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Electrical System Troubleshooting

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Chad

08-22-2003 06:50:19




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I posted a message a couple of days ago about electrical system charging troubles on my SMTA. Well, last night I was going through the generator/regulator troubleshooting flowchart that Bob M has put together (very helpful) with some interesting results that I was hoping someone could help interpret.

1. With the engine and electrical switch off, the ammeter needle is just below "neutral" (no charge or discharge) in the discharge area of the meter. Is the needle supposed to read straight up at "neutral" when the switch is off? (in other words, could there be a calibration issue with the meter or does it really matter?).

When the switch is turned on, the needle drops further into the discharge (can I assume the ammeter is OK?). 2. I ran a ground jumper from the regulator base to ground. No charge.

3. This is the interesting part. When I jumpered between "BAT" and "GEN" terminals at regulator, the ammeter needle shot deep into the DISCHARGE realm, not charge. When I disconnected the jumper, the needle returned to the previous discharge level. Does this indicate a bad regulator? I'll probably go ahead and replace this per advice from a previous post, but I was curious as to why it would drop into discharge like that.

4. While I had the multimeter out, I decided to check voltages between different points in the system. I noticed while the engine was running, there was approximately 5.8 volts between the F terminal on the generator and the L terminal on the regulator. When I increased RPM, the volts dropped to 5.2. With the engine off and switch on, the voltage is negligible. Would this indicate that the generator is working?

Thanks a bunch for any input or advice and I apologize for my lack of know-how and experience.

Chad

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Bob M

08-22-2003 08:17:16




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 Re: Electrical System Troubleshooting in reply to Chad, 08-22-2003 06:50:19  
Hey Chad - To your question #1, the ammeter "parking" a bit to the left of 0 while at rest is a calibration issue. You could replace the ammeter if it bothers you. But so long as you know all readings are offset a bit it's not a big deal.

To questions #2 and #3, the ammeter indicating deep discharge when the regulator BAT and GEN are jumpered says the generator is not working (also incidentally that the problem is related to the field windings and/or the 3rd brush - not the armature windings/main brushes). However just to be sure, try repolarizing the generator again (momentarily jumper the BAT and GEN terminals with the engine off), then test the system once more.

To question #4, you should take voltage readings directly across the battery terminals. If the generator is charging you should see 7.0 volts or a bit more. Anything less than about 6.4 says the generator is not working.

Hope this helps!

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Chad

08-22-2003 08:49:51




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 Re: Re: Electrical System Troubleshooting in reply to Bob M, 08-22-2003 08:17:16  
Thanks Bob!

This helps tremendously.

Chad



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