Testing Resistance

[Tools]

I am having some issues with my van (1984 Hiace) and the alternator is overcharging. The alternator itself has been replaced but the issue persists. It has an external regulator which I have removed and tested in accordance with the manual. It would appear that it is shot but I want to confirm that I a testing it correctly.

I have a couple of multi meters and the only thing I ever use the resistance function for is for buzzing out cables and testing continuity. The dial has seven settings for Ohms but I am not sure which one I should be starting on. The dial is labelled 200,2k,20k,200k,2000k,20m and 2000m. The manual says for one pair of wires for instance that their should be an infinite reading and then if the contacts are closed it should be 100 ohms. In this instance should I be starting on the 200 range? What if I don't know what reading to expect, then what would I start on? If there is an infinite reading, does that mean it is open circuit?

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[Tools]

The regulator has two coils in it. One is nice and copper coloured, the other has some small areas that have lost the copper colour and are more silver. Could this be indicative that the coil is shot?

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[Tools]

If I check for continuity on each coil, the copper coloured one buzzws out, the one that has lost some colour doesn't. Is this a reliable approach to testing the coil?

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[Bohdan]

It doesn't matter what scale you start on. Place the probes on the coil and adjust the scale until the reading is near the middle of the scale to get the most accurate reading. A reading of infinity is an open circuit and for a coil means it's dead. Any other reading could be affected by poor contacts, shorted turns or some other fault so you need to know what it should be before you can declare it as good.

[Tools]

Thanks Bohdan. It seems that my voltage regulator is shagged so I have ordered a new one to pick up tomorrow.

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[Tools]

Slipped the new regulator in this afternoon and the charge light has now gone out. Need to check the voltage tomorrow but I suspect all is now good. The new regulator is one of those fancy new fangled solid state electronic bits of kit, nothing like the old points type that it has replaced...

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[Tools]

13.9 - 14.0V at the battery terminals :2tsup:. Case closed !

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