Hello.
My '87 sat out all winter. Just charged the battery. I reads 12.8V. With the engine idling at about 1000 rpms, the voltage across the battery reads 14 to 14.2v (all accy's off). With all accy's on, the voltage reads about 13.05V.

Is this good enough?

Thanx for listening,

George

 

George,

You appear NEW, so welcome aboard.

The dash gauge is really only a "guide", and many factors affect their accuracy, or lack of.

The battery reading is fine at idle, maybe a tad high, it means the alternator is "excited" and doing what it should.

Most alternmator test readings are done at 1500rpm, and always across the battery, as you have done.

With all the odds and ends on at 1500rpm +/- a bit, I am usually happy with 13.5v or better. Too high is going top boil the battery and destroy it.

Most, in my time do read that 14.2 soon after initial start up, and settle within about 10 minutes to about 13.8 unloaded.

Low volts at idle with anything switched is considered "normal" on these older style alternators.

The 115amp Bosch on my V12 sits at 13.6 no matter what revs, or what is on.

 

Heh heh. Good enough, but barely.

Jaguar really should've specified/used a higher output alternator for these cars as the 65amp unit used is marginal when you have lights, blower, rear defogger, etc in operation simultaneously.

I drove my '87 for many years that way.....never had a problem but I would've been happier with a more powerful alternator.

Some guys install a more powerful alternator...GM/ AC Delco usually....but it isn't an absolute necessity.

Cheers
DD

 

Thanks for your help.
Now to tackle a slow starter.

Cheers,
George