I have been having problems with my battery draining down when I don`t drive my truck for a couple of days. Nothing is left on at all. It`s not the battery because I can unhook the battery and let it sit for a week and it will fire right up!
I have switched to a heavy duty tractor-trailer 1000 cc amps battery, it has helped a little but not much. Something is pulling it down but I`m lost. Anyone gotta clue?


1988 4x4 ,300 I6
16 in aftermarket crome
rims w/ BF Goodrinch
mud tires,Pioneer cd
sound system w/ L.A.
sounds amp., tinted windows

Does anyone know how I can get all my truck info above w/ my user, signature name?

 

To get your info in your sig click on "settings" at the top of the page. Then click on "edit profile". Scroll down to the signature section and type in whay you want it to say.

As for your battery drain, these can be a pain. On a non-computerized vehicle you install a test light between the negative battery cable and the negative battery post. Then fuses are pulled one by one until the light goes out. If it never goes out the problem is between the battery and the fuse box and you have a possibly nasty job ahead of you. However, your truck is computerized so it isn't as easy as using a test light. It is not uncommon for a test light to come on under a normal electrical load from an EFI vehicle, so the test light is not a real reliable tool for finding the problem. If it's all you've got, try it and see what happens but it may not do the job. The better way is to use a voltmeter (digital or analog will both work) and a 1 Ohm 100 Watt resistor. Install the resistor in series with the negative battery cable and battery, the connect the voltmeter leads across the reisistor. Set the voltmeter to the 10V DC scale (yes, I do mean the voltage scale) and the reading it shows will be the current drain on the battery. This method will handle a constant load of about 7-8 Amps, and a momentary load of maybe 10 Amps. An acceptable current drain is 0.1 Amp or less. Pull fuses until the current drops. There are also some pitfalls in finding battery drains on electronic vehicles that can trap you, but an 88 F150 shouldn't have many of them. Here are a few:

1. Timed circuits that provide power for a certain time period after shutdown or closing the doors. Example: Dome lights that stay on for 10 seconds after the doors shut, anti-battery drain relays

2. Relays that are controlled by a master switch that provide power to other components down stream. Example: Lighting systems in some vans have a master light switch at the front of the van that enable/disable all the interior lights. Even if all the lights are off the relay will cause a drain if the master switch is on.

3. Aftermarket components like radios, alarms, etc. It is probably a good idea to unplug all this stuff first because it is where most problems are found.

4. Worn wiring that allows a low current ground to short to power and backfeed EVERYTHING in the ground circuit. This bypasses the power distribution blocks and can be very hard to find.

I know you said that nothing is left on, but check your dome lights, brake lights, and anything else that is powered with the key off just in case. The door switches on my truck like to come loose and then they don't turn stuff off.

Where are you located? You can probably get some help if you are close to somebody.

 

My 89 F150 started doing the same thing and I traced it down to the fuel pump relay staying picked up after the engine was shut off. I found it by disconnecting the battery ground terminal and then when I would touch it to the battery I could hear a relay pick up and the fuel pump run. I suspect the problem to be in the ignition switch but I haven't fixed it yet so in the mean time I just disconnect the battery when the truck is parked for a couple of days or longer.

 

Nice post, Silver Streak.

I've always hated mystery electrical problems, to the point I'd usually end up at a shop. You said it - they can be a real pain. Now I might try some DIY, after you explain it like that!

Broncr

 

Hi all. thanks to all who helped me with my ride. ive been restoring a 77-F-150 300 6, 3 speed on the tree. Silver Streak, i did the test that you instructed us on and found the shorts that were keeping the battery dead. the bulb lit up and i pulled one fuse at a time, and the light went out when i pulled the fuse to the interior lights. i found that the door switches were rusted, and was draining the juice out everynight. i just unplugged them, and use the light switch only, to turn the dome on.it charges pretty good now. hope this helps others. this truck was in a field for about 4 years here in wash state and endured the rain fairly well, but got to those switches. these units have got to have clean ground wires anywhere you find one. thanks again for the insight.

 

'89 F150 300 FI, the injector cooling fan stays on sometimes all night, so I have to check it after it's been parked for awhile. Still looking for the control switch, but in the meanwhile I just check to see if it's whirring (hard to hear, it's a quiet fan) then rattle the ign key a couple times and it turns off. Much better than finding a dead battery the next day. It is supposed to turn off after 10-15 minutes after engine shutdown according to other posts.