Hey guys I have a '97 f-350 and have a short somewhere that will kill both batteries in a matter of hours. When I try to hook up the positive cable I get a really good arc and a bit of 'melting' on the battery post untill it is firmly on.
When I start the truck up the alternator guage reads low unless I rev up to 1500rpm. The truck had a flat deck on it but it is removed right now and the alternator is new. The problem was there before I took the deck off so I know I didn't rub a wire. I had the tranny rebuilt and a few other things but nothing electrical that I know of. Is there any ways I can test wires to eliminate causes of this problem. I suck at electrical....

 

alot of times you can pull fuses to find what circuit its on that the problem is on.

check your batteries you could have one that is internally shorted out causing both of them to drain. you can test with a megohm meter but REMOVE PCM, GEM, COMPUTER, AND RADIO!!!!!

best off just searching through the wire loom and pull your fuses. with the trans being done recently i would start checking around that first.

 

I will try the fuse trick, simple and straight forward, (why didn't I think of that) but I am sure it's not the batteries because I bought 2 new ones and it never changed the short.
A little history may help understand my problem better too.
I posted a couple weeks back in the 67-72 forum that I traded my 71 for this 97 diesel. The guy I got it from used to use this truck as a maintenence truck in the oil field. The shorting problem happened after one of the few times it ended up in the shop for repairs. After it came back the operator of the truck would have to disconeect the batteries each evening when parking and then reconnect in the morning to go to work. The truck never shut off each day it was worked. The flat deck was sold and the truck came to me with the deck from another truck which I haven't put on yet because I want to find this wiring problem first. When the guy I got it from and I tried to fire up the truck when I got it, after turning over for about 20 seconds we found the solenoid on top of motor was incredibly hot, but the engine hadn't even run yet.
Can a solenoid fail like that? Also I believe the short to be before the ignition because the key doesn't have to be on to drain my batteries. I suppose if the tranny were out and a wire got pinched or rubbed it could very well be the problem.
I'l keep looking.....

 

Sounds like the GPR maybe has welded its contacts together internally, causing the glow plugs or the Inlet Air Heater to be drawing current all the time.

It sounds like you are in an area that likely is going to start getting VERY cold shortly, so you need to get this fixed rather than simply disconnect them.

Find that relay that got hot on the top of the engine.

Take the two small wires off of it. Be sure to remember which goes where when you put them back on. Wrap tape around the ends, as one of them will still have 12volts on it as soon as you connect the batteries. Now, connect the batteries. Is the heavy current drain there now? If not, you're half way to finding your problem.

If the current drain IS still there, you HAVE found the problem, it's the Glow Plug Relay (GPR), and the internal contacts have welded themselves together, thus it's always on, and with a pretty healthy current drain, too. You know how to fix this.

Back to if the current drain ISN't there. Measure the ends of the wires and find the one with 12 volts. Re-connect that wire to the relay. Turn on the ignition key. You should still not have the large drain. Wait at least three minutes with the key on and the batteries connected.

Now comes the hard part. First, measure with an ohmmeter to see if this other wire is a ground. It shouldn't be, at least not after three minutes or so, as the glow plug timer should have "timed out", eliminating the ground on that wire, causing the GPR to cut off power from the glow plugs. If you still have a ground, shut off the key and disconnect the batteries. It's time to find a short to ground in that wire, OR worse, a perminantly grounded signal from the computer that drives it, which I believe is the PCM, Powertrain Control Module. Someone with factory wiring diagrams will correct me if I've got it wrong. First thing it to eliminate a shorted output from the module. Disconnect the plug that has the GPR wire to see. If you've STILL got a ground on the wire, trace the wire for chafing against a ground point for worn-through insulation.

If it's a bad PCM, I think I'd just wire a momentary-contact push-button switch in the cab to this wire and ground, and manually control when the glow plugs come on. Manual control of this circuit is something that I'm considering doing to mine, anyways.

Hope I haven't confused you and have given you a place to start troubleshooting. I also hope I haven't steered you wrong about the ground logic involved in the GPR.

Once again, if I have steered him wrong PLEASE, somebody jump in here. (I GOTTA' get those wiring diagrams, da##it!)

Pop

 

Well after I got home from camp this stint I pulled each and every fuse one at a time and tried to reconnect my battery. Each and every time it would arc pretty good. So I pulled the 2 smaller wires off the relay on top of the engine(looks like a starter solenoid) and still had the arc. I guess it's time to start buying parts. My question is if it is the glow plug relay, and the glow plugs were replaced not long before the truck was parked, would the glow plugs be hooped by pulling a charge all the time untill the battery dies? There is snow on the ground pretty good now so I get to work in the stuff.....Yippee!!!

 

Well broke down and changed the glow plug relay. When I hooked up the batteries I had no sparks or arcing that used to melt the battery post. I will leave the batteries connected overnight and see if they held a charge. If they did well Springerpop gave me some real good advice that worked. Thanks

Adam

 

He does that from time to time.

 

dang....i wish i had seen this sooner. i recently went through that, turns out, i had wired my GPR backasswards....batteries kept dying even when running, and the alternator heating up fast. took it to the shop, they found i'd wired it backwards, back to normal. now, as to why i didn't ask here before i took it to the shop....WHO KNOWS, i confuse myself a lot ... glad ya got it figured out though!

 

Well day 3 of -10* weather and still holding charge just fine. GPR was definitely the problem. Thanks guys, won't forget this one!!

Now for the rest of the problems.....

Adam