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MG TD TF 1500 - TD Voltage Regulator

When I turn the headlights on, my ammeter shows a strong discharge. I've checked the generator output, and it's fine. So I conclude the voltage regulator needs adjusting. There are two adjusting screws, one for cut-in and one for cut-out.

Am I right in concluding that the cut-in needs to be adjusted and which way, increase or decrease the cut-in voltage?
Thanks
gary dewitt

Gary - Are you having a problem with your battery discharging? If not, I would investigate the "strong discharge" shown on your ammeter before messing with the regulator. The ammeter will register any large current draw and the one in your T car is almost 50 years old (if not more) and may not be the most accurate instrument in the world. If you are going to try adjusting the regulator, read the shop manual section on doing the adjustments and understand the procedure before proceeding. I have owned a number of TDs over the past 40 years and have never found it necessary to adjust a regulator (that is not to say that it is never necessary), they seem to be like the energizer bunny - they just keep going and...
Good luck, Dave
David DuBois

Gary, at what RPM does it happen? It is normal at idle to discharge a lot with lights on. Above 1500-2000 it should be zero to charge. These ammeters are flaky and can't be totally trusted. DAvid asked the key question- does the battery run down? Of course if you flip on the lights and it pegs to negative, there may be a short.
George Butz

This is somewhat off on a tangent. Has anyone designed or have plans to replace the internals of the voltage regulator with modern electronics?

I was wondering if you could take an old regulator body and add the appropiate diodes, etc to the internals leaving the external stuff alone.

Bill
Bill Loubiere

Thanks for the feedback.
Here's some more information. When I start
the car, the ammeter reads a good charge.
After the car warms up and I'm on the road
a while, it is at zero, and often below.
The battery does run down. I've also checked
the fan belt. I'd like to provide more info
but we still have feet of snow here and I'm
recollecting from last summer.
Gary
gary dewitt

Maybe off tangent too but.. I have a 53 TD and was experiencing discharge problems. I adjusted the regulator as per the shop manual. I used a voltmeter and adjusted the adjusting screw until the voltmeter flicked and stabilized between 15.8-16.4V (at 20 degrees C). After a while I noticed the battery was bubbling over. I took the manual to an electrical engineer friend for review and he said that the setting seemed to high and that I would boil the battery. So is the shop manual wrong or have I done something wrong? Do modern batteries have slightly different voltages Then those used in the fifties? Thanks
Tim Mayor

Gary - It sounds like your generator is dying after it warms up. To check this take the car out and run it (after all that nasty white stuff goes away of course) until the charge on the ammeter drops off, then take it home and run the following check. Disconnect both wires from the generator, then jumper the two generator terminals together. Attach a volt multimeter (set to the 50 volt scale) between the jumpered terminals Negative lead to the generator terminals, positive lead to ground (this assumes that your car is still positive ground - reverse the meter leads if your car is negative ground). Now start the engine and watch the meter while bringing the engine revs up slowly. If the generator is working properly, the voltage should continue to climb as the reves go up. Take care that you don't let the voltage climb beyond 20 volts. If the voltage never gets above 12 volts (often times much less) regardless of the engine RPM, then you have a bad generator. If the voltage goes up as the RPM increases, then the regulator is your problem. In either cases, I would recommend that you take the offending item to a local Lucas approved electrical repair shop for repair or adjustment. Look in your local yellow pages for such a repair shop. The adjustment of the regulator is somewhat tricky, as Tim found out and if not set correctly can lead to battery damage.

Tim - Speaking of your experience, did you recheck the output voltage after you had tightened everything down in the regulator after having adjusted it? It is quite possible that the adjustment slipped when you tightened the lock nut down.

Good luck - Dave
David DuBois

Gary - One further item. You mentioned that you checked the fan belt. It has been my experience, that when people say that it can be transelated to, "tightened the fan belt". If this is the correct transelation for your statement, you will need to loosten the fan belt. It should be loose enough that the fan/water pump pully can be slipped by hand when pulling on a fan blade. Any tighter than this and the tension on the generator pully will cause premature wear on the front bearing and greatly accelerated on the rear bushing. In fact this rear bushing wear could be the cause of your present problem. Good luck - Dave
David DuBois

Re; don't let the voltage climb above 20 volts. This happens very rapidly, at low revs, 1,000-1200.Check with Abingdon Classic's/U.S.A. W. Redding, C.t. [203] 438-6865. Dave is very helpful, & has more experience on T types than you will ever need! Safety Fast! Len
Len Fanelli

This thread was discussed between 17/03/2001 and 18/03/2001

MG TD TF 1500 index

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