New Alternator acts weird, and barely charges battery.

[MalibuHacon]

Since the day i got my 1980 malibu classic about 4 months ago i've been having problem with the alternator not charging properly, it charged very bad, only good when the car was on choke... i replaced my battery a few months ago because a cell or two was bad, i didn't change much.. anyways, i finally got around to just replacing my alternator, from a 55a to a 63 amp, rebuild remy alternator. (last week)

My new alternator acts even weired and worse than my old one, sometimes it will charge very well, 14,8V and will charge at more than 13V even with lights and accessories on. but most of the times it will not charge at more than 12,3 or nothing at all, and it will usually charge less if i rev the engine. The charging drops quickly if it somehow charges good right after engine has been started, when i turn on accessories the charging will drop down to 12,3 and i will not be able to get it up again. Sometimes when the alternator decides to charge it wil drop quickly when you rev the engine, and the sometimes build up again.

It charges so bad that i have to charge the car up with a battery charger a couple times a week

When you take of the plug with a red and brown wire it will start to charge really good when you put it in, and the drop after a few seconds down to 12,3 11,9, etc... I was told this plug had some significance in charging, and that some cars have an alternator light? I have not seen this light in my car before, i have 4 lights: (choke, brake, seat belts, high beam) and i also have the optional dash with the volt meter which seem to work (its of by a volt or two) but it seemingly shows accurate (13 when charging is good, but mostly around 10) ...
Does anyone know what is wrong, or how i might further diagnose this problem and fix it?
(I also replaced my starter motor recently)
Thank you

 

[Ribbedroof]

For starters, I would move the battery ground cable from the alt bracket to either the engine block or head. Ensure you have a ground strap from engine to car body...this is usually located at the back of the driver's side valve cover and screwed to the firewall.

 

[MalibuHacon]

I believe i have hat ground strap from engine to car body..
The battery has several grounds, two that goes from negative to the body at two different locations, + the one that sits on top of the alternator bracket

 

[565bbchevy]

It sounds like the power wire to excite the alternator is intermittent at best, a 1 wire alternator would have been a better replacement choice for the issues you were already having since they are self exciting.

 

[MalibuHacon]

What are my options? What do you mean by intermittent? is the "power wire" the brown one? I can probably replace the alternator again, deliver the old one back, would a 1 wire alternator cost the same?

 

[Ribbedroof]

The ground at the alt bracket is common for making poor contact. Given the rusty state of the removed alt, I still suggest moving it to the engine itself.

Not a fan of one wire alts, the OEs used a load sensing alt for a reason. That however is a personal choice and many people use a 1 wire setup.

 

[MalibuHacon]

But how does the ground have anything to do with amount of voltage the Alternator is putting out, and why does it put out good voltage when removing the plug and putting it back on again. And how can I make a ground on the block? where would i place it, is there anyway to test this theory?

 

[Ribbedroof]

Because the ground path is an integral part of the circuit. Intermittent ground = intermittent charge

I would not "assume" that the wiring and/or connections on a 36 year old car are good, without verifying it for myself. Ground from battery needs to go to a good clean bare metal point. I know GM ran it that way, but they were counting on the conductivity of the tapping screw into the painted bracket. Three decades later, quite probable there is corrosion there, even if the screw has been recently removed and replaced.

I would say about 90% of the time when we run into electrical problems in cars, it's a ground issue.

Can the place you sourced the alernator from test it off the car? Parts stores here in the USA can and do, to verify/eliminate replacing "defective" parts that are actually good.

Also, I would never advise connecting/disconnecting electrical components while the engine is running. Voltage spikes are not friendly to this stuff

 

[MalibuHacon]

Yes i am aware of this, i found several gremlins in the electrical, i will try to clean the surface of the ground and get some more eyes on this as soon as I can. However I have had several people look at it... tested the battery, grounds etc.

 

[Ribbedroof]

If all the grounds and the alternator itself check out good, then I agree that there is a problem in the brown wire.

Cars with the gauge package as original equipment do not have an alt lamp. The brown wire changes to a brown with white stripe wire at the bulkhead connector under the brake booster. The brn/wht wire originates at the ignition switch (powered in "run" , terminal 3) on top of the steering column.

Cars without the gauge package had a brown wire that remained brown at the bulkhead connector and went to the alt indicator lamp.

IF the car had the gauge package added, and the brown wire was not connected to the ign switch, there would be a problem with exciting the alternator, resulting in charging issues.

It looks like the car came with the gauge package, OR somebody went to the extent to collect the right dash bezel, etc to make it look original.