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

 

Check your starter relay as well as your ignition switch, disconnecting first one and then the other to see if that solves the problem. Does it charge normally while the engine is running? It is also possible you have a short in the alternator.

dn.

 

Common problem with these alternators.

 

I had this problem with my truck before I started ripping it apart to "restore" it.

A few other common problem are the hood light can stay on, and the glove box door light.

There is a pretty easy way to test it, if your not good with a multi meter. Yank a fuse, let it sit overnight, then see if your battery drains. It might take a few nights, but you will find the circuit that has the draw that way!

You can also pull the battery cable and test that way with a multi meter.

 

When you say "pull the battery cable" and test it, how is the test done? Thanks for the advice!

 

Install the meter between the battery post and cable, then pull fuses one at a time to see which one (if any) stops the flow of current.

 

Pull the negative cable off. Put a multi-meter between the terminal on the battery and the cable. Set the meter over to amps and you should get a reading. That's the amount of current being drawn by whatever is shorted out. Disconnect things one at a time until you get a reading of 0, that's the thing draining the battery. Fuses, alternator, relays. All this with the car off by the way.

With the truck idling check voltage at the battery terminals. Make sure you're in that 13.5-14.5 sweet spot.

I don't remember specifics on how much draw will kill a battery, but it's standard for any 12v system. Google will have some good write-ups.

 

Sorry to be stupid here: Where should I place the neg and pos contacts of the meter?

 

Most meters don't have any polarity on the 'Amps' setting, but positive (red) to the positive terminal if you have removed the positive cable, Negative (black) to the negative terminal if you've removed the negative terminal.

I would not try this with a meter that has an unfused amp probe of less than 10A.

You will always see a small draw for some things like the computer and radio memory.
Don't forget to shut the door so the interior light is not on.

 

Like Jim said, shouldn't matter. Your biggest worry is making sure you've got a fused rating. I've got a meter I bought at wally world for $7. Does it fine, but anything older, analog, or made for something specific that isn't automotive you should check.

If anything you'll just see a difference between - or + amperage. Volume is more important than the polarity here.

 

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!

 

sounds like you need to call the local NAPA or other parts store and bring your alternator in to be checked. I believe they still offer that service for free. Also sounds like something is affecting one of the fuse circuits. I recently blew one installing an after market under hood light. The light had a metal back plate that was grounding to the hood. The original was a mercury switch set up that was insulated from grounding to the hood. The new one arced when I was installing it, blew that fuse my speedometer/odometer went out, check engine came on and the overdrive off light started pulsing. I insulated the connection to the hood replaced the fuse and disconnected the battery for a minute to clear the check engine, all good now. So whatever is happening to yours is on the same circuit as all the things that went haywire while you were driving. There should be a listing of what is on which circuit in your owner's manual.

 

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!

 

Do you mean that you were reading across the battery terminals, and when you disconnected the ground cable from the battery the voltage dropped almost 2 1/2 volts?
How big was the spark when you disconnected the cable?
It's not entirely unheard of to lose a cell in the battery.

Were you able to check the voltage with the engine running, when you got the jump start? (just across the terminals, with everything connected)
14.35V would be ideal output for the alternator.
High enough to charge, but not so much as to boil the battery dry.

If you have the tester in line (between the cable and the + post) and see any reading with the ground cable disconnected something is seriously wrong.