Engine/Transmission (1994 - 1998) how to tell when/which battery is going bad or is bad?

[raxley]

My 1994 2500 has been hesitating to start the last few days. It just doesn't feel like the starter has the 'guts', it feels weaker. Should each battery have a certain voltage if they are charged? Isn't it something like 13.2 volts?
Of course I'll check my cables, although I cleaned them well and put the anti corrosion stuff on there about 6 months ago. I understand you should change both batteries if one is bad-does it hasten the other battery's demise if you don't change both?
Thanks for any info!

 

[Mingoglia]

I've never seen a situation in 14 years of dual battery ownership (in AZ, where we blow through batteries), where one battery is good and the other is bad. Once one starts going, the other starts compensating and by the time you notice it's no good either.

A fully charged lead acid battery should be at 12.7 volts when fully charged. So I'd put it on a battery charger to insure it's fully charged. Then take it off, let it sit overnight, then test it again. It should be roughly the same voltage. If it drops under ~12.5, your battery(s) are starting to go out. It shouldn't drop more than a tenth or two overnight.

 

[Missouri Mule]

Have them load tested. Batteries voltage readings should be the same.

 

[BarryG]

Another possibility if the batteries check out fine could be the batteries are fine and the starter contacts or brushes are going. They have been a somewhat common issue at least the contacts. There are kits out there to replace them like from Larry B who has everything you need from individual parts to a variety of rebuild kits to new denso starters
http://www.fostertruck.com/dodge/starters.html

 

[Mingoglia]

Another possibility if the batteries check out fine could be the batteries are fine and the starter contacts or brushes are going. They have been a somewhat common issue at least the contacts. There are kits out there to replace them like from Larry B who has everything you need from individual parts to a variety of rebuild kits to new denso starters
http://www.fostertruck.com/dodge/starters.html

Good point. I had this exact thing happen, and bought the kit from Larry B. My truck started "sounding" like the batteries were going due to the slow start due to the starter contacts. The kit was cheap (I think in the $30 range?), and once installed my engine practically jumped out of the engine compartment it was starting so fast....on the same batteries.

 

[raxley]

It just barely started this morning. It seems to hesitate before turning over, then it spins ok. I checked both batteries, separately, and they both have 13.1 volts. When I start it, at idle, my VOM shows 13.8 V. I'm going to run down to O'Reilly (used to be Kragen's) and have them check the charging system, but it seems to be OK, I think 13.8 V will charge the battery. I also replaced those small brushes in the alternator a year or so ago.

It sounds like I'll be getting the starter contacts and the brushes. For the contacts, and another solenoid plunger they are $25, the kit with contacts, brushes, plunger, brush holder plate with new springs, and a 10 mm wrench, it's $65. There is a complete rebuild kit for $110, it has all of the above and bearings for starter and new clutch/pinion drive.
Thanks everybody for the advice. Now I can work around this, and I know what to do. Great advice!
Wow, a new starter is between $450-$560!

 

[B.G. Smith]

The hesitation sounds like a bad battery. Did you disconnect the cable from one when you checked the voltage? bg

 

[Tuesdak]

I've never seen a situation in 14 years of dual battery ownership (in AZ, where we blow through batteries), where one battery is good and the other is bad. Once one starts going, the other starts compensating and by the time you notice it's no good either.

A fully charged lead acid battery should be at 12.7 volts when fully charged. So I'd put it on a battery charger to insure it's fully charged. Then take it off, let it sit overnight, then test it again. It should be roughly the same voltage. If it drops under ~12.5, your battery(s) are starting to go out. It shouldn't drop more than a tenth or two overnight.

I have seen them be bad separately, but, you replace them in pairs no matter what. Even under warranty you buy the second battery if you have to... The low voltage from old batteries or a shorted cell takes out both as the other good one can't charge fully. A sudden failure like boiling dry, cracks leaking out, cracked plates, or burning a internal connector open leave you with one good and one dead battery. You always replace both anyway as the older battery will drag the new one down to it's level.

Testing dual batteries requires you to disconnect the batteries from each other. A wimpy clip on tester isn't going to drag both batteries down like your starter does. (All you have to do is disconnect the negative cable on one battery to test. Never just disconnect positive cables!) The tester sees one good battery and the other one is open or dried up = pass. Disconnect them from each other and the bad battery is clear.

Remember to disconnect the grounds (negative) on both batteries first then work on the red positive cables. You drop a ground cable - who cares as nothing happens. After the grounds are disconnected from both batteries dropping a positive cable won't matter.

Test batteries separately first. Clean and check grounds and cable condition. Check positive cables and connection to the starter. Check voltage at starter battery terminal for major drop when cranking, Then suspect starter.

 

[Gary - K7GLD]

Lots of places for significant voltage drop besides the batteries themselves - internal (unseen) corrosion in BOTH ends of the battery cables, both hot and ground cables. Poor grounding between engine, truck frame, and batteries. Poor or corroded starter connectors. And, good voltage at the batteries under NO load, can drop like a rock under load...

Just relying on checking voltage directly at the batteries can be very misleading...

 

[JMcCoy]

I have seen them be bad separately, but, you replace them in pairs no matter what. Even under warranty you buy the second battery if you have to... The low voltage from old batteries or a shorted cell takes out both as the other good one can't charge fully. A sudden failure like boiling dry, cracks leaking out, cracked plates, or burning a internal connector open leave you with one good and one dead battery. You always replace both anyway as the older battery will drag the new one down to it's level.

Testing dual batteries requires you to disconnect the batteries from each other. A wimpy clip on tester isn't going to drag both batteries down like your starter does. (All you have to do is disconnect the negative cable on one battery to test. Never just disconnect positive cables!) The tester sees one good battery and the other one is open or dried up = pass. Disconnect them from each other and the bad battery is clear.

Remember to disconnect the grounds (negative) on both batteries first then work on the red positive cables. You drop a ground cable - who cares as nothing happens. After the grounds are disconnected from both batteries dropping a positive cable won't matter.

Test batteries separately first. Clean and check grounds and cable condition. Check positive cables and connection to the starter. Check voltage at starter battery terminal for major drop when cranking, Then suspect starter.

This is all solid advise. Though it is not suggested, I have replaced one battery at a time before with success. I have rebuild many starters. You will likely not need bearings for your starter. Save your money. I would just get the contacts/brushes and plunger, and call it the day. Good luck

 

[Denis]

Every once in a while; say every 6 months or so; I disconnect 1 battery a see if the other will start the engine and then do the other battery by itself. This ia a good way to make sure each battery is good. My experience is when 1 battery is weak the other is not far behind.

 

[gcorron]

I've been using a single Red top Optima for years. Makes trouble shooting much simpler. :-laf Our generators had 4 8D batteries and we checked them monthly with load testers and for specific gravity.

The Larry B contacts also help, did that long ago as well. At 18 years, it COULD be time to rebuild the alternator as a preventive measure.

When I started using the Optima, I saved a few bucks, but now days, it would cost me less just to use the 2 batteries, go figure.

George