j.kenzie@sbcglobal.net

Thanks,
I will wait until next failure then measure and tap.
Dave

Mrmerlin

I would vote for worn brushes and a weak battery. the worn brushes are letting you know that the alternator isnt working all the time hence the low voltage indications ,

the alternator isnt meant to recharge the battery,
so your idea to go for a long drive to charge things back to where they should be isnt sound.
That said you could have had a long period of discharge due to the faulty solar charger seemingly keeping the battery topped up when in fact the battery was never getting any charge

So use a volt meter on the hot post to check voltages not the dash meter as it always reads low.
remove the regulator from the alternator and inspect the brushes, make sure to check the blue wire for continuity from the alt to the 14 pin connector also fit a hot post cover.

If the battery is low then charge it with a 6 amp charger for atleast 4 hours

j.kenzie@sbcglobal.net

Thanks Stan. I fixed the solar charger connection and get about 16 volts of output. After I charged the battery overnight on my 10 amp charger, the car seems to start and run fine, with no warning lights. If the alternator cannot maintain the charge, I assume the problem will repeat itself. Time will tell.
Dave

Landseer

Document isn't extremely clear, but based on this, and our experience with 86 model during alt fail and battery discharge (all warning lights come on and flash in case of 86), I think 84 problem is alt brushes on verge of failure.

j.kenzie@sbcglobal.net

That is a great document and very informative. I guess my question is: Can a good alternator fail to charge due to a discharged battery only supplying 10 volts? I am hoping not to rebuild alternator, but will if needed.
Thanks,
Dave

Landseer

Dave, they wear out. Even if you replace it with this 85% certain diagnosis and it turns out to be something else, you needed to replace it for reliability anyway.

You could put a Camaro alternator on it, ensure there is continuity from terminal 1 of 14 pin to alt little wire and be done with it. Or swap with Roger or others for a new or rebuilt unit.

(edit)

j.kenzie@sbcglobal.net

Thanks,
Mine is one of Carl's 200 amp alternators and is about 4 years old.

http://www.928motorsports.com/parts/alternators.php

I suspect it is easily rebuild-able.
Dave

Mrmerlin

I would check the brushes first

j.kenzie@sbcglobal.net

Update.
After charging my battery overnite, and connecting my solar battery maintainer, my car has worked perfectly for the past two weeks. I forgot to mention that when all my warning lights were on, my voltmeter showed only 10 volts. I thought it was due to the warning system not turning on that gauge, but maybe it was just the actual charge of the battery. Anyway since charging, the voltmeter reads normally and the car .
Thanks for everything,
Dave

j.kenzie@sbcglobal.net

I thought I would post an additional update. I went through my receipts and found out that my Interstate battery was 6 1/2 years old. I guess I got my money's worth, so I bought a new battery, also Interstate. My car has been performing perfectly since then.
Thanks for all the help.
Dave

j.kenzie@sbcglobal.net

Further update:
You guys are so smart!! My car started to do its all warning lights on thing and the voltmeter showing 10 volts. I verified 10 volts at the jump post while running (rough). Once again, charging my battery for a few hours made the car run normally without warning lights and voltage of 13+. I decided to pull the alternator and have it tested. It failed on voltage, current and something else that I forgot. Anyway I will have it rebuilt, because it is a high output unit with a lifetime "fix it for the cost of parts" warranty.
Your helpful input was appreciated, even tough I did not want to face the fact that my alternator was dying.
Thanks,
Dave

Mrmerlin

usually the brushes wear down ,
then the alternator stops charging all the time,
then the battery gets weak,
then the car is started with jumper cables, that can damage the diodes in the alternator,
then the alternator wont put out its rated power,
then the brushes wear more ,
then the alternator dies and the battery goes bad from running at a discharged rate.
Then your replacing the battery and trying to keep it charged with a bad alternator.

Ahh its a viscous cycle.

Bottom line whenever a low charge is indicated check the brushes first,
this one step can correct the rest from happening

Alan

There is no way that 10V at the battery battery (which is extremely low BTW) causes the alternator excitation not to work - here cause and effect are the other way around! You are lucky the car started at that voltage though, since the battery charge level was very low.

It was either an alternator internal (regulator) issue or an exciter connection issue. That it worked again was odd but it is always likely to recurr as an intermittent issues at least.

Alternators will usually self excite at sufficient RPM - if at initial idle they do not kick in - its likely the exiter circuit simply isn't hooked up - this will also mean the bulb check for the charging circuit will not illuminate - or it could still be the brushes, regulator or regulator diodes

Seems you needed a new ignition switch for other reasons - but that didn't cause this issue.

BTW 16V is much too high - test with a DMM? - if you are really running that high this is a major problem. You will prematurely age the ECU's and other brains and while your headlights will be very bright - they will also die very young...

You need to ensure the voltage never goes much over 14V...

Stan - I know you think different on this but an alternator can charge a discharged battery very well, very fast and the only thing likely to get damaged is the battery (due to a charge rate just too high & overtemp - esp at 16V!!!). I'd still recommend charging a dead battery on a medium current charger - but to protect the battery not the alternator (which I think will cope just fine)

When all the warning lights stay on its always an alternator issue of some kind (on '84 and up*) and the battery probably is getting no charge - so be careful - you can't ignore it for very long...

Alan

* BTW I was unaware of this change in behaviour - very good to know earlier cars were different in this respect thanks Landseer!

j.kenzie@sbcglobal.net

Thanks, Alan.
16V is the unloaded output of my solar charger. I never get more than 14V anywhere else in my system. I think this is an intermittent problem, and it looks like internal to the alternator. It is going in for rebuild today.
Dave

Alan

Dave - since you have one of Carl's 200A units how has the performance at hot idle been over the time you have had it?

I imagine you aren't too happy with the need for a rebuild after 4 years - but has it performed OK otherwise?

Do you have anything special installed that required the extra amps?

Alan