Alternator going bad?

[WVZR-1]

Originally Posted by -=Jeff=-

OK, get down to 11 volts when at 5k rpm

Below that rpm it is high 12s, I will data log to a file next time

You do seem to have issues either with the alternator or gauges! The load test is the only check and done on the vehicle. It could be the exciter wire OR maybe even a belt slip. I believe without looking you should be able to apply manual tension at the tensioner while running and see if that improves the charge rate.

LOAD TEST ON CAR - A little math and you'll know. All else is foolishness. You could do numerous replacements and until properly diagnosed still have issues.

[scottfab]

There is simply no need to do any kind of load test if the V on the battery is not right at idle. You can stop right there.
A load test is only indicated if at least 14V or greater is not seen at the
bat at idle. Also load tests don't need a carbon pile or a DVM.
A simple nicrom (nickle chromium wire) and analog gauge is fine.
Harbor Freight sells them.
Not belt slipping either unless you're hearing load squeaking.
Squealing was not mentioned.

Do the easy things first. V right at the battery at idle.
Sadly, based on experience it does sound like alternator.
Yet, doing due diligence is suggested.

[WVZR-1]

Originally Posted by scottfab

Not belt slipping either unless you're hearing load squeaking.
Squealing was not mentioned.

Doesn't need to "squeal"!

[scottfab]

Originally Posted by WVZR-1

Doesn't need to "squeal"!

I suppose that could be true, however if the the tensioner pulley has failed or is weak I'd expect the power steering to show significant lose of power and that is plain scary (been there).
Sure hope it is something simple like a loose belt for his sake.
Much easier to deal with.

[WVZR-1]

Originally Posted by scottfab

I suppose that could be true, however if the the tensioner pulley has failed or is weak I'd expect the power steering to show significant lose of power and that is plain scary (been there).
Sure hope it is something simple like a loose belt for his sake.
Much easier to deal with.

The spring in the tensioner fails/weakens and the arm then just flutters along at higher RPM's and the pulley isn't able to maintain a consistent tension on the belt. I believe that the relationship of the alternator pulley to the tensioner and the lesser diameter of the alternator pulley would be more suspect than the much larger diameter of the P/S pulley and it's relationship to the tensioner.

If the number he's posted are "factual" then there's certainly every indication that there's electrical system issues. He mentioned a "spare" isn't a bad idea - well it is when you unbox the spare months after the buy and it's a DUD in the box. I believe that with the price of the parts and the simplicity of the OE/GM unit if I had an OE/GM unit on it I'd much rather a repair than an off the shelf reman from Joe, John, Jim or Frank!

The connector at the alternator is as likely a candidate for failure as anything internal on the unit maybe.

[-=Jeff=-]

tensioner is new(er) maybe 3K miles.. I NEED to drive it with my datalogger on it to verify the data. when I drove it yesterday, I saw the gauge fluctuate. when I drove it a second time, I used my datalogger but I did not record, just viewed the data, that is when i saw it fall to the 11v mark.. the Alternator was last replaced in Jan 2010.. it was an AC Delco purchased @ Rock Auto..

I will check connections, and log data when driving the car and I will look for my old alternator as well.. I will keep an eye on it, like I said cruising around town it seems fine, it just seems to be an odd occurrence and i was just looking for some actual info as to IF the alternator could be the cause..

thanks for all the info so far

[scottfab]

Originally Posted by WVZR-1

The spring in the tensioner fails/weakens and the arm then just flutters along at higher RPM's and the pulley isn't able to maintain a consistent tension on the belt. I believe that the relationship of the alternator pulley to the tensioner and the lesser diameter of the alternator pulley would be more suspect than the much larger diameter of the P/S pulley and it's relationship to the tensioner.

If the number he's posted are "factual" then there's certainly every indication that there's electrical system issues. He mentioned a "spare" isn't a bad idea - well it is when you unbox the spare months after the buy and it's a DUD in the box. I believe that with the price of the parts and the simplicity of the OE/GM unit if I had an OE/GM unit on it I'd much rather a repair than an off the shelf reman from Joe, John, Jim or Frank!

The connector at the alternator is as likely a candidate for failure as anything internal on the unit maybe.

Well, while we're speculating and until we hear the actual verdict of what it is, I have to say:
1. I've had a "weak spring" in the tensioner pulley. It had no effect on the alternator. The power steering would be the first heads up AND it squealed big time.
2. I've had an alternator failure which exhibited this (his) same symptom. It was not a loose field winding lead.
3. I keep spares of most major components. Not a bad way to go at all especially given what prices of components are doing.

[-=Jeff=-]

I might have my OE Alternator I replaced in 2010, I am debating on rebuilding it

[WVZR-1]

Jeff - I mentioned the load test and I used the term "EVALUATE" in my first post and that was only because of the numbers you posted. The rest of the thread is maybe of little value but with 25 year old wiring I can't imagine why an "evaluation" wouldn't be wise. Here's a Delco/Remy (NOT ACD) newsletter from 2013 that's quite basic for all the load tests. It's the way it's been done for years when a complete diagnosis was desired or by fleets, municipalities and others that concern themselves with maintenance. A quality electrical repair shop does the same to "evaluate" unless there's obvious issues.

I would think a read of the newsletter might be of interest. The procedures in this read are quite basic:

http://www.delcoremy.com/Delco-Remy-...myConnect.aspx

There's also instances where excessive loads and the older/lower output alternators do precisely what you mention yours doing. Replacement with higher amperage output alternators has generally been a correction in those cases.

I believe the CS144 can be built to as high as 200 AMP configurations.

[-=Jeff=-]

WV thanks,

Yes I will evaluate the car and wiring, but I am also looking for at options (parallel tasks) instead if waiting until I can confirm the issue, I was researching what I can do for the alternator, I am quite sure the OEM output is limited especially with my aftermarket stereo. Hopefully will get time to look it over