Alternator weak?

[spyerx]

As my severe OCD continues to 'get current' all the maintenance on my recent acquisition, I suspected the alternator (original 89) may be weak due to some noise, very, very slight that will come from it when all accessories are turned on.

Plugged in an eBay cigarette lighter volt meter (i've not measured at the battery, will do that today) and here is what I've observed. Note battery is brand new and I have not had any issues starting car or with charging....yet. Belt is brand new and adjusted correctly.

Car in accessory position, not running: 12.6v
Car running and idle, no accessories/electrical on but engine: 14v
Driving around with no accessories/electrical on: 14v
Turn on AC, rear defroster, fresh air fan, radio, fog lights, etc: 12.5v
Turn all that off, goes back to 14v.

Seems to me regulator is OK, but alternator is having a hard time once the load is kicked up.

Thoughts?

Any suggestions for a rebuild service in LA/OC area?

[Joe Bob]

Your alt is probably fine......a load test might ID an issue.

But my experience is that your AC has some issues. Dirty grounds, compressor about to seize etc.

[spyerx]

I'm hesitant to pull the alternator to bring it in to get tested. Those jobs always turn into one thing leads to another for me!

AC works really good on the car (keeping in mind I'm in socal like you and it's not very warm here), no odd noises, sounds when turning on, etc.

FWIW not turning on the AC sees similar drop to about 12.5...

I'll keep an eye on it.

[universeman]

My running voltage is also 14v but I have not tested it with load to see the drop.
If it's not making noise and is giving you a stable 14v at idle/run - I think it's OK.

[Joe Bob]

You don't have to pull the alternator for a load test.

Since the AC is the source of the voltage drop, stop by an AC shop for a diagnosis. Be advised, 911 AC systems would have to improve before they rate as just sucking....most are after market, and the companies are dust.

Germans don't have hot weather......

[spyerx]

Originally Posted by Joe Bob

You don't have to pull the alternator for a load test.

Since the AC is the source of the voltage drop, stop by an AC shop for a diagnosis. Be advised, 911 AC systems would have to improve before they rate as just sucking....most are after market, and the companies are dust.

Germans don't have hot weather......

I think you misread my post. AC is not the cause of the voltage drop. I can turn accessories on one after another and the voltage will drop. The AC drops it maybe .1v, turning on rear defroster drops like .4v. Its no greater or different than any other accessory. I'm not saying the AC is great, but, it's tolerable for me and blows cold when driving around.

[Joe Bob]

Get a real volt meter, those eBay meters suck at best. If you are a DIY guy, get a Fluke. Hook it to the battery terminals, actuate accessories......cheap way to find the biggest pull.

If you can maintain 12.5+ whiel running lights, ac, the electric windows, the GF's vibrator....it ain't that bad. When you drop to 11, that IS bad.....

If you are in OC CA, I will loan you a meter.

[spyerx]

I've a fluke meter. :-)
The $4 eBay one is actually right on with it too (surprisingly).
The cheapy just made it easy to see while driving plugged into the cigarette lighter.

[T77911S]

you really cant tell.
have the alt rebuilt by a shop.

[grizzfan]

Joe Bob's the expert and I agree with him that your voltages are appropriate. 14v to 14.5v is just about right when driving around.

Tom

[manbridge 74]

Rev it up to around 2500rpm when turning on all accessories. Voltage should be close to your 14v at idle.

[wwest]

Measure the voltage across the battery or the fuse panel in the engine compartment then report back.

[Porboynz]

Originally Posted by wwest

Measure the voltage across the battery or the fuse panel in the engine compartment then report back.

Good advice, measure at the battery itself. The feed to the cig lighter is subject to voltage drops as all the loads are added to the ignition feed wire. Alternators are typically good, or not, rarely in between.

[spyerx]

thanks all, will get a measure this week across the battery. sounds like preliminary assessment is alternator is ok...

[rick-l]

Originally Posted by Porboynz

Alternators are typically good, or not, rarely in between.

I'd agree except this is one of those needlessly complicated alternators.

Valeo designed this alternator as two separate (60 degree shifted) three phase windings hence the 14 diodes (17 counting the ones for the regulator). You can lose half the capacity and never know it since the second windings are not tied to the warning light.

Simplest to troubleshoot is to test all the diodes. If you had a big current probe you could look at the current pulses coming out of the alternator.

[Porboynz]

Originally Posted by rick-l

I'd agree except this is one of those needlessly complicated alternators.

Valeo designed this alternator as two separate (60 degree shifted) three phase windings hence the 14 diodes (17 counting the ones for the regulator). You can lose half the capacity and never know it since the second windings are not tied to the warning light.

Simplest to troubleshoot is to test all the diodes. If you had a big current probe you could look at the current pulses coming out of the alternator.

Live and learn, still the voltage at the battery is a simple first check point. The other method would be a hi current test meter to monitor current direction and amps. In the good old days I relied on the headlamps getting brighter when I revved the engine from idle to prove a functional alternator/generator, now on the basis that you can never have enough tools I have a clamp meter that works on AC or DC (expensive) plus an older current shunt ammeter (cheap).

[T77911S]

stop wasting your time. if you had 12.5v with acc's on then
have it tested and rebuilt.

[mysocal911]

Originally Posted by rick-l

Valeo designed this alternator as two separate (60 degree shifted) three phase windings hence the 14 diodes (17 counting the ones for the regulator).

All automotive alternators, i.e. <= 150, amps are designed this way.

Originally Posted by rick-l

Simplest to troubleshoot is to test all the diodes. If you had a big current probe you could look at the current pulses coming out of the alternator.

Maybe have the OP first clean and properly tighten all alternator connections:
1. at the alt itself (the connector should be fully cleaned & soldered)
2. at the starter motor
3. at the battery

[Porboynz]

Originally Posted by T77911S

stop wasting your time. if you had 12.5v with acc's on then
have it tested and rebuilt.

Where is the fun/learning in that? It may come to a rebuild but a few simple voltage and continuity checks may prove otherwise. Or at least prove its the alternator for sure.

[Ronnie's.930]

Originally Posted by T77911S

stop wasting your time. if you had 12.5v with acc's on then
have it tested and rebuilt.

Interesting, as I consider 12.5v measured at the battery, engine running at 1K rpm, and all accessories on (including a/c, foglights, etc.) to be of no cause for concern.