Classic cars forum & vehicle restoration.

[Rick]

I notice the ammeter on my pickup is registering no charge under revs, nor is a meter that I put across the battery.

First thoughts are:

1. loose fanbelt (unlikely but could be a bit loose)
2. sticking bushes in the dynamo

What else should I be checking? how do I test the control box??

ta
Rick

[Uncle Joe]

Theres an old trick that can help with this one.

Measure your battery voltage, with the engine switched off. Connect the F and D terminals on the regulator together with a bridging wire. Start the engine, and measure battery voltage again, checking if it rises with engine revs. If the voltage rises, the regulator is shot. If it doesn´t rise, check over the dynamo, ie rebuild it.

Dont forget to remove the bridging wire, or you will have a fried battery!

[Guest]

The Ford is a 6v positive earth, does that make any difference to the test?

also, do leads on F and D terminals need disconnection from the regulator before the bridging test, or leave them connected?

ta
Rick

[Uncle Joe]

I have tried this method on both positive and negative earthed dynamo systems, but never on 6v systems. Even so, it shouldn´t make any difference whatsoever. A Regulator, or Control Box is nothing more than an automatic switch, and all you are doing is bypassing it and connecting the dynamo directly to the battery. You should leave all of the wires connected when you do this test, but also remove the bridge immediately after wards, as the battery will discharge through the dynamo.

There is another way to test. Remove the regulator cover, start the engine and run it at a fast tickover. Close the cut out points by pressing the top "flap" down. The cut out "flap" is the one that CLOSES a pair of points. If the ammeter shows a charge, the regulator is faulty.

Can you tell I´ve been around cars for a long time?

[Guest]

Hi Joe

Got it sorted in the end, swapped the regulator for another spare but no improvement. Had a read of the workshop manual (always a last resort!!) and like you say, did the voltage reading across the leads running from the dynamo - nothing. Pulled the dynamo off and cleaned it out inside - lots of claggy stuff, a mix I think of bush dust and oilyness. Freed up the bushes which were sticking in their guides, and cleaned up the commutator a bit. Bolted it all back together and - nothing, at least until I re-fitted the original regulator, then it showed a healthy charged - phew!!!

The engine is still running like a bear with a sore head mind - but then again it always has!!

cheers,
Rick

[Uncle Joe]

I´ll bet that you didn´t practice the black art of undercutting when the dynamo was stripped though, did you?

[admin]

Hi

I had a look at the commutator while it was apart and it looked ok to me!

Rick.

[Uncle Joe]

Its good that the commutator looked good. I think that you may be aware of what I am about to put, but here goes anyway!

What some people may not realise, undercutting does not refer to the copper segments, but the gaps in between them, and this is a common problem area.

[Rick]

Hi UJ

Yup I knew what you meant, but good idea to clarify nonetheless!! the gaps looked good and clear (if thats the word?!)

So at least thats sorted, all I need to do is make the thing run properly again (suspect points have closed up)

cheers
Rick