Generator cut out

A

aermotor

Well-known member
I don't know if my cut out is diode or not. It is a New Rex. I have amp charge change by moving the 3rd brush and a couple amps with the lights on. I am on the bottom of the scale with electrical knowledge. How can I test with a trouble light - battery goes dead after a couple days - 5 years old.
 
If the battery dies like you mention then check for a draw and fix it.

Remove battery grd cable and insert volt meter/test light between battery post and cable end. If there is voltage then keep disconnecting stuff until light goes out and that'll be the draw/problem.
 
aermotor said:
I don't know if my cut out is diode or not. It is a New Rex. I have amp charge change by moving the 3rd brush and a couple amps with the lights on. I am on the bottom of the scale with electrical knowledge. How can I test with a trouble light - battery goes dead after a couple days - 5 years old.
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Battery! Take to auto store they can do a load test on it!
 
Patrick L. said:
If the battery dies like you mention then check for a draw and fix it.

Remove battery grd cable and insert volt meter/test light between battery post and cable end. If there is voltage then keep disconnecting stuff until light goes out and that'll be the draw/problem.
Click to expand...

No, this will destroy a voltmeter. An ammeter would be connected this way, not a voltmeter.
 
ndnchf said:
No, this will destroy a voltmeter. An ammeter would be connected this way, not a voltmeter.
Click to expand...

MMM, no, It won't destroy a voltmeter. However using a voltmeter instead of an ammeter will give you no indication of the amount of drain.
 
I did find a bad battery mentioned on my OP. Next question I have, the third brush is set to 3 amps with the lights on and 8 to 9 with lights off. I do plan to be doing all my driving with the lights on. Is this too high or should I move down a bit?
 
Amp reading doesn't tell you a lot, really. Best set to around 7 Volts at the battery terminals, fast idle, with lights on if you drive it that way all the time. 8 to 9 A is too high in any case.
 
A few comments:

Multimeters have a fuse in the amperage reading circuit. Depending on the make it could be 10 amps. If you have a short and use the amperage reading it will blow the fuse. Also, depending on the multimeter, measuring voltage will not kill it unless it is a old manual one and you set it on millivolts instead of 10 volts.

I recommend installing a voltmeter in your car in addition to the ammeter. It will tell you the condition of the battery before you start the car and if the voltage falls too much when starting due to a bad battery or bad starter or other electrical problem. It will also tell you if you are undercharging or overcharging the battery. The charging voltage should be 7.2 volts.
 
eagle said:
MMM, no, It won't destroy a voltmeter. However using a voltmeter instead of an ammeter will give you no indication of the amount of drain.
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I'm not going to argue the point. But remember he said "Remove battery grd cable and insert volt meter/test light between battery post and cable end". This would put the volt meter in series and allow all the current to flow through it. A Voltmeter should be connected in parallel, an ammeter connected in series.

This short video explains how the two meters should be connected and why:

https://youtu.be/kADwx06TZxk
 
Ideal voltmeters have infinite resistance, and hence you can safely measure an open circuit like described above. How you employ a voltmeter depends on what you want to measure - put parallel it measures voltage drop across whatever its put in parallel with.

Ideal ammeters have zero resistance - they short out between the terminals - and should be put in series in the circuit you want to measure amperage in.

\Dk
 
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