1982 Starlet electrical nightmare

I purchased this car used last year and have had constant problems such
as battery draining after a very short time unused, snapping of the
engine fuse disabling alternator, and car running after the key is
removed. I suspect some type of short but I don't know where. I have
replaced both battery and alternator to no avail. I fear these problems
will cause alternator and battery to deteriorate.

On 19 Feb 2006 11:58:48 -0800, "derek" <derek_sacerdote@yahoo.com>
wrote:
[color=blue]
>I purchased this car used last year and have had constant problems such
>as battery draining after a very short time unused, snapping of the
>engine fuse disabling alternator, and car running after the key is
>removed. I suspect some type of short but I don't know where. I have
>replaced both battery and alternator to no avail. I fear these problems
>will cause alternator and battery to deteriorate.[/color]

My first thought is the alternator has an internal problem like a
bad diode that intermittently partially grounds out (high resistance
ground) and drains the battery, or totally grounds and pops the
fusible link/main fuse - Have you had a rebuild installed since you
bought it? On an '82 it might be an external regulated alternator,
or a first generation with the internal regulator.

One of the Dealer Techs that hangs out here may have heard of this
one happening before - and on a 24 year old model, they're liable to
have seen it a lot. The run-on problem could be related to an
electrical back-feed from the alternator failure warning light circuit
through to the ignition coil, but that's just a wild guess.

(But a lot of my 'wild guesses' tend to be close to the mark.)

Note that I am NOT saying "That's the problem, Change it" but the
alternator is the first item to check with a voltmeter and ammeter to
see what is going on - and check it with an oscilloscope if you have
one.

The output waveform will be all funky on the scope if you have a bad
diode - the alternator internally puts out three-phase AC power that
is rectified by the diode stack into DC, and when you drop a phase the
bad "AC Ripple" on the output line is very obvious - if you only have
a voltmeter, you'll see several volts of measurable AC Voltage on the
output line. The AM Radio will probably be un-listenable from
alternator whine.

And get the battery load tested, and check the manufacturing date
code - if the battery is old enough to be out of warranty, change it.
They go bad just from old age, and the warranty date is just the
median failure time they're saying you'll get past. Bad batteries can
ruin good alternators, and bad alternators can kill good batteries.

WARNING: DO NOT try running the car with the battery disconnected
or that main fuse blown! Depending on the design of the circuit, some
alternators will go full-field wide open when there is no battery in
the circuit, and they can send well over the normal 13-15 VDC out to
the rest of the car (50 volts or more) which can and will fry lots of
expensive things. This is bad.

If you go get the alternator rebuilt on general principles, get a
proper rebuild done - new ball bearings, windings checked thoroughly,
new brushes, new diode rectifier stack and new regulator. They buy
the parts in bulk, so it isn't that expensive to do it right.

The chain 'Beauty Auto Parts Stores' send them out and the cheap
rebuild shops they use only clean the outside, change what they think
are the "bad" parts, toss 'em in a clean box and ship 'em back out...
They figure the "Lifetime Warranty" will cover the come-backs.

I had one bad afternoon when the alternator died away from home and
a Kr***n was the only parts store around, it took R&R-ing four
[expletives deleted] alternators in their parking lot to find one that
worked.

(But it was swap the alternator there or chance 50 miles home at
night running only on the battery, which would be dicey. And if you
stall an automatic with a dead battery, now you're in deep [stuff].)

--<< Bruce >>--

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

Thanks for the leads I will look into it. The alternators I use always
come from ebay rebuilder overstocks so I don't know their background.
This one has an internal regulator, as did the one I replaced. The
harness plug was missing, so I actually spliced the wires ( yellow,
blue, and white) color to color from alternator to harness. The battery
is a new deep cycle, since I have a tendency to run its charge out. Are
you saying that if I remove the warning light relay that will probably
stop the ignition problem?

On 21 Feb 2006 21:04:54 -0800, "derek" <derek_sacerdote@yahoo.com>
wrote:
[color=blue]
>Thanks for the leads I will look into it. The alternators I use always
>come from ebay rebuilder overstocks so I don't know their background.
>This one has an internal regulator, as did the one I replaced.[/color]

Only the people who did the work know whether it was done right, or
done cheap... I go to the shop and can stand there and watch them
work on mine, so I know. (But I usually go disappear for an hour or
two - there's an Electronics Surplus Store about a mile away.)
[color=blue]
>The harness plug was missing, so I actually spliced the wires ( yellow,
>blue, and white) color to color from alternator to harness. The battery
>is a new deep cycle, since I have a tendency to run its charge out.[/color]

Check your connections.
[color=blue]
> Are you saying that if I remove the warning light relay that will probably
>stop the ignition problem?[/color]

Hey, if the engine won't shut off, and you go pull the warning light
relay and the engine stops right now, that's where I'd start looking
for a backfeed or a stuck relay.

Or the wrong relay. There are a few odd automotive Bosch Cube style
relays that are DPST 'double break' with a common hot and two switched
legs, and they plug into the same socket as a SPDT - which could send
power where it isn't wanted. They build some relays with a
Counter-EMF diode across the coil or as an arc snubber across the
power contacts. And either the diode shorts, or you aren't supposed
to use one with a diode on that circuit, or you ARE supposed to have
the special relay and someone put in a plain one.

Never underestimate the stupidity of... ;-)

--<< Bruce >>--

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.