i have a 1985 ford f-150 with a 300 6. it quit charging so i replaced the voltage regulator. it didn't help. so i replaced the alternator, still not charging. i checked the wiring everything is correct and i have good grounds.

this is where i get very confused. i was checking wires with a test light and with the light hooked up to the postive terminal of the battery when i touched the s terminal of the voltage regulator it started charging at 13.5 volts (checked with a multimeter). it contined to charge even with the test light removed. when i shut the truck off and restarted it, it was not charging again until i used the test light.

i am very confused about this and any help would be greatly appreciated.

 

You are not getting a signal from the ignition switch. The "s" terminal on the regulator gets a 12v signal from the ignition switch circuit to activate the system to charge. You simulated this by using the testlight on it.

 

ok so how do i fix this

 

You will have to follow the red/green wire that is hooked on the "s" terminal back, and find where it's broken or disconnected.

 

the wire on the s terminal goes to the stator terminal on the alternator. its not broken and it is connected.

it is wired as follows.

voltage regulator terminal f to alternator feild terminal.
voltage regulator terminal s to alternator stator terminal
voltage regulator terminal a to alernator battery terminal
voltage regulator terminal i to keyswitch.

thank you for all your help. im 17 and i really hate wiring

 

I am suspicious. Do you have a factory ammeter in the dash that says "D" and "C" or do you have a little battery light in the dash, or a little light that says "gen" or something. I thought most of the later model trucks like yours had the dash with the gauges.

If you do have a factory gauge in the dash, your alternator wiring is not correct. Ford had two different ways they wired it up. Someone has changed something along the way if this is the case. Once we figure out exactly what you have, then we can figure out how to proceed.

 

my truck has a little charge light. no ampmeter. by the way the light worked just fine untill my truck quit charging. since then it has completly quit working. i dont know if this is related to the problem or not.

thanks again for helping.

 

Definitely related to the problem. Since you have the dash light, your system is triggered by voltage on the "I" terminal on the regulator. This signal starts at the keyswitch, and then runs up to the light in the dash. The light in the dash is not grounded. Power from the keyswitch enters one side of the bulb, and exits the other side and then makes it's way out to the "I" terminal. When you turn the key and the alternator is not charging(engine is not turning), the "I" terminal is near ground level, so with the key voltage on one side and the near ground on the other, the light will light up.

When the engine starts and the alternator starts charging, the "I" terminal voltage rises to 12v. This puts 12v on both sides of the dash bulb, and the light goes out. If the alternator system fails for any reason, the "I" terminal voltage will drop and the light will come on.

You are not getting voltage through this system to the "I" terminal. I would verify this at the "I" terminal wire, look the wire over under the hood, and then I would pull the dash cluster and check the connections to it.

 

thanks alot. ill check it out and let you know if i find the problem

 

Welcome to the forum Brian!

Dave,
With this type of charging system is there a resistor bridge so that if the bulb burns out the alternator still charges?
I know the Bosch charging system on my old airhead BMW motorcycle was like this.

 

i pull the dash apart and everything looked ok. i think i might replace the i terminal wire and see what happens. the bulb was not burnt out either

 

Yes, this system does use a resistor around the bulb in case the bulb burns out, it will still trigger the system through the resistor.

To the original poster. It's getting to the point where you are going to have to use your testlight to poke around this circuit while you turn the keyswitch on, checking along the way to see where you are losing the signal. You should be able to take the "I" wire loose from the regulator and ground this wire. When you turn the key on, the dash bulb should light up.

 

i got it fixed. it was the plug in connecter for the wire was corroded. thanks alot for your help. im kinda ticked at the fact that i spent 140 bucks and all it needed was a new connecter.

thanks again.

off topic but how much do you know about the 6.9 diesel. im looking at buying an 85
f-250 with the 6.9 idi diesel. it has 250 000 km and a 4 speed.

 

I used to know nothing about them. Then I bought my 89 with a 7.3 diesel(basically the same engine as the 6.9) and did a lot of research and reading in the diesel forum on this board, and learned a lot.

There has been a diesel craze going on, and some people want to get into it and buy one of these older diesels cheap. Then they find out they are slow(if they do not have a turbo kit) and there are no gee-wiz-bang chips and non of the stuff in the magazines are made for these engines. So be warned if this is what you are looking for, you need to pass on these early engines.

If you are looking for a truck that gets good fuel mileage and pulls a decent sized load, albeit slowly, then you can get good service from it. The engines last forever if they are taken care of. Over 200,000 miles and close to 300,000 miles are not unusual.

The biggest thing about these engines is starting cold. When you go look at this truck, make sure it hasn't been run for at least 8 hours or so. If when you go look at it and feel the engine and it's warm, or it's running when you get there, be suspicious that he has shot ether in the engine to get it started. This is not the end of the world, but it means the engine will need a little bit of work, and that should bring down the price.

 

my dad told me to avoid the 6.9 because the heads had pressed in combustion chambers and they would sometimes fall out of the head and go up and down the cylinder.

im not looking for a fast truck my 85 is my fast truck with a 3.08 rear. im looking for something i can drive every day, pull trailers, off road now and thenm, and get decent milage.

i want it to be reliable and not break down every month. it will be a work truck so i cant afford much down time.

the asking price is $1500 but the 3rd gear shifter fork is broken. comes with some spare body panels. i think $1500 is fair but ill try to get it for $1200