Ford 460 alternator output, how much is TOO much?

Joe Smith · #1 (**permalink**) 05-12-2002, 08:10 AM

After several years of less than stellar performance from my 460's alternator,
I had it re-wound to up the output last week. Before, I would typically see
about 12.5 to 13 volts max on my car's voltage meter at highway cruise speeds.

I am now seeeing 15.0 - 16.0 volts at cruise, and sometimes the needle is
buried in the red if my electric fan is turned off. I'm running an Optima gel
cell battery in my car. My question is this, am I harming my system / battery?
Short or "de-winding" my alternator or changing my pully geometry, what can
I do to make a more managable charge rate? For that matter, what is normal
for my alternator.....I'm assuming 14.5 volts is a nominal output.

Thanks in advance for any advice......

Jack21 · #2 (**permalink**) 05-12-2002, 04:24 PM

Yes you are harming your system, and frying your battery with a voltage output that high. First, double check that your battery is good, and you're not trying to charge a dead cell. Then, take your alternator back to your rewinder and have it redone. Or go to Summit and get a Powermaster replacement.

The amperage output is supposed to go up, but the charging voltage should stay in the 13.5 - 14.5 range.

Cobras don't have a lot of electrical needs. CD ignition, electric fan, e-code halogen headlights, even a sterio amp in the trunk. You don't need a 140 amp alternator to run this. I have a standard 63 amp Delco alt, and all the electrics work fine.

trudellt · #3 (**permalink**) 05-12-2002, 05:11 PM

Joe,

It sounds to me like it would be worth checking your regulator as well. (As I understnad it), in a properly operating system, the regulator monitors the battery voltage and adjusts the field on the alternator accordingly. My understanding is that even a 100-amp alternator is not too much (although it is a bit of a waste) since the regulator is controlling its output. Obviously a 100-amp alternator does not "force" 100-amps into a system, it is capable of that, however.

This is true for external or internal regulators - and even the self-exciting 1-wire alternators. They ALL have a regulator in some form or another to protect your battery (and electronics) from overcharging.

Jack21 gave you good advice. Don't run the system that way. At as little as 15V, I've read you could actually have Hydrogen outgassing. That's not funny.

Let us know what happens.

Jack21 · #4 (**permalink**) 05-12-2002, 06:42 PM

Joe, the assumption, perhaps incorrectly as stated above, is that the alternator is internally regulated. If you have an external regulator, the regulator, not the alternator is most likely at fault, and should be replaced.

I went with a Delco just because of problems like this which is typical of Fords. If you go with a Powermaster Ford replacement, it should be internally regulated.

Joe Smith · #5 (**permalink**) 05-12-2002, 07:19 PM

I'll check things out, and let you all know what I find.

Joe Smith

Mr.Fixit · #6 (**permalink**) 05-13-2002, 11:43 AM

If it's a regular 60-70's style ford alternator (or replacement) than it has an external regulator. This is what shuts off the alternator when the volts hit 14. That is your problem, the regulator is not turning off the alternator. Swap out regulators first, and be sure the rgulator is grounded to the chassis. This is usually done by bolting it to the inner fender on a steel car, you see the problem with a fiberglass car. Run a ground wire to the case of the regulator. There is very little need for a 100 amp alternator in a cobra. The regular 63 amp jobbers usually work just fine, if too little amps at idle with the fans on, than a 90 amp unit is great.

HighPlainsDrifter · #7 (**permalink**) 05-13-2002, 01:34 PM

Hi,
Before you do anything hasty,get a proper digital meter and measure the voltage, stock gauges are notorious for being out of whack.
Perry.

chopper · #8 (**permalink**) 05-13-2002, 08:13 PM

FWIW, HighPlainsDrifter has an excellent point. Check the voltage with a good quality voltmeter and verify that the system is really putting out what the dashboard voltmeter says before getting overly excited. If the battery is really seeing 16 volts, the voltage regulator is bad.

My car had an original "contactor" style Ford external voltage regulator installed when I bought it. The alternator took a dump one night and I pulled it off the following day to have it rebuilt. Just for kicks, I took the voltage regulator to the shop with me and had it tested; it was toast, too. The friendly repairman had both the original "contactor" style and a solid-state replacement which externally looks identical to the original unit (little black box about 2X3X2 inches which had the appropriate connector to plug into the wiring harness). I installed the solid state unit and haven't had any additional problems over the past five years. I'm reasonably sure any good alternator shop should have the solid state units available.

bran3b · #9 (**permalink**) 05-13-2002, 09:53 PM

Not to beat a dead horse, but I had similar symptoms with a poor ground on the regulator, and I caused major problems with my battery (also Optima). After a long drive I had overcharged to the point of causing the battery to expand and smoke. After running a ground to the Alternator body the power output went back to 14V.

xlr8or · #10 (**permalink**) 05-13-2002, 11:07 PM

Definitely go with the good meter and check it. When I put a new harness in my truck I also put in some new guages and was showing 14.5 at idle and just under 16 as soon as I touched the gas pedal. Checked with a good meter at the alternator and the fuse block and found out I was only getting about 13.2 at idle and 14.5 after that. Which is what it should be.

Also as a side note: I checked the guage and if you remove the light fixture I could see an adjuster block inside the guage. Tweaked that and now it reads what it should.

boxhead · #11 (**permalink**) 05-14-2002, 04:46 AM

1/ check actual alternator output with known good voltmeter.
2/ if your alternator has an internal regulator then check all earths from engine to chassis and chassis to battery.
3/ if your alternator is fitted with an external voltage regulator then check to make sure your regulator is earthed via its body
4/ if you have the external regulator then where is your voltmeter wired too? is it on the alternator output or the regulator output?
5/ make sure there is no resistance in the alternator body to battery negative circuit, (should be earthed through the earth harness and chassis harness)
6/ if all this is ok then it would seem you have a faulty regulator.

Joe Smith · #12 (**permalink**) 05-21-2002, 12:00 PM

Well, to make a long story "short" (pun intended) my car's previous
owner had incorrectly wired the alternator into the harness! After consulting
a Ford wiring schematic, and changing a few connections, it appears that
my problems are solved. She's charging on the money at all rpms now...

Thanks for all who gave great advice!

Jahred · #13 (**permalink**) 05-26-2002, 08:12 PM

Ok. So here I go again. I have an Optima battery in a Cobra just back on the road. The gauges are Autometer. Best I recollect, the alternator is Maqnum, I think probably 80 amps.

Was out on a long run today. Have been concerned cause the alt gauge ussually reads 16v or better. Got some major gassing from the Optima today.

Is the regulator in the battery on this thing? What happens with the gassing? Will it just blow the car up or me too? Presume there is risk of that sucker blowing? It was hissing for quite a while. There was a semi noxcious/sweet smell for a while and it took a while to figure out where it was coming from. There was some smoke or visable vapor coming from one of the terminals. I have a groud problem but the last guy I asked to have a look at it said it was properly grounded.

Any thoughts? Comments/observations appreciated.

Jahred · #14 (**permalink**) 05-27-2002, 06:26 PM

OK. Got her fixed. The info on this thread was very helpful. My alleged "ground" wire was totally fried. I wasn't sure just what I needed to do, but a few trips to the hardware store and I had a new wire run from the alternator to the regulator and then ran a second wire on the same string to the radiator where it was bolted to the chassis. First time I have seen under 14 volts since its been on the road. Another initiation "bug" beaten down. Thanks to those that provided some input on this thread.