E30 M3 Faulty speedo HELP!

[busterm3e30]

I have a late 1989 2.3 E30 M3 UK spec, the speedo have just began to work intermittently some times it will work correctly, others it will flicker or just not work at all. Any hints or tips to help fix it would be greatly appreciated.

[Barx325i]

the diff sender cable will most likely be the cause.. it perishes & fails intermittently as you describe

[busterm3e30]

the diff sender cable will most likely be the cause.. it perishes & fails intermittently as you describe

sorry i forgot to mention in the original post that he diff sensor has been replaced with a new one, and other ideas?

[jmc330i]

It's the cable to the sensor that usually causes the problems, rather than the sensor itself. You need to replace about 30cm of the wire from the plug back. The plug is the same as a headlight plug, so you could find one of those with a long enough length of wire.

Does the trip meter etc still work when the needle doesnt? If it does, the sensor or wiring is most likely not at fault (as with mine).....

http://www.e30zone.net/modules.php?name ... highlight=

I've not looked into mine yet, need some time to take the cluster out etc.

[maggspower]

the diff sender cable will most likely be the cause.. it perishes & fails intermittently as you describe

sorry i forgot to mention in the original post that he diff sensor has been replaced with a new one, and other ideas?

Yes but it is the WIRES that can break down and cause your symptoms.

[busterm3e30]

When the Speedo stops the odo and the trip stop working as well, if to tap the speedo when moving it does flicker which is making me thing that its a connection behind the cluster. Any advice on taking the cluster out?

[Barx325i]

the odo & trip use the diff pulse to work which explains the total loss - if you've replaced the sensor, any disturbance back there can easily bugger a half buggered wire

[busterm3e30]

the odo & trip use the diff pulse to work which explains the total loss - if you've replaced the sensor, any disturbance back there can easily bugger a half buggered wire

What section of wire will need replacing? where is the next connection from the diff?

[Barx325i]

As Jim says. about 30cm would do, plus the join will be hidden from view. It's usually the end close to the connector which fails

[busterm3e30]

As Jim says. about 30cm would do, plus the join will be hidden from view. It's usually the end close to the connector which fails

Cheers will have a look at that, do you think its worth taking the instrument cluster out and checking the connections behind there as well?

[Barx325i]

it's almost definitely the cables, but can't do any harm I guess. We could be sending you on a wild goose chase with the cables after all.

[Brianmoooore]

Cheers will have a look at that, do you think its worth taking the instrument cluster out and checking the connections behind there as well?

Definitely not. E30s do not suffer from 'poor connections', except in a very few places and for well documented reasons.
The copper in the wire of the final length of loom to the diff. is affected by the vibration from the diff., changes its crystalline structure, becomes brittle, and fails. Replace the wire and plug - if you repair it, it will fail again.

[Barx325i]

I repaired an anchor winch on a boat this summer, I cut back about 12" of copper wire, which had fully oxidised, just a pile of green powder all over the newly upholstered cabin, but at least the anchor worked..

[pacerpete]

I repaired an anchor winch on a boat this summer, I cut back about 12" of copper wire, which had fully oxidised, just a pile of green powder all over the newly upholstered cabin, but at least the anchor worked..

Ah, that explains the recent paypal digs between Rav and yourself

[Barx325i]

[busterm3e30]

Cheers will have a look at that, do you think its worth taking the instrument cluster out and checking the connections behind there as well?

Definitely not. E30s do not suffer from 'poor connections', except in a very few places and for well documented reasons.
The copper in the wire of the final length of loom to the diff. is affected by the vibration from the diff., changes its crystalline structure, becomes brittle, and fails. Replace the wire and plug - if you repair it, it will fail again.

Ok But if its not a connection behind the cluster is good then why does the speedo try to move if you tap the speedo when moving, Ive checked the diff sensor and wiring all looks ok no signs of perishing or anything. Im going to get a multimeter tomorrow and check it properly before I start replacing wires if that is needed

[Barx325i]

I think you may have answered your own question there but if reseating the cluster plug doesn't solve it, it could well be a cluster/dial fault..

[busterm3e30]

I think you may have answered your own question there but if reseating the cluster plug doesn't solve it, it could well be a cluster/dial fault..

Ive taken the cluster out have it infront of me now going to reconnect and go for a run see what happens,

[Barx325i]

have a look at the pins, while it's out JIC there may be a build up of clag etc..

[Brianmoooore]

If the speedo responds to tapping the instrument cluster, remove all the cross head screws on the back and split the front and back halves. Unscrew the screws on the back that secure the speedo, and pull it out from the back half, then carefully check the solder joints of the pins that connect between the speedo daughter board and the main circuit board, and resolder as necessary.
While you have the cluster apart and the soldering iron out, inspect two solder joints close to the temperature gauge that correspond to a raised rectangular box on the back of the cluster case. If they haven't received attention yet, they will almost certainly be badly deteriorated.

[e30-EVN]

i have this fault and i can confirm on my car it is the speedo sensor plug on the dif.
the plug has fallen appart and the round female connectors inside the plug have stretched thus making a bad connection... also there is a join so far up tapped up so obviously shes had a new one before. i guess this is a very common item to fail. the plug itself has broken up and wont clip into the diff plug so it doesnt stay in and if going over bumps in the road the speedo dances up and down

ringing sytner in the morning to order an new one

[busterm3e30]

Ive got a new diff sensor coming and im putting a new section of wire in from the diff through the rear bulkhead hopefully that will do the trick, the car is in pieces at the moment not pretty