the cluster said VDO, but the SI board sai Motometer? WTF?!?!