Up until recently, all has been working great on my '53 XK120 DHC. Last week, the IGN light came on while I was driving her… and the AMP Meter dropped very slightly below “0”. Note, battery new, fully charged, and approx. 2 years old. Also, all gauges redone by Nissonger.
Since then, I replaced the generator bushes (Moss Motors pn#872-470), the belt (Gates B36), and a new Regulator from SNG.
Today, after completing the install of all of the above new parts, I started the engine. Here are the facts after starting the engine:
Temp outside is 55 degrees
Start idle was 1,200 rpms cold (IGN Light on and AMP Meter was very slightly below “0”)
Once warm, and cold start shut off, idle was 700 rpms (No change in AMP Meter reading)
Pushed gas pedal until RPMs reached 2,000 and IGN Light still on, absolutely no change/movement in AMP Meter)
Turn on headlights and AMP Meter drops to ~ -13. Step on gas pedal and absolutely no change in AMP Meter.
Based on the above… what do you all think could be the issue? Open to any suggestions.
If you hadn’t said “new regulator from SNG”, I would have said the cutout on the regulator was stuck on.
Better review your regulator wiring, maybe you got something on the wrong terminal.
Disconnect both wires on the back of the generator and measure from each
terminal to ground. You should get around 6 ohms on the “F” terminal and
close to 0 ohms at the “D” terminal. If that’s good then it wouldn’t hurt
to polarize the generator by connecting a wire from the ungrounded side of
the battery to the “F” terminal for about a second. Connect the generator
back up, making sure the F terminal wire goes to the F terminal on the
regulator and try it again.
Mike Eck
New Jersey, USA www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2
Once I disconnect the wires from the back of the generator, do I simply check the ohms with the key off? Do I reconnect the battery positive cable to do your test??
Bob, your regulator wiring looks to be correct according to the wiring diagram W94602.
You can leave the battery connected and key off but don’t touch those two loose generator wires to anything while you check the Ohm resistance to ground of each of the two generator connection posts. If you are nervous about this step you can disconnect the battery.
You need the battery connected to do the polarization, and leave the key off.
I have polarized a generator by touching a jumper wire across terminals A and F on the regulator.
But I got to wondering, does the regulator naturally do this the first time the contacts close?
Did all the suggestions and alt light still on and amp meter slightly below 0.
Removed generator again and took it to an old shop in Memphis that specializes in generator, starters, etc…
They bench tested, again zero output!
So no shipping it to Star Auto Electric in CA. They will restore with all new components. I dont think these are sold any longer. Most seem to be sold as “look alikes” with an alternator inside. I want to keep mine as a generator along with my original brass tag with all markings…
Let me know if you have any questions.
Will keep you all posted when I get the restored gen back…
Thinking about it some more, I recall you replaced the brushes. Is there any chance there is some wire connector end touching ground in the end cover that shouldn’t be?
Just to continue this thread… I did all of the tests, no luck.
Removed Generator and took to a local Memphis shop that specializes in testing and repairing old Generators, Alternators, Starters… Unfortunately it tested bad… So, I sent it off to a family owned/run place in CA for restoration. If anyone is interested in vendor name, pls pm me off-line.
So now awaiting my restored generator so that I can reinstall.
Good luck with the generator rebuild. I have used a multiple generation family-owned/run shop in Van Nuys, California a few times with complete satisfaction on generator rebuilds for late 1940s, early 1950s Jags.
