Hey Rob or anyone who KNOWS and not speculates,

As you know I'm popping alternators left and right on this damn truck. Someone brought it to my attention that you need a resistor in between the generator feed off the alternator and +12v. Said it happens on the newer high output alternators.

Can you verify this for me? I don't have the service manual to this motor anymore and doubt I will be able to return alternators too much longer. #4 should be here tomorrow..

Preciate any help.

Fried Jeff

 

The small wire needs 12v on it when the key is on to turn on the voltage regulator. If there is no voltage to it, there may be no alt output.

 

thanks rob, preciate the reply.

ANYONE trying to retro fit a new style engine into an earlier vehicle needs to pay attention to this. I would have never of paid attention to this if someone hadn't brought it to my attention.



looks like i need a 470 ohm resistor in there, but reckon i'm on my own as to what wattage.

 

I have seen the resistor that was specified in the diagram, but was unsure if that was just for the tell-tale lamp or what.

 

I'm pretty sure it's in there as a current limiting resistor for the voltage regulator. If you look at the diagram, the reg is slamming +12 straight to ground to get the exciter fired up. If you don't limit the current, it fries the voltage regulator. Trust me, I know.

Can't wait to get home from work today and get this puppy on the road. It's been too long!!!!

 

Hotwire,

Please let me know if this works....and what resistor you ended up using....as I am wiring up a race car in the next day or so and will have the same issue.



Thanks,

Randy

 

Working out the wattage, you need a 470 ohm 1 watt resistor. I didn't have time to really look for any, so I got two 1K ohm 1/2 watt resistors and put them in parallel.

By putting them in parallel, it halved the resistance to 500 ohms and added the wattage, so I basically made a 500 ohm 1 watt resistor.

I cut the generator feed right behind the alternator, soldered in the resistors and put heat shrink on them, they are basically lined up w/ the front of the valve cover and are protected under the alternator.

took it for two trips down the road, headlights, dual flexalite fans and all, no problems.

I am so freakin happy this project is coming to a close!!

 

 

SWEET.....

Glad it worked....now I can make the change to mine this weekend...although I will probably put the resistors in the car to avoid damage...wire is running to a kill switch in the car anyway!



Randy

 

LOL, should have let you sweat it a little bit.

I really sucks sitting there with V8 S-10 rumbling, checking everything out, going WHOO HOO it's working... aww ****. New alternator, WHOO HOO it's working... aww ****. etc etc.

I hope you aren't hooking the generator feed on the alternator up to a switch, no feed back from voltage will pop the regulator as well. Trust me. I know.

 

By "generator feed" do you mean the charging output wire? NOT the one with the resistors?

I mean...there are really only two wire eh?



I have the little wire (with the resistors) wired to a kill switch, that will kill ALL power and the alternator by eliminating the feed, so that the car will NOT run off of the alternator alone when "killed"...it goes to an ignition hot source. The charging output wire will go from the alternator to the starter and join with the battery lead.

Will THAT work?

Thanks,

Randy

 

as long as you are not running the car without the generator feed wire in loop, you will be alright. If you are running the engine without the feedback to the voltage regulator it will kill it.

By generator feed / voltage regualtor feedback I am talking about the 14-16 ga red w/ white stripe wire in the harness that plugs into the bottom of the alternator. it's a big plastic harness with about 4 or 5 pins, but just has the one wire coming out of it. It's supposed to go into the factory instrument cluster, go through the 470 ohm resistor, then tie to battery source. Check out the schematic I posted above.

I was running the alternator without the generator feed wire hooked up and said buh bye to alt # 1 & 2. #3 was taken to the grave by full +12V unlimited current input through the generator feed wire, #4 is hanging in there w/ the resistors in circuit.

Good luck.

 

Hotwire,

That is what I thought.....just wanted to make sure....I have an old alternator, and don't have the luxury of exchanging them at the local Kragens!

Thanks again,

Randy