> From: Cory Carpenter <coryc@sequent.com>
> Has anyone ever seen the following charging-system symptoms --
> system works normally when the battery is fully charged and
> the total load is low, but if the battery drops below a certain level,
> or the load gets too high, the ammeter pops over to the "D" side of the
> dial, and things begin to get slow/dim
Yes, that's not uncommon in a system with a mechanical voltage regulator.
The charging rate of an alternator is controlled by varying the current in
the rotor, or "rotating field." With a mechanical regulator, this is done
simply with a resistor in series with the field and the battery for the
"low" charge rate, which causes the alternator to supply enough current for
the normal engine load plus provide a small charge to the battery. When
more charging is needed, a set of relay contacts shorts out either a portion
or all of the resistor, increasing the field current, which causes the
alternator to put out a "high" amount of current.
It could be that your regulator isn't switching to the "high" charge rate
properly. Because the alternator seems to be working at the low charge
rate, I don't think the problem is with the alternator.
> Additional information: The schematic shows two leads to
> the + terminal of the alternator, while mine has only one lead, with a
> second lead that's been disconnected from *something* tie-wrapped to the
> harness.
Ugh. Sounds like the dreaded PO syndrome! :-\ Actually, it sounds
like the alternator/regulator may have been replaced with something
non-original??
> Also, there's a lot of "bounce" in the ammeter needle when the
> system is charging, I assume from the mechanical regulator, although it
> doesn't seem to me that it should be opening and closing that much.
Yes, it is from the mechanical regulator, and yes, it does bounce around
a lot, especially with the undamped Jaeger gauges (on my TR4, anyway).
If the needle is bouncing around, tho, that seems to indicate that your
regulator *is* indeed working... (more later...)
> There's also an alternator *rely* that appears in the schematics, and
> which I *believe* I've located, next to the regulator, but the manual
> doesn't give any troubleshooting information on it, or even describe its
> function.
Hmmm. Got me on that one. I would guess that a relay associated with
the alternator would have something to do with a start up override
circuit or something.
> Thoughts I've had (aside from setting the car on fire):
> swap the relatively large alternator pulley currently installed for the
> smaller-diameter one that came with my replacement unit (hoping the higher
> shaft RPMs will increase the output);
I'm sure that the larger pulley was installed to reduce the load of the
charging system on the engine, to allow more of those ponies to get to the
rear wheels. The larger pulley itself could cause the symptoms you
describe (ammeter suddenly swinging to the "D" side under load), but I
wouldn't expect it to go very far "D" - if it does jump way over to the
"D" side, I would expect that maybe the belt/pulley is slipping under load??
Check this out very carefully before doing anything else serious, like:
> Hook up the "unused" wire of unknown purpose and hope that it magically
> fixes the problem (risky... I tried this with a vacuum tap one time on
> the first vehicle I ever owned, and thus learned how to rebuild a
> carburettor);
And don't do it here either, unless you've figured out for sure what this
"extra" wire is for. (I'm assuming that this charging system worked once
upon a time?)
> let the car sulk in the garage for awhile longer, hoping it will see the
> error of its ways and decide to behave itself.
It would be worth a try, but, then again, if this worked, my TR4 would have
fixed all of it's problems itself by now! :^)
Good luck!
Pat Vilbrandt John Fluke Mfg. Co., Inc. Everett, Washington USA
UUCP: pwv@tc.fluke.COM or: { uunet, uw-beaver, sun, microsoft }!fluke!pwv
ARPA: fluke!pwv@uw-beaver.ARPA
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