I need some help I've got charging problems in my 76 f250 w/360 no mods. The alt and volt regulator were replaced and the problem still exist even after troubleshootin all wiring fuses and fusible links. This is what the prob is battery will not charge with enginge running above 1000rpm only 12.6 voltsoutput. Read about some guys going to a 1 wir alt. Does anybody know what kind of alt to use and how to hookup and what to do with the wires to and from volt regulator. Any advice drawingins or what ever would be helpful thanks.

 

if the charge system is working at an idle i would suggest that your belt is slipping. this could be because af worn pulleys. if possible put a mark on your alt puley, start the truck and watch the pulley, with luck you will see the pulley slow down as you rev the engine.

 

charge system is not working at idle or with engine reving have tried the belt loose real tight and at man recommened setting which is about 1/2 in deflection in largest part of belt between pullies. That is why I'm thinking about going to a 1 wire alt. I have not tried marking the pulley will do but I have watched the belt it has white writing onit and I dont notice any slipping

 

Do you want us to help troubleshoot the system you have? Or are you tired of messing with it?

You can get one wire alternators to fit. Just check the autoparts stores, the speed shops like jegs and summitracing, and jcwhitney.

 

I really would like to figure out what is wrong with this. I've been throug the charging system a few times. I've ohmed out all the wires from alt and voltage reg and preformed all test that are in chiltons and haynes and test that come with new volt reg. I even took both to have them bench tested again yesterday. Both tested good, again, and I had my battery tested which a I knew was ok. I'm at a loss. The battery does not drain just sitting on the truck. So, there is not a drain. If you have anything new to look at I'd be happy to.

 

Get a meter.

With the truck off, put the negative of the meter on the case of the regulator.

Touch the + of the meter to the "a" terminal of the regulator. You should have 12 volts.

Turn the key to run, but do not start the engine. With the negative of the meter on the reg case, put the + meter lead on the "s" terminal(I am assuming you have a factory ammeter gauge?). You should have 12 volts.

If that is good, then put the neg meter lead on the case of the alternator. Put the + lead on the large "bat" terminal. You should have 12 volts.

If that is good, then start the engine. The battery terminals should have around 14 volts if it is charging. If not, then take a short piece of wire and hook it to the "f" terminal of the alternator. Start the engine and put the meter leads on the battery. Then take the "f" wire you have and touch the end to the battery +. The voltage on the battery should jump up, and you may hear the alternator whining. If this happens, the alternator is good, and we are missing voltage from the reg to the "f" terminal. If this is the case, you may have found the problem earlier in the post when measuring the "a" and the "s" terminals.

If you have a in dash "alt" light instead of the factory ammeter gauge, write back in because we will have to change the "s" terminal test.

 

Thanks for the help first two parts of this test were ok when i jumped from f term to battery voltage shot up I need to get som wire and rewire

 

Thanks again for your help voltag reg turned out to be problem finally had someone at AZ taht knew how to test. replaced and 14.6v when truck is running

 

How do you test when you have the idiot light and no gauge?

 

Testing with the idiot light system

Get a meter.

With the truck off, put the negative of the meter on the case of the regulator.

Touch the + of the meter to the "a" terminal of the regulator. You should have 12 volts.

Turn the key to run, but do not start the engine. With the negative of the meter on the reg case, put the + meter lead on the "i" terminal You should have 12 volts.

If that is good, then put the neg meter lead on the case of the alternator. Put the + lead on the large "bat" terminal. You should have 12 volts.

If that is good, then start the engine. The battery terminals should have around 14 volts if it is charging. If not, then take a short piece of wire and hook it to the "f" terminal of the alternator. Start the engine and put the meter leads on the battery. Then take the "f" wire you have and touch the end to the battery +. The voltage on the battery should jump up, and you may hear the alternator whining. If this happens, the alternator is good, and we are missing voltage from the reg to the "f" terminal. If this is the case, you may have found the problem earlier in the post when measuring the "a" and the "i" terminals.

The parts in bold above are the only change for the idiot light system

 

Thanks. That is just the info I was looking for.

 

What does it mean when you do the KOEO test on the "I" terminal and you only get 4 volts?

 

Is your dash light burning ok? If it is, there may be some voltage drop through the dash light. That is where the "I" wire comes from, the dash light.

 

Yeah, the dash light is bright. I think that my alternator is shot. I get 12 volts when I do the test at the "BAT" terminal on the alternator. Nothing happens when I do the thing with the "F" wire to the battery though. All of this happened after running a local mud bog last weekend. I think maybe there was water and dirt through the alternator one too many times and it finally gave up. Time to dig through the spare parts pile for another one or have this one rebuilt.

 

Yes, the F wire thing should make the alt go full output. That is all the regulator does, is vary the voltage to the F terminal to make it charge more or less.

I think I made a mistake when I said the "I" terminal should have 12 volts with the engine off. The bulb is using most of the voltage to burn, so you will not get the full 12 volts with the engine off.

When the engine starts, and the charging system is working, you will then get 12 volts on the "I" terminal from the regulator. This puts 12 volts on both sides of the bulb, which make it go out after the alternator starts turning.