No charge, no speedo

Spdloader wrote:
>>Well, if it's not the battery mopping up all the amps til the fuse pops,
>>then it must be a short to ground.
>
>
> The battery tests fine with an AVR, that's all I have to test with, but it
> should be sufficient.
>
>
>>Have you tried it with the high current stuff (headlights etc) on and
>>then measure the volts as the revs are raised?
>
>
> Yes, revving the engine to 2000rpm with headlights, a/c, fan, and rear
> defrost, voltage went off the scale, and the fuse popped.
> It was a little slower, about 5 seconds.

Yeah, anything that's a short to ground should cause the voltage reading
to DROP, not jump up off the scale... that's pretty much guaranteed a
bad regulator, or something connected to the regulator (does it tie into
the car's computer anywhere??)

What year car is this again?

> Yeah, anything that's a short to ground should cause the voltage reading
> to DROP, not jump up off the scale... that's pretty much guaranteed a bad
> regulator, or something connected to the regulator (does it tie into the
> car's computer anywhere??)

There is a green connector with multiple wires. It does appear to tie in to
the vehicle computer.
>
> What year car is this again?

It's a 1998.

Spdloader

"Matt Ion" > wrote in message
news:JxSqg.122430$iF6.756@pd7tw2no...
> Spdloader wrote:
> >>Well, if it's not the battery mopping up all the amps til the fuse
pops,
> >>then it must be a short to ground.
> >
> >
> > The battery tests fine with an AVR, that's all I have to test with,
but it
> > should be sufficient.
> >
> >
> >>Have you tried it with the high current stuff (headlights etc) on and
> >>then measure the volts as the revs are raised?
> >
> >
> > Yes, revving the engine to 2000rpm with headlights, a/c, fan, and rear
> > defrost, voltage went off the scale, and the fuse popped.
> > It was a little slower, about 5 seconds.
>
> Yeah, anything that's a short to ground should cause the voltage reading
> to DROP, not jump up off the scale... that's pretty much guaranteed a
> bad regulator, or something connected to the regulator (does it tie into
> the car's computer anywhere??)

On your first point, it may not be possible to see the difference between
the
'short' (if there is one) coming on and the fuse popping. Both will see
the
voltage fall away.

On the latter point, I believe there is a compensatory signal applied from
the ECU when a heavy load item is switched on. It should be possible to
hear the engine load change when the headlights are switched off again
but revs shouldn't change.

It sure is a puzzle.

--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro.org.uk/ Wessex Astro Society's Website
Dorset UK Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

"> On the latter point, I believe there is a compensatory signal applied
from
> the ECU when a heavy load item is switched on. It should be possible to
> hear the engine load change when the headlights are switched off again
> but revs shouldn't change.
>
> It sure is a puzzle.
>

Yes, at idle, there was a noticeable change in engine load while switching
on the electrics, and alternator output changed to meet the requirement, but
once the throttle was "tweaked", the fuse popped, and the engine note
changed back.

The new alternator won't be in until tomorrow (Thurs) afternoon, so, another
day to over analyze this, I"m afraid.

Spdloader

"Spdloader" > wrote in message
m...
>
> "> On the latter point, I believe there is a compensatory signal applied
> from
> > the ECU when a heavy load item is switched on. It should be possible
to
> > hear the engine load change when the headlights are switched off again
> > but revs shouldn't change.
> >
> > It sure is a puzzle.
> >
>
> Yes, at idle, there was a noticeable change in engine load while
switching
> on the electrics, and alternator output changed to meet the requirement,
but
> once the throttle was "tweaked", the fuse popped, and the engine note
> changed back.
>
> The new alternator won't be in until tomorrow (Thurs) afternoon, so,
another
> day to over analyze this, I"m afraid.

I don't suppose you've tried a substitute battery on the system?


--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro.org.uk/ Wessex Astro Society's Website
Dorset UK Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

>> Yes, at idle, there was a noticeable change in engine load while
> switching
>> on the electrics, and alternator output changed to meet the requirement,
> but
>> once the throttle was "tweaked", the fuse popped, and the engine note
>> changed back.
>>
>> The new alternator won't be in until tomorrow (Thurs) afternoon, so,
> another
>> day to over analyze this, I"m afraid.
>
> I don't suppose you've tried a substitute battery on the system?
>
>

No. I don't have one at my disposal, but disconnecting the battery
completely had no effect on the problem, so I ruled it out.

Spdloader

Graham W wrote:

>>>>Have you tried it with the high current stuff (headlights etc) on and
>>>>then measure the volts as the revs are raised?
>>>
>>>
>>>Yes, revving the engine to 2000rpm with headlights, a/c, fan, and rear
>>>defrost, voltage went off the scale, and the fuse popped.
>>>It was a little slower, about 5 seconds.
>>
>>Yeah, anything that's a short to ground should cause the voltage reading
>>to DROP, not jump up off the scale... that's pretty much guaranteed a
>>bad regulator, or something connected to the regulator (does it tie into
>>the car's computer anywhere??)
>
>
> On your first point, it may not be possible to see the difference between
> the 'short' (if there is one) coming on and the fuse popping. Both will
> see the voltage fall away.

No, but either way, you still wouldn't see the voltage spike UP

> On the latter point, I believe there is a compensatory signal applied from
> the ECU when a heavy load item is switched on. It should be possible to
> hear the engine load change when the headlights are switched off again
> but revs shouldn't change.

I found an online manual for '95-'97 Civics... the wiring diagram there
shows a connection from the ECU to one terminal of the regulator...
without an actual schematic of what's happening inside the regulator
module, it's impossible to say for sure... the ECU lead ties with one
side of the regulator to the "low" side of the field coil, so it appears
it's entirely possible that a bad signal from the ECU, or even a short
in the ECU connection (either to power or ground, the latter is more
likely) could cause the regulator output to spike. That would at least
explain why the problem persists across three different alternators.

> It sure is a puzzle.

I love a challenge

Spdloader wrote:
> "> On the latter point, I believe there is a compensatory signal applied
> from
>
>>the ECU when a heavy load item is switched on. It should be possible to
>>hear the engine load change when the headlights are switched off again
>>but revs shouldn't change.
>>
>>It sure is a puzzle.
>>
>
>
> Yes, at idle, there was a noticeable change in engine load while switching
> on the electrics, and alternator output changed to meet the requirement, but
> once the throttle was "tweaked", the fuse popped, and the engine note
> changed back.
>
> The new alternator won't be in until tomorrow (Thurs) afternoon, so, another
> day to over analyze this, I"m afraid.

We may be on to something with the ECU link... wonder how hard it would
be to grab another one from a wrecker and plug it in, see if that fixes
things? Hmmm... or... I wonder if a diagnostic analyzer hooked to the
ECU would show anything anomalous?

In article >,
"Spdloader" > wrote:

> With the fuse replaced, at idle, the new alternator charges 13.9v, as soon
> as you rev the motor the tiniest bit, the alt/spd fuse blows.
>
> I'm guessing, I've got yet another bad alternator.
>
> Spdloader

It sounds like you have the output and regulator wires mixed up. The
alternator's regulator should draw more power at idle and never blow a
fuse.

"Kevin McMurtrie" > wrote in message
...
> In article >,
> "Spdloader" > wrote:
>
>> With the fuse replaced, at idle, the new alternator charges 13.9v, as
>> soon
>> as you rev the motor the tiniest bit, the alt/spd fuse blows.
>>
>> I'm guessing, I've got yet another bad alternator.
>>
>> Spdloader
>
> It sounds like you have the output and regulator wires mixed up. The
> alternator's regulator should draw more power at idle and never blow a
> fuse.

Um, nope, sure don't. Didn't read the whole thread, did ya?

Spdloader