D17 Generator weak???

[Bevan]

Battery is good. Voltage regulator was good, because I replaced it and it does the same thing. Voltmeter works.

Starts great, runs great but when I put the headlights on, the voltmeter shows discharge. I thought it was the voltage regulator but it is not.

Should I take the genny in and get it tested? It was rebuilt about 9 years ago. What else could it be?

 

[DrAllis]

Make a jumper wire and ground the FIELD terminal on the generator with the engine full throttle. If it now charges enough it is a regulator issue or the regulator isn't grounded good. Make da## sure you have a good ground or this test is invalid !!!!

 

[Jim.ME]

Do you have a voltmeter or an ammeter? There is a difference.

An ammeter shows amps of charge or discharge on opposite sides of a center zero. The needle on the discharge side of the zero, on an ammeter, means current is flowing out of the battery. The needle may drop some but should remain at least slightly on the charge side of the zero, if the generator is working when the lights are on.

A voltmeter reads system voltage. It is not uncommon for a voltmeter to drop some when lights are turned on. As long as the voltage stays a volt or so over battery voltage it is not discharging. Discharging would be the voltmeter dropping below battery voltage.

 

[rrlund]

I'll tell you something that happened to me a few months ago on an Oliver 77. The generator always worked, but wouldn't ever charge over about 2 amps. I went to start it on a cold morning and while cranking, it burned the lug in two on the end of the battery cable where it went behind the nut on the starter button. It was the same lug that had the wire to the amp gauge and in turn the coil. When I replaced it and started it up, the amp gauge jumped up to about 8 amps and has charged strong every since. What I'm saying is, you might have a loose or corroded connection that you don't know about, or that's worse than you thought.

 

[Bevan]

Its an Ammeter. The gauge drops to -10 when the lights are turned on. If I cut out one light, its -5 on the Ammeter.

 

[Jim.ME]

(quoted from post at 08:31:30 03/28/22) Its an Ammeter. The gauge drops to -10 when the lights are turned on. If I cut out one light, its -5 on the Ammeter.

Do the test Dr Allis posted.

 

[DrAllis]

Remember, a generator tractor cannot and will not charge with lights on unless the engine is throttle up half-way or more !!!! That is one advantage of an alternator. If you idle the engine down with lights on it WILL DISCHARGE and that is normal.

 

[Tramway Guy]

Is the generator perhaps connected to the wrong side of the ammeter? If so, it could be charging OK, just wont register on the ammeter.

 

[Bevan]

The charge stays the same even when I am at 1600 rpm.

 

[DrAllis]

If you have the field terminal on the generator absolutely grounded and you say a good voltage regulator, and the engine speed is 1600 RPM, then the generator or it's wiring must be the issue.

 

[Bevan]

Did your test and no change in ammeter
with the engine at 1600 and F terminal
grounded off engine or battery. Tried to
ground new voltage regulator directly. No
change either.

 

[Bevan]

Thanks Dr. Allis,

So I had the Generator tested at the local shop. It passed with flying colors. Put the genny back on, tested the connections, and put it back together with the intention of
running bypasses of the electrical loom to check for faults. Didn't end up needing to. Kicked the engine on and it worked correctly. Head scratcher to what I fixed.

 

[DrAllis]

There are a couple of things that are very normal with your generator charging system. #1. If you start the engine at low idle, you will notice no charge whatsoever until you throttle up to say 800 to 1200 RPM, when the regulator locks in. #2. Whenever you idle the engine clear down, there is a point the ammeter needle will dip into the discharge area and then return to zero. This is normal, as the points in the regulator just opened disconnecting the gen from the circuit. #3. When using the lights, the generator cannot keep up to the demand until probably over 1,000 RPM and this is very normal. Why did we go to alternators ??? Because the performance is so much better at slower engine speeds.

 

[jimtrs]

(quoted from post at 07:49:54 04/04/22) Thanks Dr. Allis,

So I had the Generator tested at the local shop. It passed with flying colors. Put the genny back on ..... ...... and it worked correctly. Head scratcher to what I fixed.

Probably got better grounding from R&R.

Always bring your regulator with the generator when bringing in for testing.