The truck:
1990 F150 Custom / 4x4 / Manual Transmission / I-6 300 4.9 liter / Fuel Injected

I have a new battery and recently my battery has been getting drained in 24 hours to only 1 volt. (This has happened twice after having the battery checked and fully-charged.

Does anyone have advice on what could be drawing power? Nothing has been left on and the truck is stock with no AC, power windows or door locks. I have a voltage meter so maybe I could start from the battery and work to ???

Thanks!
Nabor J

 

Just for kicks have you checked to see if the glove box light is staying on?

 

We should really do a sticky on how to diagnoses a current drain. We get that as much as idle surge and how do I make the truck go faster with less fuel. Anyway the first step in current drain is check your battery connections and grounds. Then remove the battery cable and connect an amp meter in line between the battery and power cable. ( or use a clamp on amp meter if you have one ) If you have a drain you will read amperage. Remove fuses from the fuse box one at a time until the reading drops to near zero. This will tell you what circuit is drawing power. Now you can look for stuck switches, grounded or shorted wires etc. in that circuit.

 

Great tips. When checking amps between the battery and the power cable, what reading should I get? Arrgghhh. This truck has been driving me nuts. I posted awhile back that the wrong computer is in the truck. I have the new (correct) one, so I think I'll start by putting the right one in and starting the diagnosis from there.

 

Hi nabor j,
Anything that has a memory (radio, clock, etc), will draw power with the ignition turned off. Even the engine computer has a memory, and will draw power when the ignition is off.
I see people leave their headlights on when going into a store, knowing they will turn themselves off. That is hard on the battery too.

 

Today I installed a new computer since the previous was was the wrong one. In tandem with my electrical woes, I hoped for the best. After installing the computer, I went for a 10 mile test drive on town roads and the highway so I could see how the truck would respond at varying speeds and shifting. All went well until I got within one mile of my house. I was nearly home when all of a sudden I noticed the tachometer was reading 5-6,000 RPM's and the warning lights on the console all flickered (such as Rear Anti-lock, Check Engine, Etc.) I was no where near 5-6,000 RPM's, more like at 3,000 when all of a sudden the truck stopped running. I tried to start the truck, but got the famous "dead battery clicking sound." Next I checked voltage on the battery and it read 10.33 volts. I did the check with no lights on, the door closed, etc. so I was sure nothing was drawing power (that I could control.) I had someone jump start me and I was able to drive home, but the truck died just as I parked it. I checked the voltage again and it read 9.7 volts.

Any thoughts / suggestions? I'm guessing it might be the alternator? I left the battery connected to the chassis and I'm going to check the voltage for the next few hours to see if it drops. If it does, that will confirm something is drawing power and I will need to do more tests, but what stumps me most is why did the truck die while driving it.....alternator?

Thanks for your feedback!

 

Today I installed a new computer since the previous was was the wrong one. In tandem with my electrical woes, I hoped for the best. After installing the computer, I went for a 10 mile test drive on town roads and the highway so I could see how the truck would respond at varying speeds and shifting. All went well until I got within one mile of my house. I was nearly home when all of a sudden I noticed the tachometer was reading 5-6,000 RPM's and the warning lights on the console all flickered (such as Rear Anti-lock, Check Engine, Etc.) I was no where near 5-6,000 RPM's, more like at 3,000 when all of a sudden the truck stopped running. I tried to start the truck, but got the famous "dead battery clicking sound." Next I checked voltage on the battery and it read 10.33 volts. I did the check with no lights on, the door closed, etc. so I was sure nothing was drawing power (that I could control.) I had someone jump start me and I was able to drive home, but the truck died just as I parked it. I checked the voltage again and it read 9.7 volts.

Any thoughts / suggestions? I'm guessing it might be the alternator? I left the battery connected to the chassis and I'm going to check the voltage for the next few hours to see if it drops. If it does, that will confirm something is drawing power and I will need to do more tests, but what stumps me most is why did the truck die while driving it.....alternator?

Thanks for your feedback!

 

Get it started again and check what voltage your getting at the battery with it running. Could be an alt...electronics can act funny when voltage is to low.

 

And a shorted out alternator with drain a battery also. When you do the voltage test, test it at the battery and also on the back of the alternator to see if it's the alternator or a wiring problem.
You should have at least 13.5 volts with the motor running and lights and heater on. That would be about the same as running a load test on the alternator

 

I'll need to jump start the truck to get it started again so I can do that test....thanks for the advice.

I just did a voltage check now that a few hours have gone by. (The truck still won't start.) At the battery, I am getting 9.7 volts, so not a lot of loss since I last checked it. BUT, when I disconnected the ground wire from the battery, the voltage meter read 7.3 volts. Hmmmm?

I'm living a nightmare with this truck. First a bad computer, now this!