Speedo problem, help!

[M325ix]

Hi, I own a 86 325ix. My speedo doesn't work. I read that maybe the SI board causes the problem so I purchased another cluster from a 90 325ix. Didn't fix the problem. So next I replaced the rear diff sensor. Also didn't fix the problem.

I purchased the car without it working. The first month I had the car it worked 1 time the whole night, but once I shut the ignition off that time, it hasn't worked since. The old cluster had new lithium battery board in it and it held its memory, but the fuel consumption needle only worked for a few minutes after unplugging and replugging the cluster in. The new cluster also is a lith. battery cluster, holds its memory, and was known to be working. With the new cluster the consumption gauge bounces back and forth all the time but I'm guessing cant get a correct reading since it doesn't know how fast its going. Is there something else along the system that might be dead? Does anyone have a electrical diagram of how it runs?

Everything else on the cluster works perfect except the speed. Also I'm not sure if this has something to do with it, but when I do the reset procedure for the board, only the inspection light shut off, but the oil service stays on???

[nando]

how about the wires from the diff to the speedo? they often break right at the diff plug.

[M325ix]

how about the wires from the diff to the speedo? they often break right at the diff plug.

I looked them over but they seemed fine, unless there is a break somewhere farther up. How does it run through the car?

[nando]

it pretty much goes straight from the diff to the back of the cluster

[M325ix]

the previous owner changed the dash over, maybe he damaged the wires somewhere, anyone know how they run through the car?

[browntown]

speedo problem?

[durtyE30]

I'm having very similar issues, and my plan is to replace the Speedometer Impulse Sender, which attaches to the back of the differential. It is easily replaced, and barring an issues with itself or the cluster (which you've already ruled out), would be the next step, besides double checking your wiring as others have suggested.

Test the leads at the impulse sender with a multimeter for continuity, just in case, but it's most likely that sender.

It's like $20 on Pelican/FCP/Favorite parts warehouse.

Part #: 62-16-8-357-020-M375 is what you need for your car. Don't forget to get a new O-ring for it too. And it is actually $29.50 on Pelican, I found mine cheaper elsewhere. I'll let you know if it fixes my issue when I get around to changing it, but everything leads to saying it should. 20+ year old parts after all, probably still the original one.

[M325ix]

I'm having very similar issues, and my plan is to replace the Speedometer Impulse Sender, which attaches to the back of the differential. It is easily replaced, and barring an issues with itself or the cluster (which you've already ruled out), would be the next step, besides double checking your wiring as others have suggested.

Test the leads at the impulse sender with a multimeter for continuity, just in case, but it's most likely that sender.

It's like $20 on Pelican/FCP/Favorite parts warehouse.

Part #: 62-16-8-357-020-M375 is what you need for your car. Don't forget to get a new O-ring for it too. And it is actually $29.50 on Pelican, I found mine cheaper elsewhere. I'll let you know if it fixes my issue when I get around to changing it, but everything leads to saying it should. 20+ year old parts after all, probably still the original one.

yeah thats the part i replaced today and no luck. I will start testing the wires tomorrow.

[jlevie]

To check the wiring, disconnect the speed sensor at the differential and at the cluster. Check the resistance of the wire, which should be less than an ohm. Then check to see if the wire is grounded, which should show infinite resistance.

[M325ix]

Problem solved, I somehow burnt out the 7.5 amp fuse while changing the sensor. Works great now!

Thank you for the help everyone

[pizzaboy69]

Problem solved, I somehow burnt out the 7.5 amp fuse while changing the sensor. Works great now!

Thank you for the help everyone

hey bro, i have the same problem, ive done everything you did except check the fuse. sorry for being a noob but where is this 7.5 amp fuse located? what number in the fusebox? thanksin advance!

[boosted_E30]

hey bro, i have the same problem, ive done everything you did except check the fuse. sorry for being a noob but where is this 7.5 amp fuse located? what number in the fusebox? thanksin advance!

#12 fuse under the hood.

[pizzaboy69]

thank you kind sir!

[davem]

how about the wires from the diff to the speedo? they often break right at the diff plug.

This has happened to my car, one of the two wires is cut, and by the looks of it the second one doesn't have much life in it (these wires are as thin as fishing line?!). How does one fix this? Is there a part number for the pig tail?

[Simon S]

This has happened to my car, one of the two wires is cut, and by the looks of it the second one doesn't have much life in it (these wires are as thin as fishing line?!). How does one fix this? Is there a part number for the pig tail?

fwiw - (I had same deal) and clipped a 'pig tail' from a yard car and spliced it in.

Had trouble trying to pin down a pt# also. Advise to send a request message to a parts guru like blunt..