I have been driving my truck around a little when it is nice out.I got about a hundred miles on the motor now. I have been been driving it during the day so nothing has been running. electrically but the engine electrical. The other night I had to go to the store. Coming home and getting cold, turnt heater fan on, Starting to rain, turnt the wipers on and getting dark turnt the lights on about 10 seconds later truck dies there I am cruising about 55mph and nothing. Pull over and try to start it and barely turns over. Turn everything off and she finally starts. I end up driving home in the dark, in the rain and cold. I now run a hyfire ignition box,Mallory unilite and have an elecrtic fuel pump, but I wouldnt think that would run the battery dead. So I went and bought a 100 amp alternator and a new voltage regulator. At idle with nothing on but engine running the amp gauge shows 0. When I turn the heater fan and wipers on it drops then goes back to zero. when I turn the lights on It drops and almost dies for a split second and is at a negative charge. I have went through all the wiring checked all the connections and am at a lose. Hoping someone on here can help. any help is still help thanks.

 

we need a little more info, what year, motor, trans. just guessing for now, you said the motor is fresh, I assume you painted the block. with that said, take the ground wire off, scrape the paint down to bare metal where it hooks up, and clean the cable before you re- attach it. you are getting enough ground to start and run, but not enough to re charge the battery.

 

1975 Ford F100 2wd 300 six w/3 speed manual. I will make sure that all the grounds are good I am sure I scraped all the paint off, but I will check again. thanks

 

Weak battery, did you make any pulley changes, check voltage at batt, off and running, just a couple more ideas. Thats why I prefer a voltmeter instead of amp gauge, you can see whats going on better.

 

It has more volts off then running at the battery. I checked all the grounds and replaced the one from block to cab. To late to start it up tonight so I will try to start it up tommorow.

 

Recheck all of your grounds. The first one being the negative cable from the battery to the block. It will allow you to drain the battery but will not allow it to take a charge.

edit never mind skimmed past the other posts... maybe the altenator? pull the battery cable off while it is running and see if it stalls

Jim

 

make sure all the wires going into the voltage regulater are conneccted, and in good shape, same with the connections to the alternator. if all good, change the voltage regulater. was there a chargeing problem before the new motor?

 

You've proved it isn't charging with voltage test. Check the stator lead on alt for voltage. Should have it as soon as you turn the key on. If not, work your way back. Regulator needs grounded before plugging it in, or you can smoke it. Preferably grounded back to alt case.

 

I started my truck up tonight. no change. I noticed the wire from the stator was hot (hot enough to melt the electrical tape about 3 inches back). and all the wiring between the alternator and voltage regulator was warm, dont know if that is normal or not. I tested for voltage at the stator and no voltage. does the alternator need a ground coming off of it? I hooked all the wires back up the way they were before new motor so it had a ground wire, then when I stripped all the electrical tape back the ground had been cut and and taped over. When truck is running battery tests at 11.9 volts when I rev it up to 1500 to 2000 rpms it says 12.2 so there is some kind of charge but not what is suppose to be. I got this truck from my brother about 3 years ago and he is not by any means a electrical genius. he had radio wired into brake switch power. so I dont know what he might of wired crazy. I am still pulling and fixing wires as I go. thanks for any help.

 

A good batt should read about 12.5V at rest. About 14.5 with alternator charging. You should have voltage on the field with it running as that what starts the alternator charging. Wires shouldn't be hot, means high resistance in the wire, connection, or short to ground. The ground wire on alt. is usually connected to a screw that holds a wire loop/holder on the alt. Make sure the volt. reg is grounded using your ohmeter function. As I said before, if it is not grounded before plugging in the wires, it can burn it up. The screws holding it to the fender or whatever, normally give it a ground but easily checked. Same with the alternator mounting brackets. All good as as long batt. neg goes to the block, block to frame and ground from engine to firewall. Never have too many grounds.

 

May be a little diff, can't remember what year this is, but should help checking voltages.

 

PROBLEM FIXED!!! I pulled all the electrical tape off the wires between alt. and volt reg. and noticed there was a ground going to the alt. and that it was hooked up to the stator and not the ground. stupid I know but it is fixed and charging. thanks for all the help. I hooked it up the same way my brother had it and would have never thought it was wrong. I called him and he always wondered why it never charged the right way. If he wasnt lying it has been that way for 25 years and he had only replaced the alt. and voltage regulator 1 time. thanks again , case closed.