'97 Accord swinging overcharge

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I have a '97 Accord in the shop that will swing from 14V to 18V, back and forth, over the course of 5-8 seconds. When the voltage spikes the battery light and several other lights on the dash (SRS, ABS, all the door-open indicators) come on. After several minutes it seems to stabilize but the thing usually dies and refuses to restart before that happens. Ideas?
 
K. I'd not yet seen one act this way, but I knew it had to have something to do with the regulator - just didn't want to throw an alternator on it (unless the VR can be replaced separate?) and it be the PCM or something giving a bad signal to the alt. - if the system even works that way. Having multiple small wires running to the alternator I wasn't going to rule out that the PCM commands it.
 
The regulator is replaceable but cost a fortune. It doesn't matter if the ecm is triggering it or not it shouldn't be putting out 18v, that kind of voltage can do damage. I would go with a new Bosch one from RA.
 
Replace the alternator before it can do more damage.

Some places have local alternator/starter shop that can get you better alternator and faster.
 
For sure check all connections but back in the day in the field we use to pop the battery cable to check the alternator (it didn't work on generators and they needed + input), if it continued to run the unit was working if it died it wasn't.
Do not do this today! The point is even when the cable was removed the alternator would still regulate not spin up to 18V. I am surprised this car hasn't burned out all the bulbs in the car.
 
Originally Posted By: Trav
For sure check all connections but back in the day in the field we use to pop the battery cable to check the alternator (it didn't work on generators and they needed + input), if it continued to run the unit was working if it died it wasn't.
Do not do this today! The point is even when the cable was removed the alternator would still regulate not spin up to 18V. I am surprised this car hasn't burned out all the bulbs in the car.


Disconnect alternator? My electrical system repair textbook (back in the day) said never to do this as high uncontrolled voltage would result with nothing to adsorb it. Was that book wrong? We used to do a very quick field test of alternator by holding a screwdriver to the rear bearing housing- if it was pulled in by the magnetic field, it was producing at least some output.
 
Course the book isn't wrong its a dirty way to do it but guys did it anyway, back in those days cars used mechanical regulators and nothing electronic so nothing happened for the couple of seconds it was off.
Screwdriver on the rear bearing worked also as you say to at least determine if it was working.
 
I believe if there is a large voltage drop on the - / body part of the voltage regulator, the voltage value can rise.
 
It does slightly with the old mechanical regulators but I never saw 18+v, as I said for momentary removal no harm done on those systems.
 
the common denso regulator is $15 on ebay and comes with a brush set.
i changed one in the car in 10 minutes on a 99 accord.
sounds like thats what is wrong with the op's unit.
mine was not sealed right at the factory and when a rather large family of carpenter ants colonised the car the washing to get rid of them killed the reg.
btw if the ground reference is poor the reg will respond with higher output.
so check that first.but its a cheap easy fix on the car.
regulator ebay
Originally Posted By: Trav
The regulator is replaceable but cost a fortune. It doesn't matter if the ecm is triggering it or not it shouldn't be putting out 18v, that kind of voltage can do damage. I would go with a new Bosch one from RA.
 
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Solved. After much head banging and talking to the owner (who thought the problem had persisted since before the alternator was changed the last time with a $75 Ebay unit) and his nephew who said he thought different, I put a Napa reman on it and all was good.

Gotta say, the little car ran and drove real good for 323K.
 
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