speedo testing

[jernest]

I was having some problems with my speedometer(1985 325es) intermittent failure, I would hit the dashboard and it would resume working for a while. I read that the solder joints sometime came loose, so I took it out and re-flowed the connections. When I put it back in it quit working alltogether. After months of deliberation I decided to go get one from a used parts dealer. I put the newly purchased speedo in today, only to find it not working. Does anyone have any idea what I can test for to see if the differential sensor is failing, or the wireing is bad? Can I check for voltage/resistance on the insrument cluster wires while moving? Any suggestions appriciated.
Thanks

[Wayne 962]

Hi there. Good question. I'm not sure of any sure-fire way to test the sender. I believe it works like a hall-effect sensor, similar to the crankshaft sensor and the camshaft sensors.

You could probably remove the sensor from the differntial and take a look at it. If there's something catastrophicaly wrong with it, the failure mode might be obvious...

On the other hand, the sender is only $30:

http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search.cgi?command=show_part_page&please_wait=N&make=BMW&model=BE30&section=TRANSM&page=4&bookmark=19&part_number=62-16-8-355-008-M375

-Wayne