Need help with alternator
 

I have a 72 k20 and I need to upgrade my alternator so I can run dual electric fans. The current alternator has 1 wire which from what I read means itÂ’s internally regulated. I also have on the front of my truck on the core support an external voltage regulator. When I first got my truck I had problems with dead batteries and once I replaced the external voltage regulator I havenÂ’t had a problem since. So it makes me think itÂ’s hooked up? The single wire from the alternator runs to the fire wall into a plastic harness I assume it goes to the relay inside the cab? IÂ’m confused on what alternator I need to purchase. Do I just get a single wire one and use a thicker wire and run it from the alternator to the relay? Do I need to remove the external regulator or by pass it as IÂ’ve seen in a few forums

Re: Need help with alternator
 

First, we need to determine exactly which alternator you currently have.. If, indeed, that voltage regulator is in the system, you'll have more than one wire on the alternator. Post a picture that shows the areas of the alternator where all the wires connect..

[B]"The single wire from the alternator runs to the fire wall into a plastic harness I assume it goes to the relay inside the cab?"[B]That wire is part of the main power distribution circuit. It has several "branches" that go everywhere. While we're on the subject: Go to the ELECTRICAL forum and download a copy of the electrical wiring diagram for your truck. It's the number one needed tool for electrical work.

You'll need an alternator output that will keep up with all the electrical demands. Typical radiator fans draw ~ 20 amps each. Air conditioning (if you have it) needs +/- 30 amps.. Lights, wipers, radio, and other electrical items will need another 15 amps approximately.. That's approximately 85 amps. A 100 amp alternator will provide enough "cushion" to keep the battery charged. If you insist on keeping that external voltage regulator, you'll more than likely need to have an alternator specially built.

Re: Need help with alternator
 

I recomend you not do electric fans. I did 2 years ago. Very hard on the electrical system as designed nearly 60 years ago. Electric gives you little if any real lift over a correctly configured mechanical setup. If you must go electric, Powermaster makes very good alternators and will have the correct type. Internal, external and one wire, all in multi levels of power. Our electrical system was designed 55 years ago. The wire from main splice to fuse link close to the battery is too small for fans. If you connect at the main splice or horn relay, the fans pull too much from the jump to fuse link junction and you could over heat the main line or kill fans from low amps if alternator is not turning. If you connect at the fuse link junction, the battery Meter is confused by the hi amps being pulled at the wrong location in the harness and again the wire from main splice to fuse link junction is undersized and likely over heat if you run air lights and fan at same time..

Re: Need help with alternator
 

I agree on not using electrics. Electrics actually made my truck overheat. I went back to a clutch fan and shroud

Re: Need help with alternator
 

I’m unable to use a mechanical fan. My engine sits too low and the fan shroud won’t line up with the engine. I tried replacing all the rubber mounts and engine mounts shimming etc…. I can’t get the engine raised enough.

Re: Need help with alternator
 

https://ibb.co/184sVfghttps://ibb.co/184sVfgI suck at getting pictures to attach. Hopefully this link

Re: Need help with alternator
 

The link didn't work for me. I'm interested in what engine your truck has in it.

Here's some links that may help you.

First on 10si and 12si alternators the most common swaps on our trucks. It may help you identify yours.

http://www.madelectrical.com/electri...elcoremy.shtml

Second on how the externally regulated alternator and internally regulated alternators work.

http://www.madelectrical.com/electri...evymain1.shtml

http://www.madelectrical.com/electri...hreewire.shtml

How I converted my Burban. Starting at post 467.

http://67-72chevytrucks.com/vboard/s...or#post8564188

And lastly a thread on how to post photos from your computer that may help you.

http://67-72chevytrucks.com/vboard/s...d.php?t=627506

Good luck keep us posted on you progress.

Re: Need help with alternator
 

I’ll have to upload images at work on Monday. I can’t get it to work off my phone

Re: Need help with alternator
 

vardenafil, your link actually worked, but you edited your post and took the link down.
You have a 10si alternator which would have an internal regulator. You also have a voltage regulator which was used in the original 10 DN alternator.

You have a frick'n electrical mess.

Your truck is typical and the reason these trucks should not be converted to internally regulated alternators.
80% of the people doing anything electrical on '60s vehicles, don't have a clue in hell what they are doing.

Re: Need help with alternator
 

your pictures.

Re: Need help with alternator
 

Six years ago I fought my electrical gremlins.... upgraded my alternator & wiring, and added 2 pusher fans. Here's a link to my thread https://67-72chevytrucks.com/vboard/...d.php?t=772236 in case you find it to be helpful. It's a lot of reading but contains a ton of good info from several great board members. Oh by the way, everything is still working perfectly since I did the upgrade.

Re: Need help with alternator
 

I would direct the OP to Mad Electrical . The site will bring you up to speed on the original wiring in your pickup. It also has a dedicated page on how to upgrade to an internal regulated alternator. They also have great components to greatly improve the efficiency of your electrical system…:metal:

Re: Need help with alternator
 

If that is a 10SI and charging the battery OK with only the one wire connected, then it may be one that has been converted to 1-wire. It's possible the external regulator is not doing anything. If it were mine I would disconnect the external regulator and test if the alternator still charges the battery. Because I would be too curious.

Re: Need help with alternator
 

It would still charge, it's just not getting a trigger through the brown wire. Probably when he hits over about 1200 rpm it kicks in. So yeah, he could unplug the external and it won't make a difference. He's just back feeding the battery through the system...If you pull the tape off the harness you can see where the red wires go. I posted up--just recently--how I've been wiring these for years. Don't remember which forum though.

Re: Need help with alternator
 

WHen i first got the truck i would charge the battery overnight and the truck would start two or three times, and the battery would go dead. it didnt matter how far i drove the truck it would never charge. i took the truck to autozone they told me the alternator was good but the regulator had gone bad. i replaced the regulator and now the stuck starts every time. so i assume the external regulator is doing something? I will try to unplug it tonight and drive around a bit to see if it does anything. i cant drive too far though as my radiator currentlyu has no cooling fan hooked up.

i have noticed that at idle the voltage drops really low to like 10v. when i start moving it jumps to 14v. would the easiest fix be getting an external alternator unit and keeping the wiring that is there or getting and internal regulated unit and doing the wire work as seen in this form to bypass the external unit? im thinking i need at least 100amps.

Re: Need help with alternator
 

thanks for those wiring diagrams. im going too look at them to see if my wiring was messed with. hopefully everything goes where it should

Re: Need help with alternator
 

Your alternator is "clocked" wrong, making it almost impossible to see the 2 small wires in the plug. One wire is for the charge light/resistor circuit, and the other is the voltage sense wire. With an external regulator, these wires go to the regulator. With an internal regulator, the charge light wire goes to the ignition switch, while the voltage sense wire goes to a point on the main power feed wire near the firewall connector.

This plug is very different for internal and external regulators. Is it possible to get a picture of that plug.

Re: Need help with alternator
 

As far as your fan hitting the shroud and your engine being "too low". Do you have the correct radiator sitting all the way down in the correct saddles?

Gary

Re: Need help with alternator
 

This needs to be said.. Very seldom will even the best of fans, electrical units won't cool as good as a functioning fan clutch and shroud.. One of those seven blade "paddle wheel" fans will really move some air through a radiator with a proper shroud. If your fan doesn't fit the shroud, more than likely you have either an ill fitting radiator or the wrong shroud.

Re: Need help with alternator
 

i have confirmed that i have the right shroud. i ordered a second shroud from lmc trucks? it was made specifically for 4x4 trucks. the shroud was too deep and i couldnt get the shroud over the water pump. the fan blades would of sat too deep into the shroud. the shroud so i sent that back. the shroud i have now is a sbc fan shroud non 4x4.

i have replaced the radiator mounts and the engine mounts trying to get the clearance i need. the fan blades have an 1/8 of an inch clearance on the bottom and will occasionally scrape. the top of the shroud the blades have almost 2 inches of clearance.

ive had 2 radiators in this truck. the what looks like original radiator and a brand new 2 core aluminum radiator. both radiators have fitment issues with the fan. the truck will over heat at slow speeds and idle with the fan set up as is. i assume the fan isnt pulling enough air because its not alligned prperly.

Re: Need help with alternator
 

https://www.imghost.net/tt08Q5PGhuNH4fb

these wires? maybe they fell out?

Re: Need help with alternator
 

>> When I first got my truck I had problems with dead batteries and once I replaced the external voltage regulator I havenÂ’t had a problem since. <<

It's possible that the original external regulator had a internal short. Replacing it took the short out of the circuit.
The original should have been mounted on rubber "Well Nuts" to isolate it from vibration damage. Yours is not.
I see that you do have the ground wire, which is nessecary when the VR is mounted on the three rubber feet.

Your alternator is stamped 37 Amps. A 37 Amp alternator will drop down to about 10 Amps at idle, but don't confuse that with the 10 Volts you said you were getting.
Because your Internally regulated alternator is wired incorrectly, it has no output at idle, so you're just reading battery voltage. 10 volts does seem awfully low if the only drain on the battery is the ignition system.
A 10 Amp idle output should get the battery up to about 12.5V at idle, but by todays standards, most want more at idle.

If you look at the advertisements for 10DN externally reg alternators, most advertise about 55 Amps.

I might doubt you really need a 100 Amp alternator. It would depend on how big the fans you want to use, plus anything else that draws a lot of power.

Re: Need help with alternator
 

I doubt that they "fell out". That alternator is an internally regulated alternator. The 3 screws mounting the regulator to the inside of the case are clearly visible. The picture of those loose wires doesn't show the details very well but it appears the plug is for a 10SI or 12SI, alternator, both of which are internally regulated. This plug will not connect to a 10DN alternator due to it being physically different. I suspect your alternator is internally wired as a "one wire" alternator.. We need to see a better picture of the back of it that shows the area where that 2 wire plug normally connects.

The picture of the voltage regulator definitely shows it's plugged into the wiring harness. Where the other end of those wires go is anybody's guess. If you have one does the "alternator" light function?? If your truck has an amp gauge, I doubt that it works properly. How all that wiring mess and external voltage regulator works with your present alternator beats the hell out of me. Your alternator is marked as a 36 amp and that will definitely not keep the battery charged with the loads you want to put on it. Vardenfil, with all due respect, you've got a wiring nightmare there.

Re: Need help with alternator
 

I'll make this one last statement and then I'll bow out of your discussion.. NO, you do NOT have the correct shroud. K/20s take a different shroud from the 2WD trucks. The reason being, the engine sits in a slightly different location. You probably have other issues there also. Wrong motor mounts, wrong mount brackets. twisted, bent, or misaligned core support, wrong transmission cross member.. Also trucks of these years had a short water pump and short fan clutch "snout".. Wrong parts here can certainly cause shroud fitment issues. There could be several issues at work here..

I'm not disputing any of the suggestions or opinions posted by others on this thread when I say the following: I suggest you entrust your truck to someone who really knows these old truck. Let him diagnose your problem(s) first hand.

Re: Need help with alternator
 

Looks like the original 10DN connector plug to me.