Question regarding alternator capacitor

[Donald H.]

I am rebuilding a Delco Remy alternator for my 66. I purchased a rebuild kit which came with a capacitor. The capacitor has a plain end. The end of the original capacitor is stamped 1959455 and 5MF. I assume the first is a part number and the 5MF is the capacitance in microfarads.

Long Island sells a reproduction capacitor with the correct stampings on the end, so I purchased one.

When I tested the original I get .5 microfarads, I also get .5 microfarads when I test the one with the plain end. When I test the LIC reproduction with stamped end, I get .18 microfarads.

I don't know enough about electronics to even be dangerous, so my question is, is it OK to use the LIC one in the rebuild?

Thanks,

Don

[Joe L.]

Re: Question regarding alternator capacitor

I am rebuilding a Delco Remy alternator for my 66. I purchased a rebuild kit which came with a capacitor. The capacitor has a plain end. The end of the original capacitor is stamped 1959455 and 5MF. I assume the first is a part number and the 5MF is the capacitance in microfarads.

Long Island sells a reproduction capacitor with the correct stampings on the end, so I purchased one.

When I tested the original I get .5 microfarads, I also get .5 microfarads when I test the one with the plain end. When I test the LIC reproduction with stamped end, I get .18 microfarads.

I don't know enough about electronics to even be dangerous, so my question is, is it OK to use the LIC one in the rebuild?

Thanks,

Don

Don------


The purpose of the capacitor is radio interference suppression. It has no other function. I would expect the 0.18 MF capacitor to be less effective in RF suppression than the original.

[Donald H.]

Re: Question regarding alternator capacitor

Thanks for the response.

[Richard M.]

Re: Question regarding alternator capacitor

Don, If I bought a $20 RF capacitor from my vendor that was spec'd to be .5MF and it read .18MF, I'd return the part and get either a full credit or a correct part replacement. The lower value will probably be unnoticeable in function, but in principle it's wrong IMO.

The problem you're going to have is convincing the vendor that the part is defective, and in particular.... that vendor. You'll probably need to have your capacitance meter calibration checked by the Bureau of Standards Laboratory, with documented and notarized signatures and full seventeen page data report.

Most folks that sell original or reproduction capacitors are more concerned with originality, correct markings and condition versus function.

Also, the repro is actually marked wrong. The "." in the ".5MF" on the original devices is very hard to read, and the manufacturers that repro'd the part didn't notice it and left the "." off in error. I see it on most repros. For any other repros that you get that are mounted in view of the judges, you can make your own "." to avoid getting a "DOT" on your scoresheet in judging.

Rich

[Joe R.]

Re: Question regarding alternator capacitor

Hi Don,

I do know a little about electronics, but nothing about the capacitor you're interested in. I would say use the same value (0.5 microFarads) capacitor to ensure the the circuit will continue to operate as designed.

Joe

[Donald H.]

Re: Question regarding alternator capacitor

Don, If I bought a $20 RF capacitor from my vendor that was spec'd to be .5MF and it read .18MF, I'd return the part and get either a full credit or a correct part replacement. The lower value will probably be unnoticeable in function, but in principle it's wrong IMO.

The problem you're going to have is convincing the vendor that the part is defective, and in particular.... that vendor. You'll probably need to have your capacitance meter calibration checked by the Bureau of Standards Laboratory, with documented and notarized signatures and full seventeen page data report.

Most folks that sell original or reproduction capacitors are more concerned with originality, correct markings and condition versus function.

Also, the repro is actually marked wrong. The "." in the ".5MF" on the original devices is very hard to read, and the manufacturers that repro'd the part didn't notice it and left the "." off in error. I see it on most repros. For any other repros that you get that are mounted in view of the judges, you can make your own "." to avoid getting a "DOT" on your scoresheet in judging.

Rich

Rich,

Good advice, but I'll probably just eat the cost. By the time I pay postage to send it back, it's hardly worth the effort.

Since the original still tests good, I've cleaned it up, buffed the rust off the bottom and lower half, and just put it through my copy cad plating. If it looks OK, I'll just re-use it.

Don