holy volts batman!!

[67Fleet]

Got a new alternator today since my old one took a dump. Decided to get a 94amp from 84 Camaro. It seems like everything is working fine, I'm getting more charging than the previous one, and my voltmeter in the dash stays at just about 3/4 full when just off idle. My old alt would struggle to get the meter past the 1/2 way mark. I have a question though. I have a pretty lopy cam in my truck, so it idles rough. At idle my compressor for the airbags sometimes surges a little bit. Is this normal since my cam is causing the rough idle? I sure do have a lot more juice to the compressor than I did before. It fills the tanks faster now and is a bit louder. We tested the battery with a multi-meter and it read 15 volts at just off idle with my lights and the compressor running. If it's idling and I then turn my lights and the compressor on, the voltmeter in the dash moves to the right and shows higher voltage. Is all this normal?

[Longhorn Man]

Do you have a volt guage in the truck? What voltage is it reading?

I suspect you have an AMP guage. If it is charging clear over, then there is actually something wrong.
When you start the engine, it should raise a little, but only for a min or so, then it should drop to just a hair over center. Plus, your 15 volt reading on the battery, is entirely too high.
How did you wire this up?

[67Fleet]

Yeah, it's the stock Amp gauge. It never gets past the 3/4 mark. It doesn't go all the way to the right.

[Longhorn Man]

You are still overcharging. It should only be a hair above the center when running after a few min. And like I said... 15 is too many volts.

[67chevy2wd]

I agree 15v is way too high, I believe it should be around 13.5v tops. Does the alternator have an internal regulator? I really don't see how you could wire it wrong, if you hook up the #1 and #2 terminals on the alternator backwards won't the alt put out little to no amps? Now I have confused myself.

[ThatOneBlue67]

Could your alternator have come off of a Camaro that had a smalelr motor? Let's suppose the alternator cranks out more juice with more rotations. So maybe this particular alternator was built for an engine that did not run as fast? Just throwing that idea out there, I believe it could be a factor.

[ERASER5]

No mater the pulley size or the rpm, the voltage regulator should regulate the output to something less than 15vdc. 13.6vdc is the standard target.

I would have a close look at the voltage sensing wire. My F**d had something similer wrong with it. If the sensing wire has a bad connection, it may be telling the regulator to increase the output. Mine told the reg to open ALL the way up. Very bad on the electrical system. Deadly to headlights.

[BobbyK]

Actually,14.2-14.5 volts is what your alt. should be putting out.
That's what mine puts out...well...14.1 actually.


15v is a little high though and ,as stated, the stock amp gauge is "normally" just to the right of the center line.Any more past that point and your in a Charge condition.

You could take it to a local Pep Boys or the like to get the alt. tested but the staff usually don't know how to hook up the machine to perform the test.
I recommend a local auto electric shop.

It may just be the gauge..it is after all...39 years old!

[truckdude239]

i replaced the alt on my f**d and it charges at 15 volts. now on my 71 i replaced the alt with one off a 83 chevy k-10 wiht 350 http://www.partsamerica.com/ProductD...ype=11&ptset=A
and follow ed the instructions in this tread
http://67-72chevytrucks.com/vboard/s...d.php?t=119379

and it charges about 14.6 volts head light are brigter no more dsead battery but only thing not stock is my cd play so i got prenty of power. but if i was you i get a new gage

[Longhorn Man]

everyone is saying the guage is messed up... yet both the stock guage and the multimeter in his hand are showing an overcharge condition.
If I installed an alt at work, and it was doing this, I'd get fired.

[67Fleet]

When I installed it, I hooked up the red power lead to the batt., and there were 2 other wires. I had to buy a new connector as the old one I had was a different configuration. The new connector has a red wire and a white wire. My wires to hook into it from the previous alt were black and brown. I hooked the black wire to the white wire on the connector and the brown wire to the red wire. Did I do something wrong?

[Longhorn Man]

you never bypassed the old voltage regulator did you?

[Longhorn Man]

like this;

[67Fleet]

HMMM...... I thought the PO would have done this. Maybe I thought wrong. I'll have to look tonight when I get home. Where is that LonghornMan? Pass fender?

[67chevy2wd]

Why take it in to get it tested, the alternator is already on the test bench(the engine) that is all a test bench is a motor to turn it and a carbon pile to put a load on it. Run the engine and turn all the accesories and see what it is putting out for volts, Don't use a multimeter to check amps unless it designed to you will fry the fuse, get and ammeter for that. It should say say what amps it should put out on the alternator. The gauge is fine like longhorn man keeps saying, the 15v tells you it is putting out too many amps, so the gauge in the pickup should be reading higher than normal. 13.5-14v is what you should see when you hook up a volt meter any higher is not normal and there is something wrong. So the problem is the regulator is not regulating the voltage like it should be for what ever reason. Longhorn man I don't understand how not bypassing the stock regulator would cause this, I know it has to be bypassed but could you still explain. If it were me I would check and see what I am getting for volts at my #1 and #2 terminals on the regulator if you did bypass the stock regulator. Help me out again longhorn man but isn't the energize terminal hooked up to the batt terminal on the alt and where does the sense hook up to again.

[Longhorn Man]

67fleet, the PO would not have done that, becouse he never converted it. The Alt with the square plug is the externally regulated style, which, since you had to replace the plug with the thin one, we know that you in fact had the square one.
I have never bothered to learn WHY running it through 2 regulators causes an overcharge condition, but I have seen it happen through the board here more than once.
The stock voltage regulator is on the drivers side of the rad core support, by the head light plug. I have it circled in my pic, along with a rats nest of wires the P.O. had there with his world famous dope smokin old man way of fixing things.

[67Fleet]

OK, cool! Thanks for the info! So now I'll just follow the info in the FAQ thread about converting and I should be good to go. Go-go taquito!

[see ten]

Both of my trucks only have one jumper wire where the old regulator was. Am I headed for disaster with this? Both trucks are running 108 amp Corvette alternators and everything seems to be working like it should. I had a buddy with a 68 Chevelle who had his jumped this way and I just copied his setup. As I said everything appears to be OK, one of the trucks has been this way for probably 8 or 9 years. Do I need to go back and add another jumper? Have I just been running on dumb luck all these years? Somebody throw me a bone!

[67chevy2wd]

I think it just depends on how you Alternator is wired too. How many wired go to you alternator?

[Longhorn Man]

there is like 3 or 4 ways of doing it... the way I showed is how I've done 3 trucks now with no problems. If your charging properly and not draining the battery, leave it alone.

[truckdude239]

Originally Posted by see ten

Both of my trucks only have one jumper wire where the old regulator was. Am I headed for disaster with this? Both trucks are running 108 amp Corvette alternators and everything seems to be working like it should. I had a buddy with a 68 Chevelle who had his jumped this way and I just copied his setup. As I said everything appears to be OK, one of the trucks has been this way for probably 8 or 9 years. Do I need to go back and add another jumper? Have I just been running on dumb luck all these years? Somebody throw me a bone!

if you look in the link above that i showed for the convert the only wires jumped is the ones on the outside

[67Fleet]

You guys have me confused now. There's multiple pictures on here and they're all different configurations. WTF????

[ERASER5]

Longhorn's method uses two jumpers at the old reg plug and the original two wires at the alt plug.

The FAQ method uses one jumper at the old reg plug and one old wire at the alt plug and on new wire.

Either way is good. I like Longhorn's method because the wiring still looks original at the alt.

[67Fleet]

YAY!!! Mission completed. Followed the FAQ and it's working flawlessly now. 14.50v at no load, 13.78v at full load with radio, lights, and air compressor running. Thanks for all the help guys, I truly appreciate it!!!
-Bret