Dead Battery...again and again......
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New User
Joined: Jul 2003
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From: Garner, NC
Dead Battery...again and again......
I have a 1988 Ford F-150 XLT Lariat. Recently I've noticed that everytime I drive the truck and shut it down, I come back to a dead battery.
I replaced the battery and alternator. When the truck is running it's pumping out about 16Volts or so.
When I disconnect the negative battery cable and run a light between the post and the cable, it lights. Obvioulsy something on the truck is draining my juice.
I pulled every single fuse out of the driver's side box and none of them made any difference. The light stayed on regardless of what fuse/relay I pulled.
I don't have the original owners manual so I don't know if there are other fuses that I haven't been able to pull to find out what is going on. I'm tired of popping the hood and disconnecting the negative terminal every time I park the truck so I know it will start the next time I need it to.
Any help for tracking down this problem will be greatly appreciated.
Is there another fuse box that I don't know about? What else could be draining the battery?
Thanks all.
Pete
I replaced the battery and alternator. When the truck is running it's pumping out about 16Volts or so.
When I disconnect the negative battery cable and run a light between the post and the cable, it lights. Obvioulsy something on the truck is draining my juice.
I pulled every single fuse out of the driver's side box and none of them made any difference. The light stayed on regardless of what fuse/relay I pulled.
I don't have the original owners manual so I don't know if there are other fuses that I haven't been able to pull to find out what is going on. I'm tired of popping the hood and disconnecting the negative terminal every time I park the truck so I know it will start the next time I need it to.
Any help for tracking down this problem will be greatly appreciated.
Is there another fuse box that I don't know about? What else could be draining the battery?
Thanks all.
Pete
Senior User
Joined: Nov 2003
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From: El Paso Texas
I'm gonna take a stab at this. Being that you can't isolate a current drain on a fused circuit, let's look elsewhere.
16 volts sounds kind of high, even when charging a dead battery. 14.5 would be more realistic, which leads me to say a bad voltage regulator may be both overcharging the battery when running and draining it when not.
I'm not positive about this, but it is one more thing to look at. Obviously something is creating a parasitic loss on the battery.
Any chance the starter solenoid is staying partially engaged?
Good luck and keep us posted on the progress. Having to disconnect the batt every time you stop would get annoying very fast.
16 volts sounds kind of high, even when charging a dead battery. 14.5 would be more realistic, which leads me to say a bad voltage regulator may be both overcharging the battery when running and draining it when not.
I'm not positive about this, but it is one more thing to look at. Obviously something is creating a parasitic loss on the battery.
Any chance the starter solenoid is staying partially engaged?
Good luck and keep us posted on the progress. Having to disconnect the batt every time you stop would get annoying very fast.
New User
Joined: Dec 2003
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I had the same problem with my 1994 F150. Turned out that my hood light was not turning off. It was sticking in the on position and draining the battery over weekends when I was not driving it much. Check the light at night and make sure it is not burning with the hood shut. Take the bulb out for quick fix.
Senior User
Joined: Dec 2003
Posts: 354
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From: Memphis, TN USA
Probably the alternator is back feeding itself.
First, leave the battery positive and negative terminals connected. Disconnect the positive terminal and then connect a 12v test light between the battery positive terminal and the positive cable that you just disconnected.
If the light comes on, then disconnect "all" of the alternator connectors and see if the test light turns off. If the test light turns off then the alternator or the alternator wiring is the culprit.
If the test light does not turn off then disconnect the starter solenoid connections first to see if the light turns off. If the test light does not turn off then disconnect the starter wiring and see if the test light turns off or not.
Aside from the fuse/relay inside the truck, there are other fuse/relay in the engine compartment and try to disconnect one of them at a time.
Car alarm, audio amplifier are also notorious of draining the battery.
First, leave the battery positive and negative terminals connected. Disconnect the positive terminal and then connect a 12v test light between the battery positive terminal and the positive cable that you just disconnected.
If the light comes on, then disconnect "all" of the alternator connectors and see if the test light turns off. If the test light turns off then the alternator or the alternator wiring is the culprit.
If the test light does not turn off then disconnect the starter solenoid connections first to see if the light turns off. If the test light does not turn off then disconnect the starter wiring and see if the test light turns off or not.
Aside from the fuse/relay inside the truck, there are other fuse/relay in the engine compartment and try to disconnect one of them at a time.
Car alarm, audio amplifier are also notorious of draining the battery.
Senior User
Joined: Feb 2003
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From: eastern Ma
I had a friend who plugged his cell phone into the cigar lighter, and left him stranded a few times. He finally got one of those portable jump start units, because he needed the phone left on for work.
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Mountain Pass
Joined: Oct 2003
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From: Cartersville, GA
I had this problem on a 84 T-Bird and it was the voltage regulator. Do you have a fender mounted regulator? If so.....change it. They ground out on the inside and cause the drain.
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From: Remsen, NY
That phone must have been drawing an awful lot of power or the battery must be really bad. The biggest battery I've ever seen on a phone is about 1 amp/hour, which is in the hundredths of what a car battery stores. And most phones make 1ah last days.
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Joined: Dec 2003
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I had this same problem recently on my '94 and I agree with an earlier response. The culprit is usually something like a light under the hood or in the glove box that is not shutting off properly. My particular problem was that the wires running to the now missing radio were not properly taped and were causing my accessories (ie fan, wipers, ac clutch etc.) to stay on after the truck was off. Seperating the wires when putting in a new stereo solved my problem.
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From: topeka
This thread and it's solutions from an archive search come close to my problem.
I have a 91 explorer sport that drains the battery in about 6hrs.
Battery shows 12.98 volts sitting and if i'm doing it right, alt is putting out 14.33 running.
A mutlimeter shows a drain of 5.89 amps between neg bat post and cable with key off
A test light between neg bat post and neg cable is bright. Going thru the fuses under the hood, test light goes to dim when the headlight fuse is pulled. pulling any other fuse will not make dim test light go out.
Pulling either of the plugins off the alt makes the test light go out completely.
A light like a glove box light wouldn't pull that many amps would it?
so i'm ruling out small lights.
My questions are what could be in the head light curcuit that would pull so many amps?
4.0L, 4X4, 5spd, AC, Push button 4X4 engage that doesn't work
I have a 91 explorer sport that drains the battery in about 6hrs.
Battery shows 12.98 volts sitting and if i'm doing it right, alt is putting out 14.33 running.
A mutlimeter shows a drain of 5.89 amps between neg bat post and cable with key off
A test light between neg bat post and neg cable is bright. Going thru the fuses under the hood, test light goes to dim when the headlight fuse is pulled. pulling any other fuse will not make dim test light go out.
Pulling either of the plugins off the alt makes the test light go out completely.
A light like a glove box light wouldn't pull that many amps would it?
so i'm ruling out small lights.
My questions are what could be in the head light curcuit that would pull so many amps?
4.0L, 4X4, 5spd, AC, Push button 4X4 engage that doesn't work
Last edited by shaggymane; Feb 5, 2004 at 04:28 PM.
Junior User
Joined: Jan 2003
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Very simple! The only thing that will drain your battery that quickly would be a light of some sort left on (whether it be a dome light, a hood light...whatever) or the voltage regulator.
Look at night when it's dark if you don't see any lights (under hood, inside... whatever). Change the voltage regulator and be done with it.
Look at night when it's dark if you don't see any lights (under hood, inside... whatever). Change the voltage regulator and be done with it.