my battery keeps dying on me when i let my truck sit for a few days. it holds a charge fine for a day as long as I start it up once in a while. i do have under drive pulleys. think my battery is junk?

 

yep, otherwise your alternator isn't charging the battery. Does your volt guage move to the right when you accelerate?

 

Test it with a volt meter or have it tested if you are not sure,this will rule out the altenator, but if the battery is over 4 years old just replace it and be done with it.

 

most likely the battery. happened to me. mine got a lot worse. it would hold a charge for maybe 5 minutes. really sucks when you have to push a 4000 lb+ truck to get her started again.

 

First, with the truck not running, test the battery with a voltmeter to see how many volts the battery has. Then check it with the voltmeter with the truck running to see how many volts the alternator is putting out. It should be higher with the truck running. If not, then the problem is most likely the alternator, not the battery. Any place that sells batteries can do this test free of charge.

Mike

 

Probably is the battery, however... I just had a similar problem with my son's Cougar. The battery would go completely dead overnight. But, if I charged it with a battery charger, it would start the engine just fine. I measured the voltages as described above. After I had charged the battery it would read about 12.5V or so with the engine off and about 14V with the engine on. Sounds right, except the battery would still be dead in a few hours. I was gone for the weekend, so the wife went to the store and bought a new battery. Next morning, it was dead. So, I decided to test a little further, and check the current draw through the battery with the key off. I was shocked when I got a reading of between 30 and 60 amps with nothing turned on. I unplugged every fuse one by one but still had the big current draw. I finally unplugged the lead going to the alternator and, viola!, current went to zero. So, after a quick trip to NAPA verified the alternator had a short, we were back in business.

So what I'm saying is don't just assume it's the battery and buy a new one. Just about every auto parts store will test batteries and alternators for free (at least the ones around here). So if it's at all possible, take BOTH in to be tested.

 

Yeah could be battery, alternator or some other circuit drawing current while off.

A good condition battery should read maybe 13v whith the engine off. While the engine is on it should be 14v up to maybe 18v. If the battery is 4 years old, it may be getting to the end of its life.

You might also check to see if the battery terminals are clean. use one of those battery terminal brushes to clean things up. Also make a mix of Baking soda and water and use a rag to clean up the top and sides of the battery. DO NOT get any inside the battery. If it foams and sizzles a lot, you have battery deposits on the outside of the battery and may have a sneak circuit drawing current that way. The baking soda will neutralize and clean off that deposit.

A good shop will usually check your alternator and battery for free.

If both battery and alternator are good then you have some circuit drawing current. Maybe a stuck door light, glove box, etc. You will need to pull fuses and use a current meter to track it down. A pain but will usually pin point the problem.

Good Luck,

Jim Henderson

 

i beleive when i bought it a few months ago the guy said it was a new battery. when I accelerate the voltmeter does go up. i bet it is a circuit drawing off current. how do i test for this again?

 

With the ignition off, and no lights or other accessories on, remove the negative battery cable. Take a multi-meter (you can get one at any auto parts store or Sears), set it to AMPs. Attach the black (negative) lead to the battery's negative battery post, attach the red (positive) lead to the negative battery cable that you removed.

If you see a draw of AMPs, then you have something in the truck that is shorting or drawing power. The first thing to test is the alternator. Remove the electrical plug from the back of the alternator and see if the current drops. If it does, then the alternator is internally shorting (two have already failed in my '92 truck, so this is common). If the current doesn't drop, then remove each fuse in turn to see which circuit is causing the short, then trace the wiring down until you find the short. Shorts are uncommon unless you've fooled with the wiring somehow, like wiring in a trailer harness.

My wonderful :-( Ford dealer told me that my truck needed a new battery (when I was lazy enough to bring it in for this problem), and charged me $145 for a new Motorcraft plus installation. The next day, the truck was dead. I did this simple test, and put in a new alternator. Probably would have needed a battery sooner or later anyway (at least thinking so makes me feel like less of a fool). But don't always assume the battery is bad. These trucks have huge heavy duty batteries and will go many, many years without failing.

 

Just remember when you are doing the AMP test, that having the door open to get to the fuses will turn on the interior lights, thus drawing current. The job is a lot easier if you have an extra set of hands to pull the fuses while you watch the meter.