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Generator not working, took apart, what's next?

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BrandonBJ8

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After killing 2 batteries, I knew my generator had some issues. I tested it and at around 1000rpms, it was getting around 4-6volts with a couple random quick spikes 10-20. I've taken the generator apart and am not exactly sure what I need to do next. Everything "looks" okay to me, but this is my first time taking apart a generator. I've attached 2 pictures, would be great to get some advice on what to test and how to test it to determine what I need to do to get it working. (Plan to do alternator in the future, but want to get this working for now.)

Thanks!
 

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Did you lubricated it as part of the routine maintenance? The brushes look good. Did you check the fan belt for to too tight or too loose? Regulator points OK? I'd would have clean all electrical connections and coat with dielectric grease before taking the generator apart. Did the armature spin easily? Of course, now would be a good time to switch to an alternator if you have that inclination. Or put it back together and bring it to a shop that can test it. I would guess it is not the generator. They tend to free or burn. But that is only a guess.
 
The most likely issue is sticking brushes since there is no sign of any stress. I'd clean the brush holders, make sure they slide in and out easily and reassemble and test. I reckon it'll be okay.

Ash
 
Did you check the voltage regulator? As you're seeing dips and spikes that's more likely the culprit. The VR regulates the current going to the generator field coil to regulate the generator output which fluctuates with rpm.

It also cuts the generator out of the charging circuit when the voltage of the generator is lower than battery voltage to avoid draining the battery. From the pics your generator looks reasonably clean. As it's open check the brushes length, the bushes/bearings and you can clean up the commutator.

Next to the shop manual there are a number of good online resources for generator and Voltage regulator.

For instance, I used the setup as described in article et-121 at

https://mgaguru.com/mgtech/electric/electr_1.htm

to bench test my voltage regulator

Bert
 
I put everything back together and decided to test again. The car started up fine and ran for about 20 seconds. The battery dropped from 12.6 to 12.4 and then creeped back up to 12.6 and towards 12.7. Then the car just died. I tried starting it and it wouldn't turn over at all. Any ideas? I thought I may have mixed up the wires when reconnecting the coil, but the car started fine initially.
 
Or the battery cable connections?
 
The car is trying to start, but it just keeps cranking so it's getting power, just not turning over.
 
The generator hasn't anything to do with starting the car. If the starter is cranking that's good. I'd start by tightening the voltage regulater connections on the dash. I'd also check the wiring to the distributor as you may have broken the ignition wire coming from the distributor. Also check the rotor inside the distributor. See if you're getting spark to the plug wires.
 
Johnnys right the car will run without a generator so you have two different problems. You make no mention of cleaning the armature with fine sandpaper or testing continuity at various points inside the generator. They aren't complicated but you do need specific testing equipment to be sure . The armature could have a short internally or the field coils could be shorted or broken. You should be able to find someone in your area that can do this for you. Where are you testing for generator output? On the generator or at the battery? The voltage regulators are equally problematic. Kevin
 
Johnny - All the connections look good. What's the best way to check the rotor to see if I'm getting a spark?
 
tahoe healey said:
Switch with a new one.
Click to expand...

... or pull a plug wire and hold the end close to the block whilst cranking the engine. Use insulated pliers, gloves and/or wrap the wire with a rag lest you get zapped.
 
Crank the engine over with the cap off and the key on. You should see a strong blue spark at the points as they open and close.
 
If the engine spins and when you take out a spark plug leaving it connected to the wire but rest it on the engine block so it is grounded and you see a spark then next easy check is fuel, take off the top of the float chambers and check that they have fuel.
Jay, '65 3000
 
The only way to check the rotor is to exchange it with one that you know does work. There was a rash of bad ones out their recently. If you haven't replaced it yet buy a "premium" one from Moss. Btw, you can test the spark coming from the coil, through the rotor to the wire leading to the spark plug by removing the wire from the plug and by placing a metal screwdriver from the spark plug and holding it close to the spark plug wire, you shoud see a nice blue spark jump from the wire to the screwdriver.
 
I did the test with a spark plug wire and screwdriver and got no spark. With the key turned on, I checked voltage at the coil and got no reading. I then checked the white wire going to the coil and it was getting 12 volts with the car on. So it seems like its the coil.

How can I test my coil or check to see if it's bad? Anything else to check?
 
You'll get 12v coming out of the coil when the points open and close therefore check your points gap. If your condensor and coil are ok you will see a strong blue spark and hear a snap at the points as they open and close. Weak spark? Change the points and condensor. Then suspect the coil, best checked by substitution.
 
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