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TR2/3/3A I just installed a rebuilt C39 Generator on my TR3

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Frank_D

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I need a little advice. I have just installed a rebuilt C39 generator on my 59 TR3A. I am sure that the C39 is the correct model and it comes from a reputable shop. It is replacing an after market C40 unit that had a bad field coil. I had to replace the Lucar connectors on the harness with closed eyelets to work with the threaded posts and nuts on the new unit. The installation was pretty straightforward.

On start up, the ignition light was brightly flashing and both ammeter and volt meter were fluctuating rapidly. Immediate shut down! Do I need to polarize this new generator or is there a more serious issue? My car is negative ground.

Thanks guys......... FD
 
Since you apparently do not know what polarization it has you should polarize it for negative ground. If it was already that way, then it won't hurt anything to have done it again.

A generator may get polarized on start up if it is incorrect polarity but, of course, such a brute force method is not recommended.

I do not know what the flashing light might mean but if in doubt that all is well you can disconnect the generator and run the usual tests shown in the manual to see if the numbers are per spec.
 
Yup, sounds like polarization to me. It is polarized to positive ground, so when you first start the engine, it starts generating negative voltage. When it gets to -12v or so, the cutout tries to close (the relay doesn't know anything about polarity), but there is +12v on the other contact. The dash light effectively displays the voltage across the contacts, so it is seeing 24v, hence the bright light.

Evidently, when the contacts close, the resulting current is causing the cutout to open again (it also has a current winding) without having polarized the generator. So it still builds to -12v and the cycle repeats. Kind of interesting, I've not seen one do that, but the theory fits the facts.

Oh yeah, you might want to inspect those cutout contacts, and clean them if they are burnt. Also wouldn't hurt to make sure the control box is for a C39 instead of C40. They aren't quite the same, and Lucas warned against trying to mix them. Look for the Lucas part number on the side of the base. I believe it should be 37182x (where x is a letter indicating the revision level).
 
Thanks to both of you regulars on the forum. I was hoping I would hear from you and there you are. I just did the polarization followed by a start up. All appears to be good on a short test drive. I will check the VR numbers to be sure, Randall. I have a spare and will check it in case. Thanks for the lessons and advice.

Frank D....... Canada
 
Just checked my spare VR and it is a 37182M. The one I am running in the car is a Moss unit with screw terminals. I will inspect it tomorrow but I have also asked Moss for an opinion on their part application versus the Lucas 37182 Model. Randall, your knowledge is humbling but so much appreciated.
 
If someone should get a bad field coil reading most of the time it will prove to be a short to the yoke, where the cotton wrapping has deteriorated. Take out the coils and if they haven't arc welded themselves together at some point and test them. If good just repaint the exposed area with some high temp varnish (art brush) and rewrap the local area. If all of the wrapping is shot, 3M makes an excellent 1/2" fiberglass tape which just does pass thru the hole when you start. Only remove the old wrapping a couple inches at a time in advance of your new taping job.
 
So after a couple of days I went for a two hour drive on Tuesday and the TR3 ran like a clock. It was a great day and I was a happy dude. On Thursday morning we had loaded up the TR ready for a trip to upper New York State. Rolled out of the garage with top up (rain nearby) and were on our way. Only 1/4 mile from the house cough and sputter and then she died. Seemed like fuel which was easy to refute. I think it is the coil as it was hot to the touch after only 5 minutes of running. I think my earlier startup with a positive ground generator may have fried it. Comments on that theory? Friends push home and into the barn.

No time to swap the coil with my spare so we loaded the SUV and headed out with 30 other Triumphs.
 
Frank_D said:
...I think it is the coil as it was hot to the touch after only 5 minutes of running. I think my earlier startup with a positive ground generator may have fried it. Comments on that theory?.
Click to expand...

I believe it could be a failed coil but I doubt your experiment with reversed polarity did it. The coil doesn't much mind being connected backwards -- though the resulting spark will be tough on the points the car will run okay with that set-up.

Frank_D said:
...No time to swap the coil with my spare so we loaded the SUV and headed out with 30 other Triumphs...
Click to expand...

For a quick swap you do not have to have the coil mounted in the bracket -- I carry a couple of small bungees with my spare coil so I can just strap it onto the mounted coil and move the wires over. Have used duct tape for this (messy) or you can even just lay the coil nearby (seems like once I was able to cradle it among some stuff).
 
What he said.
 
Thanks to both of you gentlemen. As it turns out, Randall, I am running a Lucas Sports Coil and based on your comments on another thread, they are not that great. My spare is not. I will report results on Monday afternoon. With files and 30 TRs in Ellicotville, NY. No TR3's though!
 
Thank you gentlemen for your sage advice. Comforting to have this kind of advice. Home now from the weekend with 30 other TRs and back under the hood. I thought I would do the simple thing first and re-installed my mechanical points to have a go at that. Well it was the Pertronix points that had failed as they are known to do. I had not played with mechanical points for the 13 years these Petronix have been in place. The old ones went it easy and she fired up right away. End of another story. Thanks for the advice.

Frank D........
 
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