Awhile ago I had a huge electrical short. Took out my fusible links, light relay, and every light in my truck blew except headlights. After getting everything fixed and working correctly, I find out that I have an overcharging problem .So the alternator has tested good time and time again(new unit). I have continuity through my wires. Im currently on my 4th new regulator. When I turn the truck on, I watch my voltage is slowly rises, eventually overcharging. Now if I put any load on the system at all it holds strong right at battery voltage. Now if I rev the truck up a little, it will go back to overcharging even with having accesories on. The battery light on the dash does work and is currently staying on. I just find it hard to believe that Im getting dud regulators. Id really appreciate some tips. Maybe some things Im not checking in the wiring?

 

Did the wiring get cooked at the alternator? Did wiring get cooked at the regulator? Was any wiring repaired? Does the regulator have four wires [IC electronic] or five wires[point type]?

 

No wiring did not get cooked at the alt. Mine is the 5 wire setup. Does not looked cooked, clean ends, no breaks in the wire. Having a proper diagram wouldn't hurt.

 

I will sling you a '79 wiring diagram, as well as charging system info, when I get home after work =).

 

Home yet?

 

Yep, just a sec and it will come your way!

 

crap. the scanner is broke =/

Here are some resources though:

Download your FSM, there is a good wiring diagram in the back
http://ncttora.com/fsm/index.html

Basic alternator info:
http://www.autoshop101.com/trainmodu...or/alt101.html

More basic alternator info:
http://www.madelectrical.com/electrical-tech.shtml

Charging System info for 22r motor (even though you have a 20r, a lot is the same):
http://www.ncttora.com/fsm/1990-1995...i/charging.pdf


Alternator Info for Toyota Vehicles, includes voltage regulator pinouts:
http://www.home.earthlink.net/~twopapa/bigalt.htm


I wish I had more info for you. Eventually, I will be posting detailed info in a total re-wire thread I am creating, but I don't have it all together yet....

 

So the IG wire at the regulator shows ground with key off. Then shows voltage when key is on like its supposed to. That wire supposed to be a ground with ignition off?

This truck is throwing me in circles. Can't find a correct wiring diagram anywhere.

 

i had the same prob and i took it to an auto electrical shop and they said there are two diffrent types of alternators with the same plugs one that runs off the neg and one that runs off the pos and all auto parts dealers have the wrong ones he gave me the right one i swaped it in the parking lot there and the light went off and havent had a prob since

 

A picture of said alternator would really kick ass

 

ok well i can get them tomorrow

 

Thanks, would appreciate that.

 

Hey not to jack at all, but what ended up being the solution to when all bulbs and fusible links went out? (Im trying to fix an identical problem I lost everything but signals and headlights I am having the overchargin problem also

 

There are two fusible links. One for the alternator, the other for the accerories. The links got hot melted and took out some other stuff. Fusible link is just wire that is designed to burn like a fuse. You can buy it at your local autoparts store

 

ok so i couldnt take a pic of the two alternators but the look the same but on the back there is a green plug with three prongs they both have the same one and the only way to tell the diffrance is the letters next the the prongs here is what they look like

the one u want The bad one

_ L _ F

l l l l
E F E N

That is how the letters should read next to the green plug

 

lol that didnt turn out right

the good one lookes like

_L

E l l F


The bad one looks like

_F

E l l N

 

Have you thought about getting rid of the toy alt. and replacing that and the regulator with a one wire GM alternator? You would have to fabricate a bracket for the alternator. I did this on my 81 and used a 110 amp alternator. It works great.

 

Thank you, your the 3rd guy to tell me this, but the first to explain which alternator I needed

 

79TONKATruck is correct. I probably should have remembered that , but we drank alot back in the 80s. All hail 79TONKATruck.

 

The fusible links on mine are fine, I figured out im getting power to and out of the fuse box too.