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Speedo pulse generator diagnosis with analog VOM 700 1992

posted by  someone claiming to be io333 on  Mon Mar 29 05:08 CST 2004 [RELATED]

As I delve ever deeper into the inner workings of the Yazaki...


I have my speedo disassembled, and note first of all, that the magnetic pulse *is* modified before it is fed back off to the cruise control. Just for anyone that digs this out of the archives in the future.

Here is my question:

I notice that the wires that make the speedometer go are four:

1. 12v
2. Ground
3. S+
4. S-


I know what 1 and 2 are. They seem fine.

I assume that S+ and S- are coming from the rear end pulse generator.

I have an old (15+ years) analog RadioShack VOM. It has two ammeter settings:

250m
25u(250mV)


I'm guessing that is 250 miliamps and 25 microamps max measurable at 250 milivolts (or about .07 watts max).

Can I just stick the VOM on one of those settings, connect the leads red to S+ and black to S- and see if I get something out of the generator as I drive down the road? Can this hurt the sensor? Which setting? 250m or 25u





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