lol you guys are killing me!
haven't had a chance to test at the battery yet

Why replace or rebuild if it is not broken? If it is handling the load of all the accessories at idle and not drawing down the battery the alternator is fine. It is not producing its rated voltage at idle, and you dont drive at idle. That alternator will put out the exact same numbers after a rebuild.
It is working exactly as advertised, leave it alone unless you have too much money in your pockets and need to waste some.

I'm deciding to post here rather than opening a new thread. Report and questions relate to the charging system in my 89 3.2. I recently added some AC components (two additional fans [they may be pulling ~6.5a each but I haven't measured or confirmed with the data sheet just info. on 10" Spal fan that looks the same) and I've been observing the voltage using a cigarette lighter volt meter. I checked the cig. meter readings compared to those at the battery terminals using my handheld meter. The differences are within 0.1v.

I noticed with the high beams on and "new" AC system running - at idle the volts were barely 13.0 maybe falling into the 12's at times. This got me curious regarding if my alternator is/was able to keep up with the new added load. Since the Valeo 90 amp, 14v alternator was original I pulled it and had it rebuilt locally. The brush tracks were very deep and could not be resurfaced so it was getting time for a rebuild in any case.

After testing with the rebuilt alternator I noticed not much of change so I decided to check the performance relative to two other 3.2L cars buddies have near here, here are the results:

I measured two other cars at different loads and engine speeds. Measurement across battery or cigarette lighter. All cars have Optima batteries.

My Car (89 3.2L) (RedTop 15 years old, 12.55V, rebuilt alt.) - High Beams+ = with aftermarket AC system on (two additional fans)
Car T (87 3.2L) - ( RedTop 12.16V, 1 year old rebuilt alt.)High Beams+ = no AC (track car)
Car P (88 3.2L) ( YellowTop 12.29V, original alt.) - High Beams+ = stock AC on




* when load turned off after High-Beams+ test volts returned to 14.11, 14.33 is with cold engine.

Current conclusion. My Car alternator may be close to not be keeping up due to additional fan load. Maybe I have a marginal ground connection? Not confirmed so far.

Given all this I have a few questions:
1 - How close am I to the limit of what this alternator can provide at idle or other engine rpm's e.g. 2000 to 3000? How do we know that? Is there a performance chart somewhere? Do we use a rule of thumb - e.g. if the rating is 90 amps don't go over 45amps for an extended period?
2 - What is a good way to measure the actual amps output by the alternator? E.g. insert a pair of wires between the alt. and two red wires connecting at the plus terminal on the alt. and install a shunt meter?
3 - What is different with a high performance 95amp (compared to 90amp) alternator? Our host sells one.
4 - What voltage should I maintain while driving? 12.6 or above? Some say it takes more than that to "start" a charge going.
5 - One idea I have is to install a switch to kill one of the Spal fans if needed if the volts fall below e.g. 13.0 volts - could be while driving at night with AC on.
6 - To check the ground does it make sense to run a wire outside the car from an engine bolt to the negative battery post? This assumes the wire from the alternator to the engine case bolt is good - I know the engine bolt/nut and alt. connection nut are tight.

Thanks for any ideas along with battery recommendations. I took my 15 year old Optima to Batteries Plus and they tested it and said it was working OK but is now low on CCA (610) compared to the 1000 actual when new. It could be time for a new battery.

Thanks.

All I read was "15-year-old battery"...

Have most forgotten that there're two cables from the alt in the back to battery in the front,
alt to the starter and from the starter to the battery. Also remember that those cable aren't perfect
conductors with zero resistance, and as such will drop the alt voltage as the system loads increase.

Reducing the voltage drops:
1. Solder the red wire connector at the alt (no only crimps).
2. Solder both red wire connectors at the starter.
3. Solder the red wire at the battery from the starter.

Make sure all connections are tight.

One can always measure the actual alt voltage at the alt by measuring the voltage at the alt light
(blue wire in gauge). The difference between voltage at the alt verses the battery is the result
of the load current and cable voltage drops.

The new Interstate battery is installed and working great. Voltages are very similar to what I had on the 15 year old Optima. The guy at the Interstate All Battery Center tested the old Optima - CCA is 710 vs 800 new. He concluded the old Optima was still a good battery.