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

[Jean]

Ok, this one is getting on my nerves now. I've gone through 3 clusters, couple si boards and even bypassed the si board. Here is what's happening-

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

Only thing left is to pull the speedo/odo from the 90 325i cluster and i'll instal it in my 318 cluster and try it again.

[Jean]

I just looked at the 90 325i speed/odometer and it's different from my 318i speed/odometer. One has 4 pins next the odometer gears and 325i odometer has 5.

[AlpineIS]

Clearly your problem is not anywhere related to the cluster. And if I remember correctly the SI board has no interaction with the the speedometer/odo. The SI board regulates the tach (almost sure of this).

Your problem is most likely at the speed sensor, where the signal is acquired. I would bet either the wires are frayed or the sensor is dirty/bad. It is located on the differential, right aboive the fill hole.

Inspect it and report back.

[Jean]

Plug/ wires look ok. Measured across the sensor terminals, shows 8ohms.

[porsche gt1]

Clearly your problem is not anywhere related to the cluster. And if I remember correctly the SI board has no interaction with the the speedometer/odo. The SI board regulates the tach (almost sure of this).

Your problem is most likely at the speed sensor, where the signal is acquired. I would bet either the wires are frayed or the sensor is dirty/bad. It is located on the differential, right aboive the fill hole.

Inspect it and report back.

X2 stop replacing your boards, sell them on ebay or something.

[Jean]

I know, but I couldn't be sure it wasn't an SI board until now. Now I gotta replace diff speed sensor and hope it will fix it and have a 90 325i mint cluster that i'll have to sell .... argh

[mtechnik]

I had and still have the speedometer problem u have but it would work again when it feels like.

I changed the sensor once with a used on cause we were testing. My mechanic also examined the wire/harness thing from the outside of the car and found no breaks in the wire.

In my case there could be a break along the interior. I would advise you also check this !

[Mike325]

I had and still have the speedometer problem u have but it would work again when it feels like.

I changed the sensor once with a used on cause we were testing. My mechanic also examined the wire/harness thing from the outside of the car and found no breaks in the wire.

In my case there could be a break along the interior. I would advise you also check this !

Thats what I was thinking.

[Jean]

Well, I ordered a new diff sensor today from bma, so if this doesn't solve it then i'll start tracing the wires.

[Jean]

Problem solved, was a bad connection at the speed sensor. :p

[mtechnik]

YAY !!!! solved