I've read through the archives as best I can today but don't see anything real specific on this, so I'm sorry if this has been visited before;
I suddenly came out to low batteries a couple of weeks ago on my 99 7.3L PSD. I'm super busy with work so just switched to my second truck and lety it sit a week or so. I put the charger on the batteries, one of which was in the truck when I bought it, 5 years ago and the other I bought less than 3 years ago. I have tested the electrolyte in the batteries and both test good, they also both hold a charge BUT I noticed the voltage dropped (on the newer batt, oddly enough, right side looking in) to 7.- something when I cranked it. Are the tests misleading me? Do I simply need new batteries (or one, at least)? Or, could this be a starter problem, or both? I read earlier that a new starter spun super fast compared to the old one when someone had replaced it with cranking problems.....is this the likely culprit?

If this is the case, can these starters be rebuilt and work well? I now live on an island in the Caribbean and of course brought my PSD down with me. Problem is, parts are not easy to come by and expensive to ship. If a rebuild is not a great idea I will just bite the bullitt and ship, so please give all advise available, including where to buy from in the US.

Thanks in advance for any help.

btw, due to prior experience my first thought on this after I charged the batteries was cps, as I brought two down with me and had replaced two in the past, but s/thing makes me think I'm just not turning the motor quick enough now.

Cheers, David.

 

If you are testing both of them at the same time, then yes the test is misleading. Both batteries will need to be disconnected and load tested individually.

Also, it's best to replace both batteries at the same time.

 

Yes, I tested both while disconnected also and they both showed 12+ volts but not sure this is a good indicator of condition. Any recommendations on battery types for this truck? I used a Duralast 935C/A last time but don't remember why. With no good info available down here, is that in the range of what I need?

Thanks, D.

 

Like Curtis said, these batteries act as one big battery, not two seperate batteries. If you only replaced one, the you only replaced 1/2 of your battery and the older, weaker one has pulled the other down. Also, your batteries are only as good as your alternator. Make sure it is doing it's job.

 

I think 750 is the minimum requirement for the batteries. As Curtis said, replace both at the same time. I'd also stick a meter on your alternator when the truck is running and see what kind of voltage it's putting out. If you're putting out less than 14 volts, the alternator may be on it's way out.

 

Nah, you need to load test them. An auto parts store can do that for you.

As for batteries, its up to you. I have some cheap Energizer batteries in my truck that I bought from Sam's Club, and I've had them for 2 years now. 900 CCA's, and the truck fires right up in below zero temps.

 

Thanks Curtis, but no auto parts stores here, I'm on a relatively small island. I agree though, I think the 7volt reading under cranking might indicate weakness, plus the age of course. Thanks Barry and Chris, I had intended to test the alternator also, been standing there with my meter but not much use as I can't get it started.
The thing that got me thinking cps yesterday was it seemed to turn over pretty quickly after the first night on charge but still didn't fire up. Before that, I did wonder about an alternator problem as that could have been the initiator of the whole dead battery issue.
I guess I have to eliminate them all one at a time. New batteries first, then if no start, maybe cps replace, then check the alternator output. Am I missing anything?

Again, thanks for all y'all's help.
David.

 

7 Volts cranking is not enough you need 10.5 volts minimum. You have to replace both batteries. The batteries are wired in parallel, so the power will equalize. The weaker battery will pull the stronger one down, as Barry said.
With new batteries and the truck runnung you should have 14 volts or so. Also check all connections including the grounds, especially where you live in a "salty" enviorment. the salt air will corrode the wiring much more quickly.

 

I guess we have forgot our manners in our effort to help you, but welcome to the site. I'm sure we will get you back up and running.

 

You are right Barry. David I apologize Welcome to FTE!!!!

 

Welcome David to

Good point Jim. Ground connections are to often overlooked. They are every bit as important as the battery connections. What good is battery without ground, and vice versa.

 

Thanks Robin. The grounds are essential to any electrical system. The ground on a dc system provides a "return path for unused electrons" You have to have a complete path in order for electricity to work.

 

Thanks for the welcome and for the advice guys and sorry for the delay responding.
Everything takes time to get here but I managed to get two new batteries that would fit under the hood on Saturday...truck cranked and started right away! BUT, after driving only a few miles, I noticed the battery light on again so aborted my trip yesterday and came right home. I put the charger on the new batteries and am guessing (and hoping) I should be able to start it, not run any electrical items and get it to where I can have the alternator checked...is this a likely sounding solution to you guys?
I loaned my meter out and my other truck is at the mechanics anyway so figgered that'd be the first logical step. Is there anything else I should be checking???

Again, thanks mucho, David.

 

Sounds like an alternator to me mine acted the same way sure nuff alternator was shot. Welcome to FTE btw

 

I agree, had the same thing happened on a trip to Colorado last summer. Found a parts store that was open on a Sunday afternoon and just happened to have the right one. Replaced it in there parking lot and we were on the way. Man was I lucky.