Hey guys,
I just bought a 74 F250 4WD, With an old FE block, for a smoking deal, but now im figuring out why it was such a cheap truck...I lost all electrical power the other day when I was driving, pulled it to my job and started digging into it. Well it looked like the truck was running just off battery power. I replaced the Alternator, Voltage regulator, but the truck is still having issues. If I remember correctly, I should be getting around 13-14 volts with the truck running? Because I am only getting 10-12 volts and power drops, I feel like there is a wiring issue some where. What is your thoughts? Any help would be most appreciated

 

Yep.. Sounds like an electrical problem.

Inspect the wiring and make sure it is hooked up correctly and for any broken wires.

Btw, It would not be unheard of to receive a bad alternator from auto retailers. Just because it is "new" doesn't mean it actually works. The originally installed alternator tested bad, right? Are you sure the battery is OK?

 

assuming all your new parts are good, it's possibly wiring...

link to much of the associated wiring:
http://fordification.net/tech/images...aster_2of8.jpg

 

There is a post on here somewhere to troubleshoot this. Charging system troubleshooting I think. I fixed my problem with it. In general though need to know if you have dummy lights or gauges as things are wired different for each. In mine the voltage regulator was not getting juice to turn it on on the s terminal. I have gauges though. If you have the lights I don't have exp with those.

Step one. Voltage with engine off. Baseline v take at the batt. Step 2 voltage running no load, step 3 voltage running with lights an heater on. Should get about 12.5, 14.5, 12-14. If this is not the case we need to check the wires at voltage regulator. With gauges you should have bat voltage on a, with key off nothing on s with key in run battery volt on s. A comes from battery s on gauge cluster type comes from ingnition switch or can be from fuse box. To do a quick test on alternator you can jumper between a and f pins on wiring harness to voltage regular. Do this quick you should get 15ish volts with engine running. If so all ok with wiring and alternator.

If you have a good alternator, good wiring, voltage on a and s terminals and no field voltage probably need new voltage regulator.

Just to help the f signal turns your alternator on and off. Oh and the labels are on the voltage regulator a s f I. It is on your passenger fender well by the starter solenoid.

You may need to do some wiring checks too, there are fusible links one may have blown.

Hope this helps
-k

 

Welcome to FTE

With any "new" truck there will be some things to get acquainted with. If you bought it cheap that's good, because they ain't necessarily cheap ever again, haha. The one thing that all old trucks seem to have in common is corrosion and rust and therefore high resistance electrical connections. It will just keep getting worse and worse till nothing works anymore. Everyone is probably familiar with cleaning off battery posts and terminals, but there are dozens more connections that are (mostly) just as important and will eventually need the same routine. Try to stay out in front of that saves a ton of aggravation. Trust me. An electrical connection can't be too clean or too well grounded. Every thing on the truck depends on it, from spark plugs to tail lights.

You are going to have to have a strong work light and inspect your truck wiring (among other things) from stem to stern, for some reason people like to really hack up wiring. Try not to compound your current electrical problems, keep the battery on a trickle charger and keep topped off, replace the ground and battery cables now. They start to act like resistors and rob current.

You can do a lot with just a test light and a voltmeter if you know what you're looking for. Check out the YouTube videos for "Voltage Drop Testing" and alternator tests and you'll see what is involved. Real simple stuff. A Ford Truck Shop Manual is a good investment, they made one for your truck and will be invaluable.

 

Yes, the old one tested bad, and the battery tested good. I have a feeling my "new" alternator is bad, im going to go have it bench tested monday.

Thank you it did help quite a bit actually. With full load on the battery, I only get about 11 volts. So I followed your instructions how to test my wiring. everything was fine until I Tested the A and F connection, It only read my battery voltage, no where near 15 volts. Thats why I am starting to think it may be another bad Alternator?

Haha, yea I can already feel my pockets draining. I have massive plans for this truck if I can ever get some of the small stuff worked out

 

Sorry for a double post, but the alternator tested good. So, I went through a lot of the wiring today, and couldnt find anything major. I did notice though that my alternator gauge wasn't working...would this play a part in my charging issue?
Thanks In advance

 

I am assuming this is a charge discharge analog gauge. They never seem to work or tell you anything and in this configuration shouldn't affect your charging issue. The indicator gets its voltage from a piece of wire in you alternator harness called a shunt. One side of the gauge is connected on one end one on the other. It "detects" the voltage drop across this known resistance wire and tells you if it is charging or discharging. You could cut those wires and have no affect on your charging system.

Seems more like you may have a wiring issue.

If you have the ability to test for continuity (resistance) ensure the following
The alternator charging output has continuity to the battery + side. It does this in a long path, mine goes to the fuse block and back, but they should be connected. There is one or 2 fusible links in there to check.

The stator on your alternator goes to your choke, only your choke. This has no affect on charging.

The field terminal goes to the f terminal of the voltage regulator.

The case should be grounded through the block and you should have continuity to the negative side of the battery.

There are no other alternator connections. Essentially 2 wires does it. Double check that you are on the correct terminals of the alternator. On mine two are close together at 12 (output) and 1 o'clock from the front and one is at 9 o'clock.

Wiggle the wires wile you do this make sure it is a good connection.

Hopefully this helps, good luck.

 

subscribed for future

 

Well, I finally caved and took it to a local shop. Turns out I was missing a wire that runs to the coil from the voltage regulator. Truck runs all fine and dandy now.

Thank you all for your help!

 

Glad you solved your problem. Could you explain were and to what each end of the wire runs. V regulator has 4 terminals I a s f the coil has 2 + and -. Which terminal will help others. Thanks!

 

to the coil?!