A reman I got from Autozone was putting around 13.4V at the alternator battery terminal and not charging the brand new red Optima. The one in my red car pust 14.6V. I took it back to Autozone and they tested it in a brand new test station they have and all tests passed. I still ordered an exchange. Could it be something else? Is that 13.4V too low? Tks

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Palm Beach Fieros
http://pbfieros.tripod.com

quote Originally posted by Alex4mula: A reman I got from Autozone was putting around 13.4V at the alternator battery terminal and not charging the brand new red Optima. The one in my red car pust 14.6V. I took it back to Autozone and they tested it in a brand new test station they have and all tests passed. I still ordered an exchange. Could it be something else? Is that 13.4V too low? Tks

I have an autozone reman and it puts out ~14.5 volts at the battery. Anything less than 14v and I would suspect a problem. If it's at 13.4v I wouldn't trust it to last too long. Next time I'm buying a new AC Delco unit.

On my parents 95 Buick Regal we had an alternator go bad, that would not allow the signal flasher to work, but passed the benchtest so it is possible that the alternator was bad.

I might suggest having the battery tested just in case.

(for warranty replacement they wanted us to pay for a in car test if the alternator passed we were supposed to pay for, which through Canadian Tire is quite ezpensive and we would have had to wait a few days for a booking to get it tested)

Our test was swapping alternators between my parents cars as they have the same engine and alternator, and this fixed the problem in the problem car, and requested an immediate exchange.

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1988 Fiero GT

http://www3.telus.net/1988_Fiero_GT/1988_FIERO_GT.html

Did you buy the cheapo Valuecraft alternator or the half-decent Duralast one? The Valuecraft alternators, the take a core, fix whatever is wrong with it, paint it, and put it in a new box. The Duralast alternators, they replace the internals and put them in a repainted core's case.

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1984 Fiero SE

Unless someone changed the criteria, an alternator ahould put out 13.8v nominally, that is under normal load. normal for most stock alternators on a car with no lights on, no accessories, and a good battery is 14.4 v at idle. Boats are usually spec'd at 14.4v nominal.
The real test in a car with no other equipment other than a fairly accurate voltmeter:
headlights on, high beams on, ac on, fan on full, all interior lights on, radio on (amplifiers off!) wipers on should be able to hold
13v at idle, and 13.8 at 2000rpm. if ti drops to 12v or less with the load on, the alternator is not putting out enough to keep the
battery charged, which is normally 13.2 volts for a healthy battery. (+-.2v)
Some cars are notorious for under sized alternators, those will always tend to pull down to 12v with everything on.
undersized is the hardest to see without full load. generally a bad alternator can exhibit normal at idle, and drop down to 12v with any real load, that's the problme most people without guages won;t see till the car dies on the road or won;t start after a trip.

If I remember correctly reving he engine didn't make any difference on the output. I do have an under drive pulley installed so that may make a difference at idle. Thanks all for the replies.

quote Originally posted by Alex4mula: If I remember correctly reving he engine didn't make any difference on the output. I do have an under drive pulley installed so that may make a difference at idle. Thanks all for the replies.

I put 2 a-z `s one of my 86`s that tested ok at their store, both where junk, got my $$$ back and went elsewhere--I think your good (real good) if its around or above 13.9...

I used Duralasts in mine for 7 years. One went bad (diode fried) and they exchanged it. It always put out 14.5 + volts all the time.

I have a Duralast in mine and it puts out 14.5
Don

13.8 Volts is the nominal voltage of a fully charged lead-acid battery. The alternator voltage has to be a bit higher than 13.8 otherwise the battery won't reach full charge.

With the engine idling and the headlights on, the alternator should be putting out over 14 volts. (I usually look for 14.2 V.. That's .4 Volts over 13.8.

Is this for your V8?
I dont know where it came from because it was in the car when I got it but my single wire alt puts out 14.5v with no load.
It drops to 13v with the lights and fan on. I also run an electric water pump.
You may need a bigger alt to keep up with all of the stock electrical parts and the electric water pump.

quote Originally posted by Jake_Dragon: Is this for your V8? I dont know where it came from because it was in the car when I got it but my single wire alt puts out 14.5v with no load. It drops to 13v with the lights and fan on. I also run an electric water pump. You may need a bigger alt to keep up with all of the stock electrical parts and the electric water pump.

Nope. The V8 one is fine even with my e-pump and amps. Tomorrow the replacement should arrive. Maybe Saturday I can install it and test it. Thanks all again

To answer the original question, 14.8 Volts.

(edit: The CS alternator output is nominally 14.8 Volts but it is temperature compensated and can be as low as 13.8 Volts at high temperatures. The SI type is usually 13.8 Volts but some are 14.0 or 14.2 Volts).

quote If you replace a sealed maintenance free battery in a GM car with a non-sealed lead-antimony or lead-antimony/calcium low maintenance battery, you will need to check the electrolyte levels more often. This is because GM sets their voltage regulators at higher charging voltage, 14.8 volts, to recharge the sealed maintenance free lead-calcium/calcium batteries, like the original AC Delco batteries. Pacific Power

If you use an non-sealed battery (edit: in a car designed for the sealed type), the electrolyte "fog" produced by over charging will also increase corrosion around the battery.

[This message has been edited by spark1 (edited 03-11-2006).]

quote Originally posted by Poncho Jim: 13.8 Volts is the nominal voltage of a fully charged lead-acid battery. The alternator voltage has to be a bit higher than 13.8 otherwise the battery won't reach full charge. With the engine idling and the headlights on, the alternator should be putting out over 14 volts. (I usually look for 14.2 V.. That's .4 Volts over 13.8.

You are wrong. (So was I) ,lead acid cells are 2.15 volts apiece, 6x2.15 =12.9 . this is just chemistry of a lead acid cell, nothing you can do changes it. and that is almost ideal conditions. A hot charged battery will read 13.8, but that voltage is not realistic. check it a day later, and a good battery will sit around 13 v.
Charging at higher than 14.5v heats the battery and causes all types of internal problems, like plate buckling, boiling out, opens, sulphation, etc. temperature also factors in to the charge rate. recommended for average temperatures, the specify around 2.3v / cell for standby charge, and 2.4v for cyclic charge. Car use is somewhere between the two types.
Car electrical systems are specced to be at 13.8v, this allows a reasonable charge rate for the battery. anything over that will tend to overcharge the battery, but that just shortens the life of the battery. In reality, anything over 13.8 an under 15v is within tolerances most batteries are designed for. GO check the service specs for checks for any car mfg. 13.8v plus a range usually - .5 to +1.0
There is also an internal resistance in each cell, so that also loweres the effective charge rate for the middle cells. notice boiled out batteries or batteries with opens/shorts tend to be in the end cells, not the middle.

I got the replacement and installed it today. No change. 13.4V at idle or at 4000 RPM. When I turn on all the electric accesories then it drops to 11.8-11.9V.
I measured the resistance of the wire from the alternator to the junction block and it was 17 ohms. I was expecting more 3 to 0.1 ohms. Not sure if that would make a difference. When I measure the voltage I put the probe at the alternator bolt.

The correct answer is....

14.7 Volts DC. Or bloody close to that. What you actually read on a volt meter is more complicated but if you are reading less than 14V at the battery with the car running you probably have wiring and/or alternator problems. Ohms on that gauge wiring should be almost nothing if you can measure it at all.

They call it a 12 volt system but thats not correct. A charged battery is about 12.6 volts after is sits a bit. The alternator specification is 14.7 Volts.

The 36 volt systems under research you sometimes still hear about actually charge at 48 volts.

[This message has been edited by theogre (edited 03-11-2006).]

Are you sure your resistance reading is correct? The alternator would not be capable of charging the battery if the resistance in the wire to the junction block was 17 Ohms.

quote Originally posted by Alex4mula: I got the replacement and installed it today. No change. 13.4V at idle or at 4000 RPM. When I turn on all the electric accesories then it drops to 11.8-11.9V. I measured the resistance of the wire from the alternator to the junction block and it was 17 ohms. I was expecting more 3 to 0.1 ohms. Not sure if that would make a difference. When I measure the voltage I put the probe at the alternator bolt.

double check that reading. also, that is a fusable link, it is 20 yrs old, and if it had a bad battery putting alot of load on it, welll..... you get the picture.......

Try putting the meter lead right on the alternator output to a good gorund on the - side. see if the voltage is goo there and bad at the junction. if it is, the your high resistance reading is correct, and you need to find where. Look at the junction block end, I believe it goes thru a factoy splice before the ring, and that is where it splices to the fusable link portion.

[This message has been edited by tjm4fun (edited 03-12-2006).]

As I mentioned above... The battery is a brand new Optima red top. The 13.4V reading is at the alternator terminal and not at the battery terminal. The 17 ohm resistance is from the bottom of the wire (disconnected) at the alternator to the junction block. I'll measure the wire on my other car and compare. Thanks all for the tips!

quote Originally posted by Alex4mula: As I mentioned above... The battery is a brand new Optima red top. The 13.4V reading is at the alternator terminal and not at the battery terminal. The 17 ohm resistance is from the bottom of the wire (disconnected) at the alternator to the junction block. I'll measure the wire on my other car and compare. Thanks all for the tips!

If you're only reading 13.4 at the alternator terminal then the alternator is not working correctly.

OK, lots of people have chimed in with their ideas about what the right voltage should be. Here's the real spec: with the battery charged and the engine running at 1800 RPM, the battery voltage should be between 13.8 and 14.2 volts - when measured with an accurate meter.

Wrong voltage at the alternator output can be two things...

1. The alternator is screwd up. Have it tested.
2. The wire that goes to the Sense terminal has problems. This wire is used to manage the output voltage.

I would strongly consider replacing most if not all the wiring to the alternator.

Also when you test the alternator output voltage... The wiring all has to be connected. If it's not you won't get a good reading. The SI series alternators are wired similar to the F type CS alternator shown in the CS alternator article in my cave. (I don't have anything that is specific to the SI. I think Sense is A and Lamp is B on the SI units.)