Not sure whats going on with my alternator

[SeanT4x4]

So I have a basically brand new 100 amp 1 wire alternator. The one charge wire runs directly to the positive post on the battery. I also have an aftermarket volt meter in the cab.

Everything seems fine during the day and the meter is reading right around 14v. At night when I run the headlights the volt meter drops to just above 12v.

I have the after market H4 head lights with the wire harness pulling straight from the battery. I verified the voltage on the post of the alternator at 12.3 with headlights on. I would think this alternator should be more than capable of keeping up with basically just the headlights and marker lights.

Any idea why its dropping to battery voltage with the headlights?

 

[69red]

check the grounding of the alt.

with the truck running, turn on the lights and check the voltage between the case of the alt and the negative battery post (not the clamp) using your multi meter. it should be less than 0.1V.

then do the same thing from the output lug on the back of the alt and the positive battery post. this also should be less than 0.1V

if either are greater, then clean the connections at each end of the wires and try again.

if that doesn't fix it, then take it in and get it tested.

 

[Rustytruck]

Make sure the belt is tight and the nut on the pulley is tight. Do you have a unusually large diameter pulley on the alternator? What is your idle speed? If you kick it up to 800 rpm at idle does the issue still remain?

 

[SeanT4x4]

So i just checked the voltages with the truck running and both are under 0.1v

Right now there is no ground wire on it because i believe it is supposed to ground through its mounting point.

Nut and pulley are tight. I don't know about the size of the pulley. Its whatever was on it out of the box.

I replaced the alternator and the belt at the same time and both are new. The belt feels pretty tight and I have never heard and screeching or squealing to make me think its slipping. I don't know about my idle speed since I don't have a tach. The problem persists at cruising speed though.

While checking I did notice the pulley had become discolored since installation, not sure if that means anything. I was the same finish as the pulley just a week ago.

I'll put a ground wire from the case to the frame and see if that changes anything.

 

[treihesse]

Make sure you have a ground that goes battery engine block frame and body you could be getting a bad ground

 

[Viperwolf1]

So i just checked the voltages with the truck running and both are under 0.1v

Right now there is no ground wire on it because i believe it is supposed to ground through its mounting point.

Nut and pulley are tight. I don't know about the size of the pulley. Its whatever was on it out of the box.

I replaced the alternator and the belt at the same time and both are new. The belt feels pretty tight and I have never heard and screeching or squealing to make me think its slipping. I don't know about my idle speed since I don't have a tach. The problem persists at cruising speed though.

While checking I did notice the pulley had become discolored since installation, not sure if that means anything. I was the same finish as the pulley just a week ago.

I'll put a ground wire from the case to the frame and see if that changes anything.

That belt is slipping under load. You very little wrap around the pulley and the belt looks too wide for it.

 

[SeanT4x4]

Is there a standard Vbelt pulley width? I did notice that it doesnt sit flush on the pulley like it does on the others.

I was looking on summit for a pulley that might fit better but none of them list the belt groove width.

Im also not sure on the bore diameter...

 

[blubuckaroo]

Could you post a photo that shows more of the belt path? Like Viper noticed, there is very little contact between the belt and pulley. The belt angle at the top doesn't look factory.

 

[SeanT4x4]

It definitely isn't stock. There is an A/C compressor the is probably messing with the angle. The bracketry for it almost looks home made, it was on it when bought.

 

[Justafordguy]

X3, not enough belt contact and belt doesn't fit pulley very well. It's slipping. that's also also why it's discolored, the slipping is making it get real hot.

 

[malonejy]

There are different width belts. I found that out troubleshooting a problem similar to yours

 

[SeanT4x4]

I know there are different width belts and this is a10mm. It fits all the other pulleys well, just not this new alternator pulley.

Everything worked well for a week and I got rid of the old pulley... Like a fool

Looking on summit I couldn't find any specifications on belt width for the pulleys they sell.

Ended up ordering a double V (no idea on belt size) hoping I can find a belt that will be the right length to go around the extra groove on the compressor and the alternator to give it the grab it needs.

Might only be lawn mower belts that short though haha

 

[moses_m]

alternator

Hi Sean sweet bronco

Sean if you ever want to do the explorer setup I have a brother in law that lives is Algodones that has done it twice. Including the one on mine and he also had the AC hooked up. Just trying to help out a fellow member and of course some business for my brother in law. Dont be afraid to go to Algodones as hundreds of snowbirds cross daily and most of my brother in laws customers are snowbirds during the winter time. They are just trying to save a litte money like anybody else.

Was hoping to see your bronco on the streets while I was down there over the holidays. Saw a green one and a orange one in curevos on new years day. Saw a clean silver one like yours on a lot by the freeway last year. Did you buy yours off the lot by the discount tire by the freeway?

On your current problem. Do you use the AC if not I would run a different belt with a bigger pulley. Would of also ran with the 3G alternator 140 amp.

 

[Hozr]

V'belts are not meant to run on the "flat" part of the pulley. They are meant to pinch in the v without bottoming out. If the belt is sitting on the flat part it will slip.

 

[SeanT4x4]

Hi Sean sweet bronco

Sean if you ever want to do the explorer setup I have a brother in law that lives is Algodones that has done it twice. Including the one on mine and he also had the AC hooked up. Just trying to help out a fellow member and of course some business for my brother in law. Dont be afraid to go to Algodones as hundreds of snowbirds cross daily and most of my brother in laws customers are snowbirds during the winter time. They are just trying to save a litte money like anybody else.

Was hoping to see your bronco on the streets while I was down there over the holidays. Saw a green one and a orange one in curevos on new years day. Saw a clean silver one like yours on a lot by the freeway last year. Did you buy yours off the lot by the discount tire by the freeway?

On your current problem. Do you use the AC if not I would run a different belt with a bigger pulley. Would of also ran with the 3G alternator 140 amp.

I'm definitely not afraid to go to Algodones although I have been a little sketched out about getting vehicle work done down there. The idea of leaving my bronco in another country is a little weird. I'm fairly capable of working on things so maybe its time to look more into the explorer setup. Never really gave it much thought.

I dont think Ive ever seen a green one in Yuma. There is another member on here in Yuma, I think his is black though. I saw that silver one at the lot by Discount too. Its much cleaner than mine. Mine looks good from 30ft haha. Its more of a baby blue silverish.

I really dont use the AC. It was on there when I bought it and was told there is a leak. Havent got around to messing with it. Maybe I should just bypass it until I decide to get it working. I'll see if I can rig something up with the double pulley I have coming and the double groove on the compressor.

 

[SeanT4x4]

Anybody have a picture of how a compressor should be mounted on V belt setup?

 

[blubuckaroo]

Anybody have a picture of how a compressor should be mounted on V belt setup?

Your compressor appears to be mounted properly. The alternator should be driven by a belt that goes over the water pump and crank pulley. The compressor should be driven off the crank pulley by itself and needs a tensioner pulley mounted above the water pump.