I have a '99 250. Replaced one battery a little over a year ago and the other one month ago. I do not drive the truck everyday but do start it at least once a week until recently. In the last month if I did not start the truck at least once a week the batteries would be dead, so now I try to start the truck every two days. The start is real slow and weak sounding. I have not had the alternator or starter checked will be doing that this weekend. I have pulled everything in the truck that would draw power while it is parked and still no luck. What else could be my problem?

 

I learned this lesson too, no matter what, you have to replace both batteries at same time. The week one will drain the new one and eventually ruin it. I did this twice before learning. Others will tell you the same thing. It's expensive but necessary.

 

When replaced the first battery I was told the other one was in good shape and did not need to be replaced. I replaced the second one on my own because of the slow starting.

 

Yes, this commonly the reason why folks only replace one. And it's probably true, the other one might have been easily within specifications. But, on these trucks, if you don't replace both batteries with new ones at the same time...you'll have problems. Unfortunately, that means that you need to replace BOTH of them now with new ones...even though the "new one" is only one year old.

It's danged expensive. When Wal-Mart was still doing two-year unconditional replacement, I was lucky enough to talk them into doing both...twice. Again, one was bad, one was good. But I simply talked to the manager and said to him, "You know that these trucks need both batteries replaced at the same time...and you don't want me coming in every six months to get warranty replacements on one, then the other, then the other, then the other..."


BTW...Mueckster told me a story this weekend that the Interstate batteries sold at Sam's Club are not warranteed the same as other Interstates, and that they aren't even made the same either. They mark it on the battery that it is a Sam's Club battery, and you can't take it anywhere but Sam's for any issues. Apparently his Interstate representative said they are NOT worth buying.

 

Make sure that ALL connections are 100% clean and solid. Even a so-so ground will cause this. And even though the connections are new on the batteries, make sure you scrape a little from the trminals to make sure there is no film on the posts. I almost replaced the batteries because of this.

 

You can easily check the alternator output with a voltmeter. Taking a Volts DC reading across the terminals of one of the batteries with the truck running should yield around 14 Volts DC (VDC), which is what the standard output of the voltage regulator should be. Due to losses in the cabling and age, anything above 13VDC should do the job. If that's good, then I would pull your batteries and have them checked at an auto parts store (which is free). As for the starter, it could be the culprit, but I would rule out the other issues first since they are more common and a free check to do.

Here's a little story about my recent battery issues:

Truck started noticeably slower but everything checked out. I was always "going to get to it" but this went on for almost 2 years. It finally got so bad that it almost wouldn't start if it sat for a day. I bought a new starter since I checked everything else and thought that a failing starter (my truck had 200K on the odometer at the time) was the only reasonable component that was bad (I didn't want to even consider the cabling). My truck finally quit on me, I pulled the batteries and had them tested and they both had completely failed. I got 2 new batteries, installed a new starter and life has been great ever since. It's been a year and the truck still starts faster than ever. Whether the starter caused my batteries to fail or if I just got a bad battery that killed the other one I will never know, but at 200K putting on new stuff never hurts.

Okay, maybe the story wasn't as little as I thought, but I hope it helps a little.

I've been there, good luck!

 

These trucks take 10.5 volts to start. If your batts are at 11.5 (one pulls the other down), when you hit the key, the GPR will pull the volts down from 11.5 to 10.5 before you even start cranking. checking your alt should be easy and it should be putting out around 14.5. Also Pull the starter off and have it checked out. I would recommend rebuilding it if it is bad instead of buying a new used/rebuild one.

Is the 'start' slow and weak if your are trying to jump it with another vehicle?

 

you do have to replace both but you don't have to get rid of them. I did mine 2 years ago. One bat was still good so I took the battery out of my F100 that needed to be replaced anyway. Still starting the F100 after 2 years.
So, if you have a need for one bat elsewhere,,,

 

I would check your alternator. it is has got to be putting out high 13's to low 14's... Check your connections to the battery as well.

If they check your battery, make sure they are disconnected from each other. Otherwise the test is worthless.

I have changed out one battery before with no issues. but definitely have each one load tested to determine if they are ok.

 

I did that at walmart and they told me they couldnt test them connected because they draw against each other. I guess I'd go elsewhere.

 

Autozone tried to test my batteries in the truck all hooked up . They tested fine that way,. Lol