GM alternator swap

I recently got my new (old) Jag running, and shortly after it was running for a bit I noticed the battery light came on and the voltage was dipping. Checked everything with a meter and it deffinetly was. The car has a lot of miles on it so I don’t doubt that it needs a new Alternator. I am looking at replacements, and notice that the original doesn’t look much different than a GM alt. Google searching of came across vague info on the swap, but nothing exact.

Has anyone completed this swap? My main idea is that I can get the GM alt from any parts store no matter where I am at. I hope I am not upsetting purists, but I want to drive this car and not have to worry about being stranded because of parts.

Have you taken the alternator out and had it tested?

No I haven’t, I plan to pull it out today. I am just preparing for the worst. If I have to replace it then I would rather go with a GM.

If you can find a drop in equivalent then go with that, but if you end up fabricating brackets and such then it becomes a bother.

The alternators on these cars are pretty reliable. If it were me, I’d be more apt to take it to an alternator shop and have it rebuilt rather than taking the time and energy to install a GM one. Having worked an auto parts store for several years when I was younger, I’d be more wary of having a GM alternator, even if it happens to be a more common part number.

After tearing into it and seeing where it is, trying to fit something different there would be a nightmare I think. I can buy a replacement from rock auto for pretty reasonable. I do find it odd you have to adjust the tension on a ribbed belt. That also looks like it’s a pain to do.

Depending on the year of your car, Jag did upgrade the output on the later cars by about 20-30%
Not sure if that helps at all.

My 1992 xj40 was a big upgrade over the 1988 to 1991, trim , wiring and better reliability.
I always go GM on the OLD STUFF but in all honesty stick with the original rebuild or even new.
The brackets and harness are pretty unique to THAT jag.
Plus there are many feeds to other components it the system.
The1988 to 1994 had the LONGEST amount of wires in Jaguar history at the time which the xj300
did away with to a 1 wire harness system.
Stick with a Jag alt and CLEAN ALL YOUR TERMINALS.

I’m sure the stock alternator will be sufficient for my needs. I am going to install a 5 channel amp in the car, that will be the only extra load. The amp is not crazy so I am sure the stock alternator will do fine. I am going to remove it tomorrow, from what I have read that looks like a chore. I may tear into it myself to see if I can find a problem before I buy a new one.

I am new to Jags, but what extra would the VP have?

It has been several years since I replaced mine, but I don’t recall it being a big deal. I mean If I can do it, anyone with a modicum of mechanical aptitude should be fine. :blush:

VDP had extra power switches on the back of the front seats so if you were being driven you can push the seats forward without getting in the front.
Also many VDP had heated rear seats a new option back in the day.
Corner coach map lights and a LARGE cigar style lighter in the back as well.
All pulling more amps, by todays standards its nothing.
Mike is right by todays standards swapping out the alt is easy.
Good luck and please use the stock alt in this case.

Its not that difficult of a job, but I would recommend doing it from the bottom. Much of it will depend on the condition of your tension adjuster. If the nut doesn’t turn easily, it can be time consuming.