Potentially unusual Speedo issue

[beemerbird]

1988 325i Touring, 58K

Sometimes the speedo works fine.

Sometimes the speedo doesn't work until the car is at temperature.

Sometimes the speedo drops in and out from reading correctly.

Sometimes the speedo reads a steady, random, speed which doesn't really relate to the progress being made (I found myself doing 42 in a 30 today as I was checking the speedo not the sat nav). It does tend to always read low when it does this.

Any advice gratefully appreciated.

Fi

[beemerbird]

[Brianmoooore]

90% of speedo faults are associated with fractured wires to the plug of the diff. sensor, and most of the other 10% are down to cracked solder joints around the pins that plug the speedo itself into the main cluster circuit board.

[mattycoops43]

LOL "potentially unusual"-but sadly not!

[beemerbird]

Well, I was hoping that the symptoms I had described would indicate the likelihood of it either being at the diff OR at the clocks. My previous E30 had speedo problems which were obviously diff related and cured by sorting out in that area. The behaviour of the speedo in my current E30 is entirely different, so hoped that someone might recognise the symptoms as potentially clock related.

The car has been displaying these symptoms for over a month now, and my guess would have been that diff wiring would have given up completely during a months use

I was just hoping that someone could confirm or otherwise

[Brianmoooore]

Thump the dash while you're driving.

[beemerbird]

Will try that next. I see your thinking here. Thanks, Brian.

[beemerbird]

Tried thumping both the top of the dash and the face of the clocks today whilst driving. Made the needle jump from it's dead potision. Back to the dead position. Then, next time I glanced at them, they were working again, but reading low. Towards the end of my excursion in the car they were working fine

[Brianmoooore]

IIRC, you know how to use a soldering iron, so dig the speedo out of the cluster, and do a bit of a reflow on the circuit board.

[beemerbird]

Thanks for the advice. Indeed I am very familiar with soldering irons. I just didn't want to start trying to sort it out at the diff if it was more likely to be at the clock end, and vice versa. I shall report back

[Alyman]

Could you post up some pics as you go along with the process? I think I might need to buy a soldering iron...

[beemerbird]

I will - no problem.

[KSP_E30]

If the wire on the back of the diff is the issue....
B61130007441 is replacement wire with connector from BMW .