What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Truck won't shut off

mtnman210

mtnman210

1/2 ton status
Joined
May 30, 2003
Posts
3,880
Reaction score
0
Location
Northridge, Ca
I'm trying to finish up the wiring on the project and I'm back to the alternator problem again:doah: The first time I couldn't get it to charge. Ended up looking through a couple diagrams and came up with this

Bat terminal on back of ALT: direct to + on battery
#1: ignition switch
#2: either jumped to bat post on ALT or run all the way to + post on Battery

Now this isn't a normal column and dash setup up it's in the trail rig. I'm running a simple switch panel and have a designated IGN switch. So I've run the #1 wire to the switch and the rest of the wires as stated. I've tried #2 both ways and still have issues.

So with the wires run according to the above. I finally get a charge with the truck running but I shut off the IGN switch and even the main battery cut off switch and the truck will stay running. Any ideas???
 
can you get a pic?im assumunig it started and ran before, but not charging. it sounds like the alt has become a ground for the battery.and maybe the ignition switch is being bypassed because of that? the whole body ground thing. mine changes what works and what doesn't everytime i wheel it. sometimes the battery ground is on the frame, sometimes on the fender.so I know the frustration.:rolleyes:
 
You need to put a resistor in the #1 wire between the alternator and the ignition switch. A small light bulb works perfectly and is cheap and easy to find.

What happens is the alternator is applying voltage to the ignition switch even when the switch is turned off. Splicing a light bulb (or large diode or resistor) adds enough resistance to the circuit to prevent the alternator from back feeding the ignition ignition circuit.
 
You need to put a resistor in the #1 wire between the alternator and the ignition switch. A small light bulb works perfectly and is cheap and easy to find.

What happens is the alternator is applying voltage to the ignition switch even when the switch is turned off. Splicing a light bulb (or large diode or resistor) adds enough resistance to the circuit to prevent the alternator from back feeding the ignition ignition circuit.
Click to expand...


Or throw a single wire alternator on it and be done......
 
well I fixed the won't shut off problem....now it won't start, not even a click:doah: I've been tracing connections all morning and finally found a bad ground. I replaced it and got it to fire backup. Haven't tried the alternator yet.


and forgive my NOOBNESS, but resistor?? kinda new to the whole wiring thing. is that something I can just pick up at radio shack or a parts store?
 
mtnman210 said:
well I fixed the won't shut off problem....now it won't start, not even a click:doah: I've been tracing connections all morning and finally found a bad ground. I replaced it and got it to fire backup. Haven't tried the alternator yet.


and forgive my NOOBNESS, but resistor?? kinda new to the whole wiring thing. is that something I can just pick up at radio shack or a parts store?
Click to expand...


Yeah Radio shack has a nice selection of resistors in there bins of random stuff.. Not sure what size resistor you need though.
 
Here is a nice diagram that shows the proper wiring.

AlternatorWiringOverview-1973to1985Buick.jpg


The factory uses a resistance wire where the resister is shown above. If you dont have the resistance wire you can us a 10 ohm/1 watt resistor to get the job done. Rat shack link to resistor.

http://www.radioshack.com/product/index.jsp?productId=2062294


Hope that helps.

Cheers,

Rufus
 
I've seen that diagram too. I've just left out the light/resistor. I guess I know what I need to try next.


and for reference I think I've found some info on what type of resistor.

The GM 10 and 12 SI series alternators need 10 Ohm 10 Watts of resistance in the circuit (the 12V switched exciter circuit, not sure what the technical name for it is). Without this, they go to a full charge state (like 37 Volts or something). Cars with out an idiot light will have a resistor or length of resistor wire, and in cars with an idiot light, the light bulb istself is the resistor.
Click to expand...
 
Problem solved!!! Put in the resistor on the wire from the #1 post to the ignition switch and all is good now.
 
had this issue when I put an MSD 6a in my rig with a remote coil. just had a little trickle of power going to the box to keep it running. resister inline killed the trickle.
 
Actually,the resistor in that diagram,as stated before,limits the amount of current getting to the feild coil in the altenator,so it wont put out "maxumum" charge..apply a full 12 volts to the feild,and it'll put out the maximum amperage the altenator will produce..less voltage "in" = less amps out..so you need either a light bulb,resistor or resistance wire in that #1 wire from the ignition to the altenator plug..

If you put a DIODE in the #1 wire from the ignition to the altenator plug,that will only let the current flow TO the altenator,and not "backfeed" the ignition curciut--dides can be had at radio shack,they'll have an arrow on them indicating the direction they'll let the current flow,point it towards the altenator,and you wont have the "it wont shut off" problem anymore..
 
inside the alternator on the rectifier is already a diode thats supposed to not let the power backfeed.i had a rebuilt alternator that i got from autozone with a bad diode and had to replace it again.problem solved.
 
Far as I know there is a "Diode Trio" in the altenator that works with the rectifier to change the AC voltage to DC,but I dont know if its also there to prevent backfeed to the #1 wire on the plug--I read this "fix" in an old Hot Rod magazine many moons ago,it was a common problem in cars with the "old" externally regulated altenators guys wanted to swap the later 10SI Delcos into,they couldn't get the engine to stop once they started it!..this was the easiest way to cure it they claimed..
 
diesel4me said:
Far as I know there is a "Diode Trio" in the altenator that works with the rectifier to change the AC voltage to DC,but I dont know if its also there to prevent backfeed to the #1 wire on the plug--I read this "fix" in an old Hot Rod magazine many moons ago,it was a common problem in cars with the "old" externally regulated altenators guys wanted to swap the later 10SI Delcos into,they couldn't get the engine to stop once they started it!..this was the easiest way to cure it they claimed..
Click to expand...
yep the diode is supposed to let the input voltage from pin 1 to excite the main windings go in and not backfeed as soon as the ignition is turned off.it gets its primary voltage from the ignition switch first to know when to turn on.if that is replaced with a constant power supply,it will keep telling the alternator to put out power and that will keep feeding the ignition power and be running off the alternator alone.you can check for this by putting a multimeter on the batt terminal on the alt and it should only give infinity when negative is on the batt and positive is on pin 1.hope that makes sence.i just went the easy rought and got a one wire alternator so i didnt have to worry about 3 extra wires and resisters and such.plus then i could bypass my external voltage regulator and take out one extra variable in my charging system.
 
You must log in or register to reply here.

Latest Posts

Top Bottom