I looked at the number of posts...
alternator wiring
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New User
Joined: Dec 2006
Posts: 13
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From: wills point tx.
alternator wiring
help, lost my memory.
i have an 86 f150 302 efi that wont keep a charge. i replaced the alt, battery and made a new harness that the rats ate. the origional harness had two ten gauge wires comming from the alt to a plastic connector and a single wire comming out going to the solenoid. i did not re-use the plastic juntion as there no wires left to splice onto. i am showing an .08 amp draw with everything off.
any suggestions?
i have an 86 f150 302 efi that wont keep a charge. i replaced the alt, battery and made a new harness that the rats ate. the origional harness had two ten gauge wires comming from the alt to a plastic connector and a single wire comming out going to the solenoid. i did not re-use the plastic juntion as there no wires left to splice onto. i am showing an .08 amp draw with everything off.
any suggestions?
Moderator
Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
.08 amp draw is good.
With the truck off, take your meter and check that plug with the two wires on the back of the alternator. You should have 12v there. If not, you have a fusible link blown.
With the truck off, take your meter and check that plug with the two wires on the back of the alternator. You should have 12v there. If not, you have a fusible link blown.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
You can get the three wire charge plug at almost any auto parts store for under $10.
Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman 85123
Motormite 08622
NAPA VRA400
Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman 85123
Motormite 08622
NAPA VRA400
Thread Starter
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New User
Joined: Dec 2006
Posts: 13
Likes: 1
From: wills point tx.
alternator wiring
thanks for the repiys. I worded my question wrong.what i meant was is almost one amp current draw enough to kill a battery in five days? it charges 14 volts, but if i let it sit five days my battery will be dead.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
You would think 1A*120hrs=120Ah.
But the load remains the same, and as voltage drops amperage increases.
Are you taking your reading at 14V, like just after shutting the truck off?
Are you taking it at a 'normal' at rest voltage of 12.5XX volts?
An automotive battery is "dead" at 10 volts.
No doubt a load like that will kill your truck between weekends.
But the load remains the same, and as voltage drops amperage increases.
Are you taking your reading at 14V, like just after shutting the truck off?
Are you taking it at a 'normal' at rest voltage of 12.5XX volts?
An automotive battery is "dead" at 10 volts.
No doubt a load like that will kill your truck between weekends.
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
Gary,
Welcome to the forum!
It sounds like you have checked the connections and wiring and are receiving good advice from other forum members, but something came to mind.
My son has a 1984 F150 with fully intact charging system. When he had a high-end stereo unit professionally installed, they wired it such that the amplifier [under the seat] is continuously "hot". If left sitting for more than a weekend, his good battery will be pulled down to a point where the engine will not crank.
On his, there is an electrical cable [to the amplifier] with a large inline fuse connected to the positive terminal of the battery. He pulls the fuse when he knows he will not be driving for more than a couple of days and the battery remains fully charged.
Welcome to the forum!
It sounds like you have checked the connections and wiring and are receiving good advice from other forum members, but something came to mind.
My son has a 1984 F150 with fully intact charging system. When he had a high-end stereo unit professionally installed, they wired it such that the amplifier [under the seat] is continuously "hot". If left sitting for more than a weekend, his good battery will be pulled down to a point where the engine will not crank.
On his, there is an electrical cable [to the amplifier] with a large inline fuse connected to the positive terminal of the battery. He pulls the fuse when he knows he will not be driving for more than a couple of days and the battery remains fully charged.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
David,
He joined eight years ago!
Maybe your son needs an relay circuit triggered in run & accy?
He joined eight years ago!
Maybe your son needs an relay circuit triggered in run & accy?
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Lead Driver
Joined: Jul 2009
Posts: 6,477
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From: Sheffield, AL
Excellent suggestion. Thank you!
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Moderator
Joined: Jan 2001
Posts: 57,014
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From: Virginia
Take the negative battery cable off, clip a testlight to the battery terminal and poke the neg battery cable you just took off with the other end of the testlight. If the testlight glows bright, you do have a drain.
Thread Starter
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New User
Joined: Dec 2006
Posts: 13
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From: wills point tx.
yes, i did mean .8 amp draw. I installed a relay into the feed wire that has the draw and it corrected the dead battery problem, but that wire also feeds the ecm memory, and it runs really bad for several start ups. my next step will be to disable the aftermarket stereo, and the factory clock,and check it again. if that fails, i'll disconnect the alternator and see if that is the source. if that dont answer my question i'll start driving it more often! thanks everyone
Moderator
Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
You can pull fuses to check where the draw might be coming from. But if you do have something like a amp connected directly to the battery somewhere you will have to pull that wire off. And you are correct, the alternator can be at fault even though it seems to work ok, and pulling the wires off it will determine if it's the culprit.
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