Hi all. I purchased a '65 F100 a couple of months ago for plowing my driveway. It needed a little work but I got her running pretty good just in time for the snow. It's got a 352, 4 speed, 4x4 with a newer Meyers plow setup. One of the previous owners swapped out the alternator for a different one. It doesn't have any wires going to the external voltage regulator. It basically has one wire coming out of the back going to the battery and spliced into that wire is another wire going to the side of the alternator via a plug (red wire). The plug is a two wire plug, one wire being feed like said above and the other wire is a brown wire that is just terminated. I'm assuming the brown wire is the alternator exciter that is suppose to go inside the cab. Anyways, I just put in a relatively new 750Amp battery and after 2 plows, the battery died. I'm assuming that something is wrong with my alternator. When I went through the truck I rewired most of it myself, just cleaning up the rats nest that was under there so I'm pretty sure that the grounds and all connections are good but I never messed with the alternator. I looked at AutoZones website and they say that the alternators for this year truck is a 61 Amp. So I'm figuring a couple things could be wrong:

The current alternator needs an external voltage regulator but it doesn't so it's draining the battery(don't know if this is possible but its a guess)

The alternator is just plain shot

The alternator is just sized wrong for the truck with a plow and plow lights, etc

So, I was wondering if anybody could help me out in figuring this out. Are there any known higher output, internally regulated alternators out there for this application (100-150Amp).

thanks
dirtbikes987

 

Sounds like you have a 1 wire GM alternator on there. Somehow the one wire "tickles" the alternator to charge. It gets power and sends power back thru that one wire. Someone with more experience and an electrical mind can better ( and will ) explain how they work.

Barry

 

one thing I forgot to mention is that 2 times ago I started it, it was fine, cranked over normally and everything seemed normal. After about 15 minutes I noticed that my head lights started to die and the plow would barely raise. I had to go in and eat so I turned the truck off and when I came back out it wouldn't even think about turning over. I jumped it and it started right up, lights worked fine, plow worked fine so I ran it for about another 10 minutes then turned it off and it wouldn't start again. So I took the battery out and charged it for a couple of hours. Last time I ran it everything seemed fine. So, could it be that the alternator is just way undersized and it can't keep up with the load of the lights and the plow. I know most guys run dual batteries if they plow alot. This truck is only used for my driveway so I don't feel like I need to take it that far but maybe that is my problem. As for the one wire GM style alt. I have a 350 in my jeep and so I looked at the alternator on that and on that alt the bat lead goes in back and then the exciter comes out of the one wire plug on the side. So, I'm still confused about the fact that the bat lead on this alt is jumped over to the side plug as well.

 

It sounds like the it is wired wrong and just does not work. I really do not know what you have for an alternator on the truck ie what it fits or the correct wiring for it. If there is a shop that specilizes in automotive wiring they can probally fix it with no problem or tell you how.

 

I'm gonna take a look at the mfg'er of it today and I am going to test to see if it is charging the system or not (voltmeter across bat running just motor, then with all lights and options on). My big question is if there is a HO alt for these trucks.

 

Some of the newer GM 1 wire alternators are wired internally to eliminate that side plug. Somehow they use that one wire to have power go back and forth. It probably go to the alt to get it charging and the once it's charging , reverses direction to charge the battery. If you wanted to, get a late 70's 60amp alt and wire it as it was before. The newer Ford have the regulator on the back of the alt and I'm not sure how they're wired. If you have a electric pump on your plow, it sucks juice like crazy! If so, I'd do the dual battery set up.

Barry

 

you can also find the original alternator and have it insides changed by a shop to put out a lot more 95-110

 

frty7ford, I never heard of that, I'll ask around about that option. Well, I braved the subzero temps today in NY when I got home from work and this is what I found out. I tested the voltage across the battery and at idle it's about 11.8, at high revs it about 14.5ish. All the info that I read said that it should be above 14 at high revs so I'm good so far. Then I turned on all of my lights and the fan and took a reading and it dropped to like 14.2, so I'm still good. Then I managed to raise the plow at the same time and it dropped way down past 11. But once I stopped it came right back up to 14. I was just able to make out a Delco stamp on the back of the alternator so at least I positively know that now. I then remembered that when I got a new wiring kit for my jeep that it had info in it about different wiring systems and how to do it so I looked at an internally regulated Delco system and it seems like my system is hooked up properly minus one redundant wire. It is suppose to have a wire right from the battery to the bat post of the alt, a wire from the +B of the starter selenoid to the bat post of the alt, a jumper from the bat post of the alt to the #1 or #2 plug on the side (don't remember which # it said) and then the other of #1 or #2 is the exciter. So, the only wire I'm missing is the wire from the +B of the starter selenoid to the bat post of the alt. I'm not going to put that in because the battery cable goes to the +B of the starter selenoid so that is just redundant. So, I guess it's just that the alternator is just undersized and can't keep up with the demand that the plow pump puts on it. Time to find a bigger one and possibly redo it so that it has dual batteries. thanks for the help guys

 

bad diodes is my guess.