TR6 TR6 alternator output

[AltaKnight]

The Lucas alternator on my 73 TR6 was on it's last legs, not charging and howling bearings.
I looked at replacing it with a more modern one but didn't like the idea of being not original (not to mention screwing around with the wiring changes and brackets) so I got it rebuilt.
It looks wonderful, just like new and charges great but I'm wondering about the output voltage.
I've checked it with the multimeter and it's reading 14volts with engine off, 17.5volts at idle and 19volts at speed./ubbthreads/images/graemlins/shocked.gif
Everything has been working fine including the radio and it doesn't seem to be blowing anything out, is this voltage about right or do I have a bad voltage regulator.
I have a new battery and the voltage reads steady, not swinging. Since the dashboard guage only goes to about 16V it's right over and has me worried. /ubbthreads/images/graemlins/frown.gif

 

[piman]

Hello Graham,
that voltage is too high, it should be regulated to 14.7volts.
The alternator has a built in regulator so it sounds as though this is not functioning, so I suggest you return it to the re-builders. That sort of voltage will damage the battery through overcharging.

Alec

 

[Paul Johnson]

Are you sure the meter is calibrated? Sounds suspicious that the alternator is putting out 2v with the engine off.
Might try another meter, or that meter on another car before ripping the alternator apart.

 

[dklawson]

I agree with both comments. An at-rest battery should measure between 12-13 volts. The alternator should operate at a regulated level of about 14.5-14.7 volts. You'll boil that battery dry quickly with the alternator supplying 19 volts. Make sure your measurements are taken with a multi-meter and not the dash gauge as it may be well out of calibration.

BTW, it's my understanding that due to a parts shortage (as the result of a British factory strike of the period) SOME early 1970s TR6s can be found with Delco alternators (from the factory) instead of Lucas. It's also my understanding that the shortage was not long and the substitution only lasted a couple of weeks during production. Is this urban legend or has anyone else heard this before?

 

[martx-5]

The alternator is overcharging. The at rest 14V shows that the battery is overcharged. If you continue to run it this way, the battery will be history real soon. As suggested above, bring the unit back to the rebuilder.

 

[AltaKnight]

Thanks to you all.....
That's a good idea to test a different car and compare.
I'll try that tonight.

 

[Geo Hahn]

Also -- you may find that the 14V you are reading at the battery drops to something like 12.7 after the battery has sat overnight. Overcharging will cause a battery to read higher for a bit right after it is removed.

 

[Mark_Gibson]

Doug,

My 70 TR-6 has a Lucas alternator, built in Feb 1970, CC52403L U, so not sure, maybe earlier build that year?

Mark

 

[dklawson]

My info on the Delcos in TR6s is purely hearsay. If anyone has heard of it before please let me know if it's true or not... just for curiosity.