• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

6.2 Grumman charging question

Did you check the pully size on the alternator? To big a pully will result in less output.

Where did the alternator come from? If it was a rebuilt from Aitozone I'd be inclined to take it back, trade up & pay the difference for a new, not rebuilt if they have one available.

Did you have the alternator checked since it is showing low voltage while running? I'd take it back to where it came from or preferably to a good rebuilder and have it tested. If it's putting out 12 volts now it will probably be weak under a load.
 
had it tested, tested good. just got word the truck is down and wont even jump. any ideas now? try a 5th alt?
 
How would I do that? for what its worth the stud was 12.2 with it running and the batts were also 12.2
 
ak diesel driver said:
It would basically be a continuity check possible high resistance.
Click to expand...

I have to drive out to the truck witch is about 2 hours away in the middle of no wear, would you happen to know what gauge wire that is so i cant take some with me? :eek:
thank you again for all your help
 
Does this have a guage or an idiot light? If it had a light, if the bulb was bad then it wouldn't charge. Also I can't remember which wire but one of the wires needs to have 12v to the alt to excite it. Been awhile since I messed with this so I'm a little rusty.
 
gauge and it reads about 12. same with the lights on, 4 ways flashing, and heater blowing. it never drops below 12.2, but i guess it did now that its dead
 
If it won't even jump could be other probs maybe interrelated sometimes things have to totally fail to find the problem. sorry I'm not more help
 
you have been a ton of help! thank you so much for your time, ill let you know what i figure out. this truck is driving me nuts
 
They said the alternator tested good.
Can you disconnect the wire from the stud and recheck the stud with the vehicle running?
If the batteries are reading over 12 volts the truck should start, especially if it's warm.
If the batteries are at 12 volts, the battery is getting some charge. I would try to jump the starter. The safest way is to install a push button from the small starter stud to the positive on the battery. The easy but dangerous way is to croos the studs at the starter with a screwdriver. Make double damn sure the truck is in neutral.
The batteries have been load tested - correct?
I had 2 new batteries that would not load test. If you have dual posts always do all your testing off the posts that you are using. You can have a good battery with bad posts.
Upgrading the charging wire or adding another wire going to the other battery is never a bad idea. But I don't think this is your issue.
You could also check voltage at the starter

What exactly is the truck doing when you hit the key to start? If the answer is nothing and you have 12 volts something other than the alternator is wrong.
 
batts have been tested good, and it use to start and run at 12.2, now the starter wont even click on. the glow plug relay does click but doesn't sound right. i think the batts are almost completely dead now


there seems to be a relay on the firewall on the drivers side that looks like the alt hot wires goes to, but there isnt one any any of the other trucks. could that be something to do with it?
 
That looks like the fuel pump relay that's on my 94. The red wire on the stud on the back of the alt should go directly to the batt, sounds like it's missing and that would be a no charge situation. It's a fusible link wire too but you could use a inline fuse as well.
 
When you had the alternator tested, did you ask if it had an internal voltage regulator?

Make sure the alternator has a built in voltage regulator before you run a wire direct from the alternator to the batteries.
 
You must log in or register to reply here.
Back
Top