Battery Drain
Thread Starter
|
Freshman User
Joined: Mar 2008
Posts: 26
Likes: 0
From: Sanford
Battery Drain
I have a 92 f150 4.9 l 5 speed and if I leave my truck sit for a day without starting it the battery will drain down to about 8.50 volts and won't start. I know where stuff is but not sure what to check. Does anyone have any ideas? I know that there is nothing being left on in the truck. Help if you can please.
Logistics Pro
Joined: Apr 2011
Posts: 4,744
Likes: 5
From: Earth
even if nothing is "on" you have something thats causeing the drain, either by always being constent on (hot) or that is shorted compleating the circut draining the battery, do you have any mods to this truck of yours, have you installed any thing that can be left on all times? is there ANY thing thats on a circut with NO switches? IE do you have a GPS plugged in the power port which is always hot that you leave running (charging battery when "off") that remains plugged to the power port?
if so things like that could be the cause, so if we know what mods if any were done we could at least start somewhere, did you add a train horn/air horn? they are items that could be possibilities if added in.
also check the key is fully "off"IE it isnt in ACC mode or run mode
if so things like that could be the cause, so if we know what mods if any were done we could at least start somewhere, did you add a train horn/air horn? they are items that could be possibilities if added in.
also check the key is fully "off"IE it isnt in ACC mode or run mode
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
With the engine off and a fully charged battery disconnect the positive cable from the battery and see how big the spark is.
Connect an ammeter in line and see how much it is drawing, or use an inductive ammeter -around- the battery cable if you have one.
First, try unplugging the alternator. if the draw stops the rectifier diodes in the alternator are bad and allowing current to flow to ground.
If you have a second generation alternator (2G...with an external fan on the front) check the condition of the charging plug. (the rectangular one with 2 black/orange wires and 1 white & black)
If it's melted, or has ANY signs of heat discoloration replace it with a new harness pigtail before it sets your truck on fire.
NO JOKE!
Any GOOD autoparts store should have one of the following in stock for under $10.
Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman/Motormite #85123 / 08622
etc.....
Connect an ammeter in line and see how much it is drawing, or use an inductive ammeter -around- the battery cable if you have one.
First, try unplugging the alternator. if the draw stops the rectifier diodes in the alternator are bad and allowing current to flow to ground.
If you have a second generation alternator (2G...with an external fan on the front) check the condition of the charging plug. (the rectangular one with 2 black/orange wires and 1 white & black)
If it's melted, or has ANY signs of heat discoloration replace it with a new harness pigtail before it sets your truck on fire.
NO JOKE!
Any GOOD autoparts store should have one of the following in stock for under $10.
Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman/Motormite #85123 / 08622
etc.....
Thread Starter
|
Freshman User
Joined: Mar 2008
Posts: 26
Likes: 0
From: Sanford
First off thanks for the help. @ Jaime the only aftermarket item is a CB and is hooked to I beleve the radio circuit that shuts off with the truck. I have recently put a new alternator on but this problem was happening before that. @ phoneman I park the truck on flat groung but I did chek the light under the hood and the bulbs not in it. I am going to try and do an ammeter test. To add to the situation. I went out this morning and turned the key on I had no start-up lights or guages move. It was light I had no power on the dash. I unhooked the Negative cable and when I hooked it back up the dash was working. Strange!!
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
The battery was recovering while you had the cable disconnected.
It doesn't take much. Lead acid batteries are very robust.
If it is the plug a new alternator will not fix it.
FWIW, most alternator rebuilders will not warranty without your replacing that plug.
Many of the better rebuilders include one in every box.
It doesn't take much. Lead acid batteries are very robust.
If it is the plug a new alternator will not fix it.
FWIW, most alternator rebuilders will not warranty without your replacing that plug.
Many of the better rebuilders include one in every box.
Hotshot
Joined: Jan 2008
Posts: 13,144
Likes: 11
From: Rochdale MA
A poor mans alt test is to first thing in the am before starting the truck is to feel the alternator, if it is warmer than ambient temp then the diodes ( as Jim had said) are leaking and drawing current.
Trending Topics
Elder User
Joined: Feb 2008
Posts: 797
Likes: 1
From: ohio
Connect an ammeter or dvm between the neg terminal and the Start pulling fuses till you have no draw. Unplug alt, relays ect. Then you will know where the problem circuit is.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Thread Starter
|
Freshman User
Joined: Mar 2008
Posts: 26
Likes: 0
From: Sanford
Ok, I hooked up an ammeter and I have a 3.89 draw. I unhooked the fuses and relays both inside and outside the truck. the only ones that made a difference was the fuse which controls the clock memory. i unhooked everything in the engine compartment and the stuff under the dash that i could reach, all with no change. I hooked the battery back up and the dmm is just slowly counting down?????????????
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Disconnect the black/orange charging wires at the starter solenoid and see if it stops.
The solenoid itself could be shorted to ground through the mounting plate but IME that is very rare.
The solenoid itself could be shorted to ground through the mounting plate but IME that is very rare.
Thread Starter
|
Freshman User
Joined: Mar 2008
Posts: 26
Likes: 0
From: Sanford
There is a doubloe white wire on the starter soliniod that runs to the headlights and over to the other side. if I hook the ammeter to that connector to positive post that I believe is the draw. the black and orage wire made no dofference. I left the negative terminal off so it would start this morning.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Have you traced those white wires and looked for frayed or chafed areas that could be shorting out?
I only have schematics through '88 so I can't say with any certainty where those wires go.
I only have schematics through '88 so I can't say with any certainty where those wires go.