Hi - I am trying to troubleshoot a strange situation. My car will start in an instant and the voltage gauge with slowly climb to 13v indicated. It will remain at this point until I put it into gear and commence driving - then it will start to drop off - especially when the lights are on, etc. At NO time does the battery/alternator light come on in the dash once running. It WILL eventually die due to being on battery only (2+ hrs driving). It tends to hover around 10v or a tad less. A few weeks back, it would occasionally climb back to 13v but that is no longer the case. I have begun going through and cleaning various ground points. It certainly helped to brighten my low beams, but that's about it so far. Any thoughts out there on a root cause? I am not convinced of a "bad" alternator or regulator due to it routinely going to 13v upon cold start every time... This car has sat for at least several years - I have resolved a number of other gremlins traceable to sitting too long thus far and am unwilling to just throw parts at it (alternator, etc) without thorough investigation..
Thank you

Scott

 

The gounds, and also the supply connections should be #1 on any list.

Then get hold of a DCM (Digital Volt Meter) and connect it to the battery. This will give a very accurate reading of what the system is actually doing. The dash gauge is a good guide, but more accurate readings make it easier.

The brush pack/voltage regulator inside the alternator may be a prime culprit.

A slack/slipping alternator belt will also give the results you describe.

Th engine earth strap should be checked for 100% integrity.

The +ve cables on the back of the alternator may have a crazy high resistance in them, and that will also give the same results.

Unplug the small wire, switch ON the ignition, read the volts in that wire. It should be battery voltage, or very close.

After that the actual "excitor" diodes inside the alternator may have issues, and that will cause the alternator to be unstable in its charging ability.

 

I would add to Grant's precise comments. I made a patch cord to connect my VOM through the cigar lighter outlet. Thusly, I was able to read vehicle voltage under various loads and RPM's in real time. My alternator was exonerated and the battery convicted. a new one fixed all manner of weird things.


But, caveat, Jaguar electric mantra Clean, tighten and lube the electrical connectors and grounds.


I like petroleum jelly for this task. Dates way back with me for lube on point and condenser distributor rubbing blocks and battery posts.


Carl

 

If you are getting no ignition light when the ignition is on but engine not started then check the warning light bulb and wiring to it.

 

sounds like a GM alternator! ask me how I know...

I agree with Francis, but the only way to really find out if it is the alternator, is to replace it. HINT: don't install another GM alternator. They suck.

 

Jose:


Millions of Delco alternators suck???


But, if that is your opinion, so be it.


I ain't gonna change out the big delco on my LT1 for a Lucas unit. Or whatever the heck brand is in my mani miled Jeep. As the starter is Mitsubishi, a guess would be the alternator is as well. Mitsubishi and Chrysler had a working relation at one time...
Mebbe still do.


Naah, verify before slapping parts on.


Carl

 

Carl,
I understand you love GM alternators but my XJ-6 doesn't.

 

Love, well, not really.


Alternators that work are all I ask, genus, whatever. Well, except for the availability and price issue.


I still have a jar full of Delco rebuild stuff.


Carl

 

Carl,

I just came back from Pull-a-Part and got what they call a 3G alternator for my Ford Aerostar minivan which came with a 2G alternator and was starting to show its age.
$31.00 al included. (yes I pulled it myself from a Ford Expedition).

goodness sake, what a difference. No voltage drop when everything is ON, (a/c, headlights, stereo, front and rear blowers).

the 3G is a larger case puts out (supposedly) 130 amps as opposed to the 90 of the 2G.
it mounts in the same place and the same way as the 2G.

unfortunately no XJ-6 there.

but don't think I love Fords, they are the biggest garbage on the road today, just that I need a rear wheel drive minivan to haul my music equipment to weddings / parties, etc.

I don't want anything front wheel drive.

 

AAAH, I cut my teeth on a pre blue oval car. 1923 FORD T Roadster pickup. A non running derelict that my parents allowed as probably safe for a 15 year old. Much to their chagrin/pride I got it running. circa 1946. I sold it circa 1948 as a quite hot 27 fenderless Roadster. A HOT ROD!!!


Alas, the last Fords here were a 85 Ford F150 4x4 and an 88 Tbird. Both immensely competent.


Not to mention the "Hot Rod of the Forties" project before the Jaguar.


Of all the cars I've had, either owned or furnished free, only one was a FWD. 94 Olds Achieva. Not bad, it's OHC quad Four was close in resemblance to a four banger OFFY.


No need here to haul musical equipment. I am not only hearing challenged, but tone deaf. But, I do enjoy good music. Not the mere noise that seems popular nowadays.


Does your Jaguar really care how the volts are produced?


Good luck with the big amps for the minivan. But junk yard electrics may be no better than the ones you replace????


Of course, nowadays, a rebuild is ??? as well. and a lot of Asian electrics are just as bad or worse. Sure hope my Malysia built new starter turns out OK!!


Carl

 

yes Carl, I agree about junkyard replacements of alternators, but I have 30 days to exchange it, and I think I got lucky, sometimes I do. I've been testing it at night with both blowers On, radio ON, headlights ON, auxiliary lights ON, and it has remained steady at 13 volts, so far so good. If on day 29 it starts to fail on me, back to the junkyard I go. For $31. bucks it's a steal.

my favorite Ford is the 1933 Sedan, (Bonnie and Clyde's??) but I was referring to modern front-wheel-drive Fords, not the rear-wheel-drive antiques of the 1930's. Actually the 1930's is my favorite period for any car.

here's my 1997 Aerostar 4 liter V6, (last year they made them), sorry don't mean to hijack this thread.

 

To further the hijack. I've owned 30's era cars as well. 30 Ford A converted from coupe to topless roadster, 31 Studebaker Commander four door, 31 Studebaker Dictator coupe, 34 Chevrolet tudor standard, 37 Ford Fordor, 34 Ford 5 window coupe, 34 Ford four door....,


Each unique in it' own way, but with one common feature, lousy brakes. well, the Model A's were not that bad.


Your van doesn't look all that mini!!!


Carl