Charging headaches
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From: Rocky Point, North Carol
Charging headaches
I have a 77 F-150 4wd with a 400. The engine runs great, but it is not charging. It has to be jumped, and while running, I'm only seeing 10-10.5 volts on my meter. I replaced the alternator, had the battery checked, cleaned the clamps, replaced the regulator, and have sat for the past several hours verifying that I don't have a ground problem. When I pull the neg. cable with the key off, I don't read any voltage between the cable and post. I am about at my wit's end on this one. Also, as soon as I turn the key on, I drop to about 9.5 volts from 12 on my meter. IT's almost like I'm picking up a load or short to ground as soon as I turn the key on. Any ideas???
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From: Rocky Point, North Carol
Just an update... I went back to it for a little while, and tried to jump and crank the truck, with the same results: alternator wasn't charging. Now I have an additional problem: When I switch the ignition on, I get nothing at all, no lights, no guages, and there's no power to the fuse block. I guess I may have burnt up a fusible link??? I'm so mad at it right now, I can't see straight, so I decided to walk away for a while.
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From: Virginia
Yes, you may have burned up a fusible link, and that may be your original problem too. Most trucks have multiple fusible links, some powering the whole truck, and there may be one in the alternator output wire(possibly your original problem). Anytime you are working with the wiring and the battery is connected, and you accidently touch a wire and make a spark, you run the risk of burning out a fusible link.
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From: Virginia
Most of the fusible links are over near the starter relay on the inner fender. To test them, you need to put one meter lead or lead of the testlight to ground, and take the other lead and poke through the insulation on either side of the link. One that is bad will read voltage on one side, and nothing on the other side of the link.
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From: Rocky Point, North Carol
I checked all of the fusible links coming off of the relay, and I even verified them all against the book by color and routing. They all had continuity; and/or power on the load end when they were supposed to. I am really frustrated, because I tried to look into a Painless wiring system, and they now have one that will work on my truck, but Autozone, who is supposed to be a dealer for Painless, can't find the correct one for me, and I can't order it directly from painless. I have tried to get up with them a few times, with no luck at all. I am about at my wit's end with all of it. I do try to avoid doing any involuntary arc welding by disconnecting the battery before I stick wrenches or screwdrivers in sensitive spots. I will go out and triple check all of my fusible links there at the relay. It's kinda sad that I pretty much have the charging system schematics just about memorized because of all of this. If anyone has any more ideas, let me know on this thread, or e-mail me.
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From: Virginia
See if you have any voltage over at the fuse box.
The fusible links feed the fuse box, the headlight switch, and the ignition switch. The fuse box has different sections. The ones that are hot all the time are fed directly by the wire coming from the fusible link. The parts of the box that are hot only in run are fed by the ignition switch, which is fed by another fusible link.
Your fusible links are good, so go ahead and start testing downstream. I am concentrating on the completely dead problem. I assume you still have it?
The fusible links feed the fuse box, the headlight switch, and the ignition switch. The fuse box has different sections. The ones that are hot all the time are fed directly by the wire coming from the fusible link. The parts of the box that are hot only in run are fed by the ignition switch, which is fed by another fusible link.
Your fusible links are good, so go ahead and start testing downstream. I am concentrating on the completely dead problem. I assume you still have it?
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From: Rocky Point, North Carol
Yep. The entire fuse block is dead; both the switched and constant hot wires. You are probably right about the link. I'm working this weekend, so I haven't had a chance to get back to it. Do you know of any other Painless dealers other than Autozone? I've called a couple of different stores, and they all say they can't order Painless products, but they are the ones I'm getting sent to as a retailer. I'm still trying to figure out how I burnt the link in the first place. I know that if I'm bleeding back to ground, or if one of the wires coming off of the relay or alternator is shorting down, that can burn the link, but I checked every one of them thoroughly before I lost power, and didn't find anything. I'm going to start back on it first thing in the morning and try to figure it out. I would really like to just go ahead and replace the entire wiring system, since I had a lot of problems with wiring from the get go. I had to pretty much re-wire the tail, brake, and backup light harnesses. Just had another thought: the truck has a 3" body lift, and the cab and bed weren't grounding well because the spacer bushings, so I ran several jumper wires between the body and frame so that my grounds would be more effective, could that be causing problems?
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From: Rocky Point, North Carol
Update on my last:
I called a buddy of mine who manages one of the Autoclone stores, and he was able to cross the part number on the harness for me, and it was $600. I think I'm going to go that route with it. I am still going to try to figure out the root problem before I put the kit in, so I will hopefully have something tomorrow night.
I called a buddy of mine who manages one of the Autoclone stores, and he was able to cross the part number on the harness for me, and it was $600. I think I'm going to go that route with it. I am still going to try to figure out the root problem before I put the kit in, so I will hopefully have something tomorrow night.
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From: Virginia
The ground jumpers should not cause any problems, and are a good idea. If you suspect a grounding problem, you may want to get a long piece of wire and hook your negative meter lead directly to the battery negative, and then take some readings. If you get a reading like this, but not with your meter lead on the sheetmetal, then you know you have a grounding problem.
You have it narrowed down. You have voltage over at the starter relay/battery +, and in the fusible link area, but not at the fuse box. So the problem is between the fusible links and the fuse box.
One thing I would double check is the fusible links again. The reason is, you might have a marginal connection that under no load looks good, but under load drops voltage. So this time, turn on the headlight switch, and then check the links again. The headlights are dead (correct?), so they will load the wiring down, which will make your fusible link testing more reliable.
You have it narrowed down. You have voltage over at the starter relay/battery +, and in the fusible link area, but not at the fuse box. So the problem is between the fusible links and the fuse box.
One thing I would double check is the fusible links again. The reason is, you might have a marginal connection that under no load looks good, but under load drops voltage. So this time, turn on the headlight switch, and then check the links again. The headlights are dead (correct?), so they will load the wiring down, which will make your fusible link testing more reliable.
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From: Rocky Point, North Carol
Actually, The headlights worked fine before everything died, and I honestly didn't check them afterward. I will find out though. I will use the wire idea to see how much continuity I'm getting to ground through the cab as well. That could definitely cause issues. I did use the tried and true check for ground faults by disconnecting the neg. battery clamp and checking for current between the clamp and post, and got nothing with the swich off. When I flipped the ignition switch on, I got a reading though. I will definitely check the links under load. I have not tried that yet. I would like to get the problem fixed until I order the new harness, so I will be at it in the morning. I will also take some more pictures as well and post them. Thanks a whole lot for all of the advice. I was completely frazzled with it. The previous owner really made a mess of the electrical. His idea of a wire loom was lots of electrical tape, and I've found several burnt wires in the proccess. One other thing I forgot to mention: When I disconnected the old alternator, the stator and FLO wires were reversed on the back of the alternator. I replaced the alternator and regulator. Will that possibly damage anything else?
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okay, more info: I went in and did a little more checking, and I found one of the links failing under load, which was causing my loss of power in the cab. I went ahead and replaced all 4 fusible links, and trried again. It starts with a jump, but still isn't charging. I'm in the middle of working on it, so maybe I'll figure out the problem shortly. I'm still VERY open for suggestions though!!!
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From: Virginia
Check the voltage on the field "F" wire. You should have some sort of reading on it. The amount of the reading will depend on how hard it's charging.
If you want to do another test, take the "F" wire off the alternator and tape it off. Then hook another short piece of wire to the alt "F" terminal. Get the truck started, and then take this "F" terminal wire and touch it to the battery +. This will put the alternator on full output. You may hear the engine load down a little, and the alternator start whining. And you should see the voltage jump way up on the battery terminals.
The regulator puts a varying voltage on the field terminal to control the alt. If the alt works by jumping the "F" terminal to 12 volts, then you know the alternator is working.
If you want to do another test, take the "F" wire off the alternator and tape it off. Then hook another short piece of wire to the alt "F" terminal. Get the truck started, and then take this "F" terminal wire and touch it to the battery +. This will put the alternator on full output. You may hear the engine load down a little, and the alternator start whining. And you should see the voltage jump way up on the battery terminals.
The regulator puts a varying voltage on the field terminal to control the alt. If the alt works by jumping the "F" terminal to 12 volts, then you know the alternator is working.
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From: Rocky Point, North Carol
Will do. I have rechecked everything again. I jumped and started it, and even pulled the plugs for all of the rear lights, since I had to rewire them previously, without any change. Also, the battery won't turn the motor over on its own. I have to have it hooked up to jumper cables, but I had it checked a week or so ago, and it was good. While running, it stays at almost 13 volts for a minute or two, then drops to about 12, and then does a steady downhill slide until it dies. I did some research, and the alternator that goes with the motor, which came out of a 76 Cougar, is rated at 61 amps. I don't see any reason the truck would be using any more than that. I don't have anything extra on it other than guages and a cd player. (No stereo amps or anything) Be back in a minute. I'm gonna try jumping that wire.
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From: Rocky Point, North Carol
FRANKLIN YOU ARE THE MAN!!!!!!!!!!!!!!!!!! I did what you said, and my charging volts immediately jumped up to 16 and change, and when I took it off, I went back to 12. The only other thing I noticed is I'm only getting about 9.5 volts off of the small terminals from the relay. Could I not be getting enough juice to the voltage regulator??? I just replaced the regulator, but I guess I could've fried it anyways. God only knows with the luck I've been having. Thanks so much.