Ok... I'm a newbie to this forum but have already found it invaluable. My first issue was addressed very quickly for which I am most grateful. I have another as a follow-up:

I have a dual-battery setup on my 99 F250 7.3L PS (101k miles). I had to boost it yesterday (passenger side) to get it started and it still doesn't seem to be holding a charge.

Do I have to pull them both out and get them tested to find the bad one or should I go just go ahead and replace both? Is there something else I should check that is unique to a dual-battery setup before I go this route?

Also, Chilton or Haynes - which one is best?

Thanks!

 

I would probably just go ahead and replace both to be on the safe side, but I'd also be sure to check other components to make sure they aren't causing the batteries to fail (alternators, cable shorts, etc.)

As far as the manuals, I've always had better luck with Haynes manuals. As far as I know Haynes is the only one that has released a manual for the 99-02 Super Duty's\Excursions.

Hope this helps.

basstardo

2002 F-250 Lariat, 7.3L PSD, 6 Spd Manual, 4x4 Off Road Package, Line-X Liner, grille gaurd, soft tonneau, altezza tail lights (adds at least 15HP ), more to come...

 

i would have them checked and just change the bad one. no need spending the money to replace a good battery

 

tr8727

First test BOTH batterys, if one is bad, replace BOTH of them. If you don't you will weaken the new one and shorten the life if the new one.

If the batterys test ok then check all the connections and the charcing circuit.

Hope this helps, and BTW welcome to the site.

Jim

 

I had this same issue a month ago with my '99 PSD. Had Motocraft batteries with the little "window" that shows you green for good, red for bad, etc. One battery was showing red-I replaced it. Other battery was showing green, so left it alone. Well, the problem got worse-so started wondering about alternator and all that. Someone out here said the weaker battery would pull juice from the stronger battery, and essentially make the entire system weaker - I tested that with a voltmeter and sure enough, the battery I didn't replace was sucking the new one down to a level where although it would turn over, it wasn't gonna start. Replaced the other battery a couple days later, and haven't had a problem since. Two batteries-approx. $120. One alternator-approx. $260+ with core.

 

Be aware that the alternators on the PSD have been a higher failure item.

You can check the proper operation of you alternator if you've got a digital voltmeter. Both batteries are wired in parallel so it doesn't matter at all which one you jump start, charge or get voltage readings from.

From a cold start, there is a time delay before the alternator puts out full voltage- I think this is to protect the glow plugs. When you first start the truck, you should read around 12.5 volts across the battery terminals for the first minute or two. That's the "low" charge setting. After a minute or two the voltage should quickly jump up to a minimum of 14.0, depending on how cold it is, it will run around 14.25 after the two minute delay.

The PSDs are unusual in having this two-step charging sequence.

You can read the voltage at the "power pickoff" or cig lighter socket, too.

Start the truck and watch the voltge. It should initially start around 12.5. Then you should see it rise to at least 14.0, preferrably 14.25 or a little more within about 2 minutes. If it *does*, and your batteries are still weak, your batteries are shot- They're not taking a charge from the alternator. Have them load tested if you can and plan to replace them. If the voltage does *not* rise up to at least 14.0, the problem is most likely your alternator or charging circuitry.

Good luck.

 

While waiting for the truck to warm up, I have several times noticed that the lights (interior & exterior) get brighter as though a small surge. This makes perfect sense according to your 2-stage charging explanation.