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MG TD TF 1500 - Voltage regulator adjustment

I have a '53 TD with a good generator based on various testing procedures that are on this site and others. I think though, that I have a marginal voltage regulator. When I turn on the headlights the ammeter drops significantly and regardless of engine rpm never shows the needle in the positive position. I checked the voltage across the battery terminals when the lights were on and the engine running it was only at 12.7 volts. Now, whether this is a good test or not, it sure seems to me as if I should have higher voltage being generated. Are there any papers out on how to adjust the regulator? Seems as if there should be some way to perform this function.
Mark Strang

Its in the WSM.
Dave H
Dave Hill

Okay, I take a peek at it. Thanks, Mark
Mark Strang

Mark.
You stated theat the engine was running but was it above 1500/2000 RPM? That's when it should be charging with an output voltage slightly above 13 volts
Sandy
edith sanders

Sandy, I ran the engine at about 1800 rpm and the "output" to the battery was about 12.7 volts. I don't think that is enough to cover the current draw of the headlights.I'm going to check the book to see what I can do. Sounds as if there is a bit of adjustment that can be made to allow the generator to deliver enough current to keep the battery charged. At the moment there appears to be enough voltage/current to keep the battery up to snuff when there are no accessories running. Mark
Mark Strang

Well, I cleaned the contacts again on the regulator and did the testing suggested in the WSM. The regulator is about only about three years old and was supposed to be set at the factory when I bought it. It seems as if the output voltage was set at about 14.0 volts after following the WSM procedures. I made a slight adjustment as suggested and brought the output voltage to the factory spec. It now charges great even with the headlights turned on. It charged the battery to a good level also which it should do. Prior to the adjustment it would only get the battery up to about 12.5 volts. Some combination of the contact cleaning and the adjustment has me the car happy again. Thanks for the input. This problem has been ongoing for a long time. I can now drive with the lights on. Mark
Mark Strang

14V could be OK. I trimmed mine to 13.8 V.
Factory specs for classics is often too high for nowadays batteries.
Old batteries featured higher internal resistors than todays. For this, factory setting was often between 15V and 16 V. Mine was set to 15.4V when I got the car.

With this settings and low internal resistor batteries it often overflows when charging.

And life time is reduced.
I would recommend to keep the voltage between 13.8 and 14V when charging.

Laurent.

LC Laurent31

That is interesting. I've been thinking about this since I adjusted the regulator. Wouldn't it make sense to adjust the output of the regulator to be at zero or a bit more when the car has the max load on it such as headlights? Right now I am always in the 20 range when driving during the day without lights on. I'd like to back the output down a little. It would seem as if I am over charging the battery on a continuous basis. If I backed it off a bit then I would still be in the positive side more than necessary for daytime driving, but not as much. Perhaps I just don't understand what is going on.
Mark
Mark Strang

I might be wrong, but I have found that if the ammeter shows a high charge rate all the time it can be a sign the battery is beginning to fail and a high charging rate is needed to keep it alive. Can anyone confirm this theory?
John Quilter (TD8986) Oregon USA

Correct John,
The charging current is more or less,and neglecting other factors, proportionnal to the voltage between the regulator output and the battery voltage.
If the battery voltage drops down, current increase.
And for Mark, if the regulator output increases,current also increases.

Method of adjusting for 0 Amps when full load is not valid in my opinion. The regulator tends to adjust iteself to 0 Amps when battery is fully charged and whatever the load.

So if you adjust to 0 Amps with full load, you would have to check that the battery is fully charged and in perfect conditions : impossible.

Lead batteries needs to be charged with constant voltage.
This voltage may be chosen between 13 and 15V.
The higher, the larger capcity of the battery but the shorter life time of the battery.
That's why I choosed 13.6 V.


LC Laurent31

This thread was discussed between 15/05/2017 and 18/05/2017

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