Thread: Sporadic Alternator Output

I bought a 110 amp alternator from AZ last year and haven't had any issues until this winter. Sometimes (usually in the morning when it's really cold) the voltmeter will only show that I'm at 12V (sometimes less) when I'm idling. Then when I start driving the volts go up as the RPM's go up. Other mornings, the volt gauge says 14V+ and the alt seems to be putting out a ton.

I do have a stereo system with subs, etc, and sometimes the volts output seems affected by having the stereo on and sometimes it seems completely unaffected.

This issue has caused me to have to jump the car sometimes (the battery acts as if it's dead), but what's strange is that sometimes it starts right up without hesitating.

I'm sure the alternator is on it's way out, but I'm just curious if anything else could be causing this. The last time I had to replace the alternator, it would just never go above 12V as if I didn't even have an alternator. This is a little weirder. Could I have a weak alternator bearing or something?

Thanks for any help....

Floating short in the battery could do that.

Originally Posted by 01GTP

Floating short in the battery could do that.

Do you mean within the battery itself, or do you mean some external connection somewhere? If within the battery, how does that work/happen exactly?

I did suspect the battery at first because of the random bad starts I was having, but then when I saw the charging issues, I put my attention on the alternator.

On the other hand, this is the battery that was in the car when I purchased it and I've had the car for five years now so it could be on it's way out as well. Would you guys recommend replacing the battery first or the alternator first? Or do you have any other suggestions?

Piece of metal broke off in the battery and floats around then shorts out a cell when it contacts the electrodes.

Hmmmm. Interesting.

This morning was bad. It was like the alternator would only go up to 13.5V if you had your foot on the gas, but as soon as you took it off, it would drop down to 12V.

it actually depents on the load management of the car. If the Battery is discharged, the Alt will have a higher output.

ALSO if you are using high current devices, ( Fan on High Defroster, Etc, that can have a negative effect on the voltage output of the Alt and the health of the Battery at the given time. After the high current devices are turned off the Alt can charge the battery.

Its not Always a problem espically with a relatively new alt. Chances are if the battery was bad, you would see a higher output from the alt trying to replenish the battery to full state

Here's a question - where is the best place to get HO alternators? I checked AZ, Napa, and O'reilley's and they all max out at 110 amps...

I'm curious about this as well...i don't want flashy lights when i put my system in lol.

Would an alternator from a '98 Bonnie SSEI be a direct swap?

Hmmm. I might go to AZ and compare the two visually and see if there are any diff's. The bonnie alt's are 140 amp.

considered an alternator rewire?

Originally Posted by matt5112

Then buy quality amps and set your gains with a osc scope.

Quality amp? Everything i buy is alpine...id say alpine is pretty good quality and i leave the gain way down.

Has anyone ever swapped in a Bonneville alt? Are there any other sources for HO alternators?

Well, I tore out the alternator and took it to AZ to have it tested and everything tested out well. I was afraid that would happen, because the alt does behave half the time. I also checked out the Bonnie alt's and they seem to be completely different in terms of mounting design, so that was out. So as a hail mary I put in a new battery and new battery cable bolts and that didn't change anything.

So. Anyone have any ideas? Any idea as to where to get an HO alternator for these cars?

Anyone?

I'm tempted to just slap down the cash for an HO alternator (looks like you can get them on Amazon, JC Whitney, etc), but I'm not sure that will fix my problem. I've noticed the biggest issue is when I'm at idle. Once the RPM's go up then the volts go up as well. It's just that sometimes at idle, it drops to 12V or even 11V with the radio and everything OFF! I'm concerned that I might have the same problem with an HO alternator if it's just not spinning fast enough at idle, I dunno. I'm really kind of at a loss with this one. Help?