Charging light stays on for ages

B

BobTaylor

Member
I have tried searching the forum for the answer, but no luck so far.
I have a 1972 2000SC with an 11AC alternator. When I start the car the charge warning light on the dash stays on until I reach about 30 mph in top, it then goes out and as soon as I start to slow down it comes back on. If I rev it there is the same result.
I know that this car has the remote voltage regulator. I have tried cleaning the terminals on it and the 11AC, no change.
Two questions 1: does anyone have an idea what the problem might be ? and 2: If the 11AC is faulty is it possible and advisable to change it for another type?
I must confess that my understanding of electrics is basic, so please try not to be too technical !!!
Cheers
Bob
 
The warning light is operated by a separate unit, looking a bit like a round flasher unit , this might be at fault and the alternator & regulator are Ok. If you can use a multimeter to check what the battery voltage is when the light goes out , could help to identify the problem
 
roverp480 said:
The warning light is operated by a separate unit, looking a bit like a round flasher unit , this might be at fault and the alternator & regulator are Ok. If you can use a multimeter to check what the battery voltage is when the light goes out , could help to identify the problem
Click to expand...
Thanks, is this flasher type unit the one inside the drivers drop down glove box? If it was faulty would it effect any other warning lights?
Bob
 
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It won't affect any of the other warning lights if it's faulty.

Testing the 11AC system is a lot more involved than with an ACR but the WM gives the procedures for testing the system and each individual part.
ISTR the 4TR control unit is adjustable but I may have dreamt that.
 
harveyp6 said:
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It won't affect any of the other warning lights if it's faulty.

Testing the 11AC system is a lot more involved than with an ACR but the WM gives the procedures for testing the system and each individual part.
ISTR the 4TR control unit is adjustable but I may have dreamt that.
Click to expand...
Thanks, so if my battery is charging I can ignore the light?
 
An 11AC can charge even if the warning light stays on. Check the charge rate to see if that's the case. Ideally get it to work as it should though.
 
Hi Bob, If you need more information give John Bowling senior a ring at Bowling Ryan in Bolton 01204700300. He is an electronics specialist regarding Rolls Royce and he may be able to help you because all the early Shadows had 11AC alternators and used this warning light control. I know this because I was in his company the other evening and he showed us an Indian made copy that has completely different internals. Not adjustable as far as I'm aware Harvey.
Nigel.
 
Thanks Harvey as Bob says something new every day, I have a 1969 Three Thousand Five with 11AC awaiting restoration and notice its not listed nor the Shadow.
Regards, Nigel.
 
Hello one and all, SUCCESS !!!!! I replaced the 3AW unit with an electronic version from Auto Electric Supplies and it has fixed the problem. So it looks like the alternator is ok.
Thanks to all who replied, it is safe to say that I would not have got there with just my Haynes manual.
Now to sort out the starter motor! Thanks ,
Bob
 
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