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Constant Failure of Voltage Regulator. 1951 Cub

A

Al Sutherland

New User
I have replaced the 6V voltage regulator on my 1951 Farmall cub three times this year. Nothing is new on the tractor (i.e. same wiring, electrical system & parts that have been on the tractor for years). Symptoms are that the regulator works fine for a month or so, then it stops charging. I tap the regulator and it works for something like 15 minutes and then stops charging. I also re-polarize the regulator which, again, gets it working for a short while. Finally it quits completely and I can do nothing to get the regulator to work. There is never any evidence of what has failed - no burn smell, everything clean and new looking, contact points look clean and are easy to work with my fingers.

What might be causing this failure and is there a way to detect what is happening (e.g. measure voltage at some point)?
 
I would suspect a bad ground or loose connection somewhere in the charging loop that manifests itself as a no charge condition. You mess around with the regulator and re-make the bad connection that goes a while then gets crossed up. The poor connection may eventually take out the regulator because it's grounding or charging through something it isn't supposed to. Example I burnt the speedometer cable off of an EZ-Go golf truckster, the problem was a bad chassis/engine ground cable so it was trying to ground through the speedometer cable, speedo cables don't carry that much juice, much more than 5 amps they get hot and smell bad.
 
First you never polarize a regulator. What is the Delco Remy # on your generator as you need the regulator thats made for that generator. You should read battery voltage on the batt post with engine off and when its runnng it should read 7.2 or so make sure your regulator is grounded to the gen and the gen to ground also. Where are you getting the regs. Go to Car Quest as they are made in the USA.
 
Next time it quits, don't touch anything. Get a good little wire with a clamp on both ends and ground the field terminal of the generator to a good ground. If it starts to charge immediately, your problem is indeed in the regulating circuit be it poor ground on reglator or bad wires or even poor ground of generator. But, if it does not charge immediately, polarize generator and if it charges then, with field still grounded, your problem is in the generator or wires to generator. The polarizing sends a current through and poor connections will wake up. One very common problem, especially with rebuilt generators is high mica on the commutator or excessively hard brush's. You want a nice soft 3rd brush so it makes easy contact.
 
Several decades ago, my 57 Olds burnt up the wiring harness and generator after being parked for a half hour. Late in the days of generator production, some manufactures began running a small ground wire between the gen and regulator. I think that my Olds problem happened because of poor grounding between these. If I had your problem I would put in a #14 or so wire, here; It does not even need to be insulated, this is a simple fix.
 
That is just about the normal life span of a lot of replacement regulators today. I usually fine poor connections inside the regulator, usually at the contacts. After three replacement ones on my Super C, I cleaned and adjusted the original Delco Remy unit. It has been working again now for a couple years.
 
Thanks for the advice. Been getting regulators from a local IH dealer. The regs are the same that I've had for years. I do agree that I must have some sort of ground fault. Thanks for your specifics on where to look for the fault (Reg to gen and gen to ground). I'll check that out.
 
Thanks for all the good advice. I'll be following your directions very soon. Seems like a ground fault is the thing everyone points to.
 
You don't have to thank everyone individually. The forum software removes all the quoted information so we have no idea who you're talking to.
 
Use your volt meter to look for poor connections with the engine running.A poor battery cable connection can let the voltage run high and burn resistors in the regulator plus open up the shunt coil on the cutout section.Check the battery with a hydometer.
 
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