Re: Car has very high voltage
- From: Dave Allured <nospam@xxxxxxxxxx>
- Date: Thu, 03 Jan 2008 08:35:03 -0700
I posted bad advice, sorry. This part may be wrong:
"Excessive output voltage is ... caused by ... specifically the
alternator's field terminal shorted to the battery positive circuit".
No, it depends on the alternator. In some the field current is
regulated by adjusting the field terminal current to positive, in others
it's to ground. In some it's more complicated than either.
In any case it is possible that some kind of external short to any of
the external alternator terminals *might* increase the field current and
cause excessive output voltage. That is something that you *might* find
by inspection if you are lucky.
It is also possible that you got a second defective voltage regulator in
the replacement alternator, though that seems unlikely as Nomad pointed
out.
It is possible to test the alternator with only the positive and ground
connected to the car, but you must know exactly how to rig the other
terminals for this to be safe, and this depends on the circuit.
At this point I think you should either find a complete diagram for your
specific alternator circuit, carefully measure all terminals and
understand the results, or else get experienced assistance.
--Dave
Dave Allured wrote:
.
By any chance does your Corsica have an electric windshield heater? I
once worked on this wierd system where the alternater would be switched
over to the windshield and cranked up to as much as 70 volts. That may
have just been a Ford thing, though. Late 80's or early 90's I think.
Otherwise I concur with others about checking all connections in your
battery and charging circuit, especially ground straps.
Excessive output voltage is generally caused by a bad voltage regulator,
or specifically the alternator's field terminal shorted to the battery
positive circuit. I'm not sure if your alternator has an external field
terminal.
You might check inside the alternator connector(s) or the wiring harness
for visible shorts, stray wire strands, broken insulation, etc.
--Dave
J wrote:
I bought my 1994 Chevrolet Corsica brand new and it has no modifications.
The car is well taken care of, has a 6 cylinder engine with 155,000 miles,
is in excellent condition and has never given me any problems until now.
For the past few months the vehicle's electrical system intermittently
surges from 12 volts to 19 volts (according to my voltmeter) at random
times. When it surges up, a red light on the instrument panel that is shaped
like a battery comes on. When it drops back down to 12 volts the light goes
out.
When it surges up, my headlights get very bright and my heater blower speeds
up. I have replaced 4 headlight bulbs in as many months but nothing else has
blown out.
Sometimes the power surges up and down every few seconds, while at other
times I can drive for hours without it surging at all. I have never smelled
anything burning, nor have any of the fuses been warm to the touch when I
touched them.
It does surge more often at high RPM than low. However, it sometimes doesn't
seem to be affected by RPM. Sometimes it is fine until I accelerate at which
time it surges, while at other times it doesn't surge at all when I
accelerate.
I cannot find a pattern to this in regards to hitting bumps in the road,
temperature and humidity, etc. The only item of auxiliary equipment in the
car is a police scanner and I have verified that it is properly connected to
the vehicle's electrical system. None of these seem to be the cause.
Due to the fact that I am worried that the car will become damaged, I have
installed a brand new battery, alternator (that contains an internal voltage
regulator), and battery cables. I have made a visual inspection of the many
wires and cables under the hood and they all appear to be sound and in good
condition.
Will someone in this newsgroup please give me some advice on what to look
for? Thank you for the assistance.
- Follow-Ups:
- Re: Car has very high voltage
- From: Rodan
- Re: Car has very high voltage
- From: J
- Re: Car has very high voltage
- References:
- Car has very high voltage
- From: J
- Re: Car has very high voltage
- From: Dave Allured
- Car has very high voltage
- Prev by Date: Re: Honda Accord: Mile Decline
- Next by Date: Re: Stripping a parts car
- Previous by thread: Re: Car has very high voltage
- Next by thread: Re: Car has very high voltage
- Index(es):
Relevant Pages
|
