Gen light stays on until I rev up the engine???

[Bartenfeld]

OK...the belt is tight and the wires are hooked up right. But when I first crank the engine my gen light is on and it stays on until I give the engine a good rev. and I mean a pretty good rev. (i dont have a tach so not sure of exact rpm, but pretty high) After the light on the dash goes off the headlights brighten up and I have never had battery problems, which indicates to me that the alt is charging prop. My question is, what could be the reason I have to "ramp" up my alt before the I can see a change in the electrical system. Could it be a voltage regulator problem?? or does this situation simply point to a bad alt???

[jocko]

What year is your truck? Reason I ask - does it have an altenator or a generator? If generator, what you're describing isn't exactly uncommon. Alternators will charge at all rpms down to idle. Generators, well, not so much. But, if I read you correctly in that whatever the issue is - it's gone shortly after initial startup (after the rev), then that concerns me a bit more. Anyway - pls let us know if you have an alt or gen and we can get the ball rollin here... If it's an alternator in your truck, then you definitely have a problem - should not do what you're describing, and may need replacement. If you have a generator, I (personally) wouldn't be as concerned. Drove a 57 around for years with a generator and occasionally had to do what you described - and not just immediately after start only.

[HEI451]

Usually, an alternator, either externally, or internally regulated, will have a "cut in capture rpm" of between 1,250 and 1,300 rpms, which is easily attained with a cold choke start engine, or the first rev of a warm engine after restart.

Generators are a whole different story, their cut in is done with one of the windings and energizing just past fire up.

[losthope]

a generator ,generates power when it is turned at a certain speed, so when you first start the engine the generator is not spinning at the right speed to produce enough power to turn the light out, when you rev it up it gets to the right speed and the light goes off, this is a normal function for a generator.......

a alternator isnt a generator at all, it charges the battery with power used from the vehicle.....so dont mistake which one you have..

if your battery is dead and you have a generator and you could get the vehicle moving fast enough (lets say down a hill or being pushed) the generator will produce power and charge the battery.......as with a alternator you could not...

[Bartenfeld]

1966 custom and it came with a 283ci engine. My grandfather replaced the engine in the 80's with a 305. Not sure if it originally had a gen or an alt but the light on the dash is labeled "GEN" if that tells you anything??? how would the electrical system act if the gen had been replaced with an alt??? Would it even work right at all??? Honestly, I still havent wrapped my brain around the whole voltage regulator componet...im used to to a one wire alt that goes straight to the battery.

[jocko]

For a 66, would have originally had an alt, and the replacement certainly would have an alt. Something seems not quite right if you gotta rev it to ge the light off...

Recommend:
1. check batt voltage with eng off
2. check batt voltage with eng running
3. check alt output and compare to #2

#1, want approx 12-ish V
#2 & #3 should be approx 14V with minimal drop in comparing alt output vs. at the batt.

Also - a quick alternator check is to stick a screwdriver to the rear casing of the alternator where the bearing is - and see if it's magnetic. That's a positive indication. If not, get a new alt. if it's magnetic, could still be bad, but at least you'd prove it's worth digging further.

[CSGAS]

That is the voltage regulator, but I wouldn't jump to the conclusion that it's a bad part yet.

First off, are you using a 1-wire alternator, or any other kind of setup that "cleans up" the wiring? Usually they don't trigger the alternator to start charging until the alternator RPM reaches 2000 or more RPM (what that equates to in engine RPM depends on the pulleys you run, I'm used to 1000-1250 engine RPM)

We'll see if that's the case before worrying about anything else; if that's it most people live with it just fine.

[Bartenfeld]

No its not a one wire alt. it's what I would call a normal stock alt. it has one hot wire running down to the horn relay and the two other wires that I assume trigger the light on the dash.

[Bartenfeld]

post #12 (the 1st diagram on the 12th post) shows my exact wiring, except I have an alt. Is this a problem?

http://67-72chevytrucks.com/vboard/s...d.php?t=378484

[jocko]

an "AC Generator" is an alternator. Post #12 shows an external voltage regulator also - but in your description in post #8, you did not mention any wiring to one(?)

You have an alternator - and you should have an alternator - a 66 wouldn't have ever had a generator - so, you're barking up the wrong tree wondering if you have a problem because someone converted your generator to an alternator - that hasn't happened. Your truck always had an alternator.

So, to resolve your truck's charging problem, need to do some troubleshooting, that's all, it's not the case that you have a problem because someone converted your truck to an alternator.

See post 6 for some basic first checks.
Confirm you actually HAVE a voltage regulator.

Just so we're all on the same sheet o music - the pics below are:
Alternator
Generator
Voltage Regulator

If your batt voltage is decent with the engine off, then you have likely narrowed the problem to the Alternator of the Voltage Regulator. Let us know what ya got.

[joedoh]

tighten your fan belt.

[jocko]

Good point!!

[Bartenfeld]

I have an alt and a voltage regulator. the belt is tight. could the voltage regulator be bad or going bad on me?? I'll get my volt meter from work tomorrow and let you know what kinda voltage im getting.

The main wire coming off of the alt (red) runs down to the horn relay then jumps to the voltage regulator. two wires (blue and white) run from the voltage regulator to the two prongs on the back of the alt. then one more wire comes from the voltage regulator (brown) and runs up to the "gen" light on the cluster. just like the diagram in post 12 under my link.

http://67-72chevytrucks.com/vboard/s...d.php?t=378484

[awbrown]

my truck does the same thing , but i also have a under drive pulley kit on it ...

[HEI451]

Yes, the regulator could be going out. That said, there are two types of regulators for those early alternator types.

One is a stock type, uses solenoids inside, is manual in operation, and, their settings can change inside. Most are adjustable, but, read below.

the other type regulator is an electronic regulator, not stock GM, but after market. I use the Wells VR715 electronic regulator for the early alternaqtors, converts their operation to the same as a so called single wire later internally regulated alternator, and no adjustment is needed.

I suggest the alternator you have now be taken to a testing facility, to test it off the vehicle, and if it is found to be good, then, find either the Wells regulator I listed above, or its equivalent from another maker.

Of course, an easier way to go would be to fit a later model internally regulated alternator to the engine, bolts right on. They can be obtained from local sources, use a 1980's 94 ampere Chevy Citation A/C alternator. If you do this, let us know, wiring it up so the GEN light is very easy, and it can be made into a "single wire" setup with only one jumper wire added to the outside of the alternator, BATT to terminal number 2 on the side. .

[Heater63]

And following up on all of this is reviewing some good information at this site:

www.madelectrical.com

read his Electrical Tech section, good info on 1 wire vs 3 wire, 10SI, 12SI, etc etc

[CSGAS]

Originally Posted by HEI451

Yes, the regulator could be going out. That said, there are two types of regulators for those early alternator types.

One is a stock type, uses solenoids inside, is manual in operation, and, their settings can change inside. Most are adjustable, but, read below.

the other type regulator is an electronic regulator, not stock GM, but after market. I use the Wells VR715 electronic regulator for the early alternaqtors, converts their operation to the same as a so called single wire later internally regulated alternator, and no adjustment is needed.

I suggest the alternator you have now be taken to a testing facility, to test it off the vehicle, and if it is found to be good, then, find either the Wells regulator I listed above, or its equivalent from another maker.

Of course, an easier way to go would be to fit a later model internally regulated alternator to the engine, bolts right on. They can be obtained from local sources, use a 1980's 94 ampere Chevy Citation A/C alternator. If you do this, let us know, wiring it up so the GEN light is very easy, and it can be made into a "single wire" setup with only one jumper wire added to the outside of the alternator, BATT to terminal number 2 on the side. .

X2...My external regulator closed up (it has points like an old distributor does) and instead of playing with it I got a solid state external (like the Wells part)

[Bartenfeld]

very nice link heater63!!!

[1963c-10]

Not uncommon to get bad "new" regualtors from the parts store either. Had 2 bad ones back to back from Autozone 2 months ago.

[Bartenfeld]

well folks, after reading and studying all I could about the alt and voltage regulator on my '66, I now realize that I am running an internally regulated alt. but the truck is still wired though the old school factory voltage regulator......so I actually have two regulators in the electrical system. I've figured out that I already have a 12SI alternator!! Im going to probe and test the alternator first, then go ahead and change the setup so that I can eliminate the mechanical external regulator. I really like the idea of headlight relays too. Not only are my headlight a little dim, but you can see the pulse of the old mechanical voltage regulator in the headlights and the dash lights.

If anyone has any issuse with their alternator or voltage regulator, just check out mad electrical!! THEY BREAK IT DOWN!!! like I said nice link heater63!



Here it is in case you missed it

http://www.madelectrical.com/electrical-tech.shtml

[JimQ]

Originally Posted by Bartenfeld

well folks, after reading and studying all I could about the alt and voltage regulator on my '66, I now realize that I am running an internally regulated alt. but the truck is still wired though the old school factory voltage regulator......so I actually have two regulators in the electrical system. I've figured out that I already have a 12SI alternator!! Im going to probe and test the alternator first, then go ahead and change the setup so that I can eliminate the mechanical external regulator. I really like the idea of headlight relays too. Not only are my headlight a little dim, but you can see the pulse of the old mechanical voltage regulator in the headlights and the dash lights.

If anyone has any issuse with their alternator or voltage regulator, just check out mad electrical!! THEY BREAK IT DOWN!!! like I said nice link heater63!



Here it is in case you missed it

http://www.madelectrical.com/electrical-tech.shtml

Holy cow. I'm glad you figured that out. I have a '64 that was converted long before I got it. I had the same symptoms as you do. I replaced the alternator, FIXED. It's been a while but I believe it was a bad diode in the alternator. These alternators are CHEAP. Hang a new one and see what happens.

Good luck man.

Q

[Bartenfeld]

I havent tested it yet, but the one on my truck now charges fine. (planning on keeping it on there) I just knew something wasn't right somewhere and wanted to fix it.