Any tips on trouble-shooting generators??

[jiffy]

so, I think the '64 Mustangs had generators, and my 63.5 Galaxie has one,

I think the battery is not being charged, but I haven't got clear evidence so hoping there is some experienced heads here who can offer testing and proving steps for me.

Battery is around 12.9v at rest, car started ok if a little lethargic (hadn't been started for a week or two).

Drove it around a little - not far, maybe 10 minute trips, 4 times. Started ok but still not as enthusiastically as normal.

There is a GEN light when the ignition key is turned, but it goes out when the engine starts.

Battery measures 12.8v before and after starting at idle, revving to 2-3K rpms makes no difference - voltage is still 12.8v

Any free wisdom floating around? Car hasn't left me stranded yet, but would prefer it doesn't either....

Thanks in advance

[fredm666]

I believe most of the cars with generator have been changed to alternator, but in mine I still have a generator.
If car is sitting in the garage for too many days in a row I normally disconnect the battery, because over time the battery charge tends to go down. When driving I noticed the generator is not recharging the battery as quick as an alternator; not a problem if it is a decent drive, it might be not charging enough during short trips.
Anyway I bought a battery charger from Supercheap Auto, it works well to keep the battery charged when required

[GEOFF289]

I don't pretend to know but a couple of things come to mind.

1. Does the Gal have an ammeter like an early Mustang? if so, does it go to the positive side when the engine is running? That would indicate it was charging the battery.

2. I don't think a generator will do much at idle so voltage remaining the same as the engine off state at idle should be expected, but it should rise when rpm goes up to the 2-3K you mention.

3. What happens when you apply a load like turning the lights on. I think voltage should initially drop and then recover. If it doesn't recover I'd think the gen was possibly suspect.

4. 12.8 volts with engine off is pretty healthy but your battery could still be marginal in terms of maintaining cranking amps. Supercheap will test the battery for you and give you a printout.

I repeat my introductory caveat.

[jiffy]

Good points Geoff - I'll check with the lights on.

It's been ok in the past, I have a battery tender on there now so I'll compare it afterwards - I might hook up the DVM so I can measure the voltage as I drive.

It's going to get an engine swap soon, and I have a few original Ford alternators, I might hook them up instead - is there a wiring diagram that anyone has that details how to do that Gen-Alt swap?

[GEOFF289]

This might help. It's specific to Mustangs but I'd be surprised if the Gal was different. Looks like you need a different voltage regulator too.

https://www.vintage-mustang.com/attachments/64vs65-generator-diagram-jpg.646090/

[pmb0186]

basically a generator will do little charging at idle, an alternator is always charging hence superior.
If you are still only get 12.8v off idle that's your problem.
Could be three things generator, voltage reg or wiring.
At the back of your generator there will be 3 wires, ground, field and armature.
Measure with a voltmeter approximate 12v on Field wire (small gauge) when ignition turned on and Ov when off.
Start car you should measure greater than 13V on field wire (larger gauge) wire depending on load/engine speed.
All measurements in reference to ground.
Check generator ground to engine chassis and battery.
If above okay likely voltage reg/wiring.
 A further conversation

[jiffy]

Thanks Pete - I will have a look - good info.

Great diagram Geoff....

[GEOFF289]

In the creepy way of the internet this popped up for me and might be of use to you Jeff.

https://www.youtube.com/watch?v=gpGsjyJ9gCo&t=52s

Seems to be using the same wiring diagram I posted earlier

[jiffy]

Good video - after watching a few, I might try thumping the regulator box as a first step!