Spot Rot

Problem: hot start issue has come up: solenoid won't engage after heat sinks in.

AGM Battery open voltage seemed low (12.45) and charging voltage also seemed low: 13.3 with blower, headlights etc on at 1500-2000.

So I tested the diode trio and the rectifier.

With a good quality meter, all read infinity in one direction and about 5k ohms in the other.

5k ohms seems way too high, but all are the same and the alternator was charging.

Any thoughts?

zuendler

Diodes cant be measured with an ohm-meter in the way you think, they don´t have a constant resistance in the passing direction.
At normal diode you will meassure a voltage drop of 0,7V when a current is going trough it. You can hook a light bulb on it just to test it. If the current goes trough in one direction, and not in the other direction your diode is alright. You donßt need to measure the voltage drop.
A broken diode lets go the current in both directions and a fully burned diode usually shows an open circuit.

Spot Rot

Thanks.

It seemed that the measured resistance was not accurate.

I took your advice.

I hooked up a 3V battery with a LED and it lit one direction and not the other on all the diodes - obviously wouldn't if the diode resistance was the measured 5k ohms.

Richard454

A better test- take the meter switch it to AC. Measure the voltage at the alternator-where as at the battery won't be as accurate. Anything more than .5v means= you might have a problem.

Richard

Richard454

A better test- take the meter switch it to AC. Measure the voltage at the alternator-where as at the battery won't be as accurate- car running w/ a load-lights- fan on it at 1500RPM. Anything more than .5v means you might have a problem.

Richard