weird charging problems

Giles

Giles

Junior Member
I'd be very grateful for some advice. No charge is registering on my ammeter. I have checked the following: 1) the ammeter - works ok in both directions. 2) cutout (old-style magnetic, not diode, but purchased recently):it closes when 6v DC is put through. Its gap is correct. 3) all earthing points for lights, indicators, battery and my extra engine-to-chassis strap). The genny (powerhouse) spins happily when 6v is put through it but I know this does not necessarily mean it will also charge, so - and this is where it gets interesting - I put my reserve genny - an almost unused reconditioned 3-brush unit - into the car and that won't charge either. Before I call out an expensive electrics man, what else should I try? Spring weather has finally hit Britain, I'm booked for lots of runs, and I'm at my wit's end!
 
Make sure you polarize the generator just in case it has lost the residual magnetism.
Make sure the terminals at the firewall are CLEAN and TIGHT.
If you have the original metal tube for the wire running from the cutout to the firewall, make sure the wire isn't touching ground somewhere inside the tube.
Have you looked at the rear of the ammeter to be sure the terminals are tight, as well as the two special slotted round nuts on the meter itself?
 
The fact that the cutout closes at 6 volts is a good start, but now you have to make sure the contacts are conducting. Have you cleaned them? As Mitch said, put a volt meter on the output terminal of the cutout before and after starting the engine. You should show battery voltage before, and at least a half volt more when the generator is running.

BTW, if the contacts don't conduct the generator output to the battery, then the charging system basically has an open and the generator can put out up to 40 volts and cook itself.
 
Also make sure the generator itself is grounded to where it is mounted. And any where else the end plates to the tube of the generator. Good grounds are very important.
 
To polarize the generator just use a short wire (or pliers) to jump the 2 terminals on the cutout. You should see a small spark, and if the belt happens to be off the generator should spin in it's normal direction of rotation. As Patrick said, one second is enough.
 
Giles,

With the car running, what is the voltage at the starter terminal ? Is it higher than the same value with the car not running ? If so, charging is working.

Marc
 
Thanks for your further suggestions. I've polarised the generator (spins well), checked and cleaned earths, checked voltage with engine running and not (it's the same), and even renewed cutout, ammeter and battery, just in case. Still no charge - and also, oddly, no load when I use the starter or run the engine, although load when I switch the lights on shows as normal. Rather than test your patience further, I'm handing the problem over to a car electrics specialist. I hate giving up on a puzzle!
 
did you verify that the wiring is still correctly hooked up? You've done a lot of changes, perhaps you fixed the initial problem but created another?

Do you have the wiring diagrams?

rob
 
Starter load will not show on the ampmeter. Silly question but you do know it will not charge at ldle, right? Try it at 1500-2000 rpm's.
 
If the ammeter shows a discharge when the lights are on, that seems to be alright.
That fact that the generator spins when powered is a pretty good indication that the generator is OK. [mostly]
With the engine running and you jump across the two cutout terminals[ flashing/polarizing] it should properly remagnetize the innerds of the generator.
If no charge is showing at a fast idle, then I'd think either the third[movable] brush needs adjusting or the cutout is defective or needs cleaning/adjusting.
 
At fast idle did you check the voltage at the generator output terminal?

I would make sure the field and output wires didn't get mixed up on the output and adjustable brushes. At least twice I've seen them mixed up by "professional" generator shops, and it cooks the generator when they do this.

With the band off you should be able to trace the output terminal wire back to the output brush.
 
Yippee we have charge - thanks to you good folks. If I ever make it to the US it's beers on me all round. I think it was Robw's advice that finally did the trick - I double-checked the wiring and found that the junction box had been wired mirror-image. I suspect it was wired in Australia by someone who followed the manual that identifies "driver side" and "passenger side" terminals, without taking account of the fact that the car's a right-hooker! The odd thing is that it all worked fine for 16 years, until I did something to upset it. Once I'd swapped everything over, I polarised the genny and bob's your uncle! Thanks again.
 
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