Btw, the speedo, the odometer, and the tripometer all die together -- that is consistent. I read the archives where Art Benstein said that is a clue to look to the rear.


Art Benstein doesn't know diddly do about 7/9 speedometers.

One tip I can offer regards your use of the ohmmeter to qualify the sender. Please save yourself a lot of potential grief by checking your meter against a known resistance in the ballpark with the value you are measuring, e.g. get a 1500 ohm resistor and be sure your meter reads near 1500 ohms.

Though I have not tried it on a 7/9 car, I expect the same 240 trick of substituting a small AC voltage from a wall transformer, say 5-12V, for the differential sender, will make testing and isolating the problem easier with no scope.

Success at replacing capacitors and cleaning up electrolyte damage may depend on experience repairing printed circuit boards. I don't know the situation with the 700 cars.
--
Art Benstein near Baltimore

My wife has a slight impediment in her speech. Every now and then she stops to breathe. - Jimmy Durante