Gregory,
I'm going to have to tell you, you've got me stumped! Lets try a few things
and see what happens. First of all, have you tried unplugging the alternator
and running the car? If not, why don't you try that and see what happens. If
the problem goes away, it's most likely the alternator is the problem. If it
doesn't go away, we'll have to look elsewhere. Just pull the plug on the
back, and then drive the car as usuall (as long as the battery lasts, the car
will run just fine this way).
I really don't think you have a short, at least not as we normally think of
them. It would take a SERIOUS short to drop the battery voltage 4 or 5 volts,
and I think a short of that magnitude would soon identify itself -- smoke and
flames! I could be wrong, but that's what I think. I would be more inclined
to think you have an intermittant open circuit that is showing up as a
reduced voltage.
A few questions: You said the ammeter was wired in the main battery lead --
do you mean the big cable from the battery plus post to the solenoid?
On your Spitfire, is the ignition switch on the steering column? (I have a
TR6, remember, so I am not sure of these kind of things on the Spitfire)
> If I turn the car on, but don't start it, voltage drops below 8 (scale is 8
> to 16v)
> If I start the car, voltage "flutters" from 8v up to battery max. Max drops
> as the battery discharges. It takes about 2-3 hours of driving (no lights)
> for the battery to discharge.
> If I hook up the voltmeter directly to the battery (+ and -) I get the
> expected ~12v
When you say "If I hook up the voltmeter directly to the battery (+ and -) I
get the expected ~12v," do you mean under the same conditions as you are
getting the fluctuations? ie, with the engine running, you get a fluctuating
voltage with the VM connected to the large brown wire, but a full 12v if you
connect to the battery? There should never be more than a very minor voltage
difference between the two, unmeasurable on anything other than a very
precise VM. If that is the case, you might want to remove the ammeter and see
what happens. Just reconnect a large cable from the battery post to the
solenoid, with out the ammeter.
Let me know, and I'll see what I can come up with in the way of
troubleshooting via e-mail. We may have to try this and that and thus over a
few days before we get it fixed. I'm willing to try if you have the time.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://members.aol.com/danmas/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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