The Ford Barn

coilover · 07-29-2010, 09:30 PM

Have an all original 40 pickup that on it's own decided to run the battery dead every night. I don't need a volt meter to check it because it makes a good spark when a battery cable is scraped across a battery post. Here's what is disconnected: voltage regulater, horn relay, generator, brake light switch, head light switch, ignition switch, voltage reducer, and the solenoid was disconnected and a jumper run to the main feed wire. All the wires were removed from these and are hanging in the air. The harness is new from about two years ago and went that long with no problems. I think it must be a short within the harness because I have checked every inch of it all the way to the tail lights and there is no places that rubbed against anything and nothing pointed that could poke into it. Any ideas? Since every thing is disconnected I'm about to hook a 12v battery to it and see what smokes.

PeteVS · 07-29-2010, 09:39 PM

How old is the battery? Batteries have been known to develop internal shorts. Does the battery go dead if it's disconnected? (You should have one of those green knob thingies on the car so you can easily disconnect the battery overnight.)

Just re-read your post. Scratch what I said above. Almost everything in the harness should be "hot" polarity. If you're getting a circuit from "hot" to ground, there's gotta be something ground touching one of the wires. Double re-check for a trim screw or something getting into the harness. Does the truck have a dome light? If so, I'd call that a possibility.

George/Maine · 07-30-2010, 05:02 AM

I guess you just keep disconnect till you find it.Some thing to check.I just rewired my car and taped all wire to rear together.
2 tail wires,stop,gas gauge,marker,elcctric fuel pump,check under dash. floor switch for head lights,Take the main wire off solinode that should kill every thing.

Hamtown Al · 07-30-2010, 07:27 AM

Regardless of your other problems, I would install a heavy battery disconnect switch in the hot cable from the battery and put the switch within reach INSIDE the vehicle. I avoided potentially burning my pkp up by being able to quickly turn the battery connection off while the vehicle was still coasting to a stop. The other day the battery disconnect switch saved the day on another pkp when the starter solenoid hung and the starter remained engaged after it started. Turning the key off had no effect! Definitely include an easily accessable disconnect switch in every vehicle. I often put them on the floor near the front of the passenger seat. Good luck with your other problem. Al

jdl · 07-30-2010, 03:55 PM

With everything turned off, disconect the ground cable from the batt. then rub or touch the cable to the post, if it sparks you have a short, or switch on, or problem somewere, it should not spark if everything is good.

Rustyspokes · 07-30-2010, 06:35 PM

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Coilover... Do you have a dashlight up underneath that is switch operated, I bought a 34 last year and there was a switch for the dash light and it was still hot when the car was off this switch was " stuck on" and drained the battery , I have rewired with a new harness..

gmc1941 · 07-30-2010, 11:25 PM

With everything disconnected as jdl said, you should have no spark. The other thing you can do if you have a multivolt meter put in series with the cable you disconnected. That means remove the cable and attach the meter to the and to the terminal you remove it from. set the meter for amps. you should read Zero. I you read anything you have short or draw on the battery. If don't have a meter find the smallest fuse less the an amp and put in series and see if it pops. Don't rely on the spark that your getting from the battery. A 6volt battery that is down to 3 or 4 volts will spark. Good Luck

coilover · 07-30-2010, 11:57 PM

Thanks all, I located it by running a short finder, which I think is a fancy version of using a compass, along the harness. At a splice where two wires were forked off of one there was a single strand that hadn't made it into the sleeve to be crimped into place. With time and vibration it acted like a needle and worked it's way through the insulation till it contacted the firewall under the triangle shaped plate that covers the main wiring harness on the engine side of the firewall. I'm surprised that it could carry the amperage to drain the battery without burning in two even though it is a heavier strand. I do have just about every tool imaginable (it's a disease) so I was completely baffled. Thank you again; Evan

ken ct · 07-31-2010, 12:19 AM

Glad you found it,they can be tricky.Good job. ken ct.

07-29-2010, 09:30 PM	#1
coilover Member Join Date: May 2010 Posts: 33	40 pickup voltage drain Have an all original 40 pickup that on it's own decided to run the battery dead every night. I don't need a volt meter to check it because it makes a good spark when a battery cable is scraped across a battery post. Here's what is disconnected: voltage regulater, horn relay, generator, brake light switch, head light switch, ignition switch, voltage reducer, and the solenoid was disconnected and a jumper run to the main feed wire. All the wires were removed from these and are hanging in the air. The harness is new from about two years ago and went that long with no problems. I think it must be a short within the harness because I have checked every inch of it all the way to the tail lights and there is no places that rubbed against anything and nothing pointed that could poke into it. Any ideas? Since every thing is disconnected I'm about to hook a 12v battery to it and see what smokes.

07-29-2010, 09:39 PM	#2
PeteVS Senior Member Join Date: May 2010 Location: FP, NJ Posts: 2,828	Re: 40 pickup voltage drain How old is the battery? Batteries have been known to develop internal shorts. Does the battery go dead if it's disconnected? (You should have one of those green knob thingies on the car so you can easily disconnect the battery overnight.) Just re-read your post. Scratch what I said above. Almost everything in the harness should be "hot" polarity. If you're getting a circuit from "hot" to ground, there's gotta be something ground touching one of the wires. Double re-check for a trim screw or something getting into the harness. Does the truck have a dome light? If so, I'd call that a possibility. __________________ Don't never get rid of nuthin!

07-30-2010, 05:02 AM	#3
George/Maine Senior Member Join Date: May 2010 Location: Mid coast Maine Posts: 1,878	Re: 40 pickup voltage drain I guess you just keep disconnect till you find it.Some thing to check.I just rewired my car and taped all wire to rear together. 2 tail wires,stop,gas gauge,marker,elcctric fuel pump,check under dash. floor switch for head lights,Take the main wire off solinode that should kill every thing.

07-30-2010, 07:27 AM	#4
Hamtown Al Senior Member Join Date: May 2010 Location: Smithfield, Va Posts: 822	Re: 40 pickup voltage drain Regardless of your other problems, I would install a heavy battery disconnect switch in the hot cable from the battery and put the switch within reach INSIDE the vehicle. I avoided potentially burning my pkp up by being able to quickly turn the battery connection off while the vehicle was still coasting to a stop. The other day the battery disconnect switch saved the day on another pkp when the starter solenoid hung and the starter remained engaged after it started. Turning the key off had no effect! Definitely include an easily accessable disconnect switch in every vehicle. I often put them on the floor near the front of the passenger seat. Good luck with your other problem. Al __________________ 36 Fords Rule! Visit at www.36fords.com.

07-30-2010, 03:55 PM	#5
jdl Senior Member Join Date: May 2010 Location: California Central Coast Posts: 931	Re: 40 pickup voltage drain With everything turned off, disconect the ground cable from the batt. then rub or touch the cable to the post, if it sparks you have a short, or switch on, or problem somewere, it should not spark if everything is good.

07-30-2010, 06:35 PM	#6
Rustyspokes Senior Member Join Date: May 2010 Location: West Coast Canada B.C. Interior Posts: 333	Re: 40 pickup voltage drain Sponsored Links (Register now to hide all advertisements) Coilover... Do you have a dashlight up underneath that is switch operated, I bought a 34 last year and there was a switch for the dash light and it was still hot when the car was off this switch was " stuck on" and drained the battery , I have rewired with a new harness..

07-30-2010, 11:25 PM	#7
gmc1941 Senior Member Join Date: Jun 2010 Location: Palatine, Il Posts: 486	Re: 40 pickup voltage drain With everything disconnected as jdl said, you should have no spark. The other thing you can do if you have a multivolt meter put in series with the cable you disconnected. That means remove the cable and attach the meter to the and to the terminal you remove it from. set the meter for amps. you should read Zero. I you read anything you have short or draw on the battery. If don't have a meter find the smallest fuse less the an amp and put in series and see if it pops. Don't rely on the spark that your getting from the battery. A 6volt battery that is down to 3 or 4 volts will spark. Good Luck

07-30-2010, 11:57 PM	#8
coilover Member Join Date: May 2010 Posts: 33	Re: 40 pickup voltage drain Thanks all, I located it by running a short finder, which I think is a fancy version of using a compass, along the harness. At a splice where two wires were forked off of one there was a single strand that hadn't made it into the sleeve to be crimped into place. With time and vibration it acted like a needle and worked it's way through the insulation till it contacted the firewall under the triangle shaped plate that covers the main wiring harness on the engine side of the firewall. I'm surprised that it could carry the amperage to drain the battery without burning in two even though it is a heavier strand. I do have just about every tool imaginable (it's a disease) so I was completely baffled. Thank you again; Evan

07-31-2010, 12:19 AM	#9
ken ct BANNED Join Date: May 2010 Location: stratford,ct Posts: 5,971	Re: 40 pickup voltage drain Glad you found it,they can be tricky.Good job. ken ct.