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Triumph TR6 - troubleshooting alternators

RECENTLY PURCHASED A 73 TR6. I NOTICED THAT THE voltmeter DOESN'T MOVE TOWARD CHARGE AT ANY TIME AND BATTERY EVENTUALLY RUNS DOWN. I'M A LITTLE RUSTY ON TROUBLESHOOTING ALTERNATORS BUT DID DETERMINE THAT THIS IS A THREE WIRE LUCAS. THE TWO LARGER BROWN WIRES ARE ALWAYS 12 VOLTS POSITIVE. THE SMALLER BR/GR WIRE DOES RUN TO THE IGN. LAMP WHICH NEVER LIGHTS UNLESS I UNPLUG THE BR/GR WIRE FROM THE ALTERNATOR AND GROUND THAT WIRE. I THINK THE ALTERNATOR IS BAD BUT DON'T WANT TO BUY A NEW ON UNLESS I HAVE TO. I HAD THE BATTERY TESTED, ITS GOOD. CAN ANYONE ADVISE ME AS TO THE ABOVE? THANKS MIKE
mike byce

Maybe the simplest way is to take it to the auto parts place or auto electric shop. Most do tests free.
Tom

While your at it check out having it rebuilt....I had my starter rebuilt 2 years ago for less than a hundred.

Charlie
Charlie B.

Mike,
Hook up the volt meter to the battery. It should read around 12.5 to 13 volts. Crank the engine. During start the voltage should not drop below 9 volts. When the engine starts the voltage should rise to 13.5 to 14. This is the alternator recharging the battery after start. There are other checks but this is the simplest.
Joe
Joe

Disconnect the battery while the car is running. If the car still runs, the alternator is good and the battery is bad. If the car dies, you've got a bad alternator and possibly a good battery.
benji

Benji,

That was a common test to check alternators on older American cars. Lucas alternators are not known for being as robust. That proceedure will easily cause damage to the Lucas. In my experience a weak battery can kill off a Lucas pretty quickly.

It's best to do as others suggest and take the alternator in to a REPUTABLE auto electric shop/rebuilder. Many of the chain stores (Autozone, O'Reilly, Advance, etc.) don't have all of the adapters to connect up the Lucas. Although some of the chains offer lifetime warranty on a rebuilt unit. Don't know if that will apply here or not.

BTW - whenever a Lucas dies on me now, it gets replaced with one from a Saturn. I have one on my daily driver (MGB). It's gone a year and a half without a hiccup, plus it's keeping a 10 year old battery working as inteded.

Tom
Tom Sotomayor

"That was a common test to check alternators on older American cars. Lucas alternators are not known for being as robust. That proceedure will easily cause damage to the Lucas."
Good point Tom. I forgot how pathetic the original Lucas p.o.s. alternator was and how many heartaches it gave me. Since replacing mine with a 65 amp GM alternator, I have not had no problems. (Sorry you original guys).
If it means anything to you Mike, if you can't do a simple test of the alternator running your electricals because it may put to much sTrEsS on it, replace it with a more reliable alternator that won't give you the heartaches I had.
benji

I SENT THE ORIGINAL QUESTION. I APPRECIATE ALL THE INPUT. I WANTED TO TEST ALTERNATOR IN A MORE DECISIVE MANNER BECAUSE I'M KIND OF A DETAIL PERSON. ANYWAY PROBLEM IS SOLVED. I PICKED UP A REPLACEMENT ALTERNATOR AT A LOCAL TRIUMPH SHOP(THEY'RE STILL AROUND). IT CAME COMPLETE WITH THE FAN AND SHEAVE FOR 100.00. I INSTALLED IT AND IT WORKS. THANKS AGAIN.
mike

Mike, I am weighing in kind of late on this one, but I did what you did. I got an alternator on sale from TRF for less than $100 and it fixed the problem. I don't think it is worth going to too much trouble repairing a 30+ year old thing when you can get a newly rebuilt one for that kind of money.

John
JL Bryan

This thread was discussed between 31/08/2006 and 06/09/2006

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