Batteries going dead

[sturgeon-phish]

I have been having an issue with my batteries. If the truck sits without running for more than a week, the batteries do not have the juice to start the truck. The batteries are about 18 months old and when I had them tested in the truck they checked OK. I checked for a current draw at rest and did not have any significant current. The batteries will accept a charge without any problem from a battery charger or while running off the alternator. The ammeter reads right at 12 volts at idle and running. Any ideas? The cold only makes things worse.
Thanks ahead of time.
Jim

[Hubert]

Uhhh I think the voltmeter is suppose to read 13.8 V minus some for different temps. If you are only getting 12v sounds like a battery cell ??? may be bad. The double batteries I think can fool the avg in truck test since one can be good. You'd have to isolate them and load test them independantly.

Here is an idea for a simple at home test. Unhook batteries after a shut down and after the same parking time rehook them and if they are dead its the batteries if they crank the truck fine then the truck probably/maybe does have a short and is draining the batteries. Only thing is one bad cell will kill both batteries so if it cranks weak then one battery is dying the other is ok. No matter though they should replaced in pairs.

[prozach007]

I am having a similar problem. I have a 94 1ton 4door 2wd 4l80e I lent my truck to a friend as his truck has been in the shop for 2 weeks. Anyway I recently replaced both my batts with brand new AC Delcos. He calls me yesterday and says that the truck is dead and he is having to jump it off. After being boosted it cranked and ran just fine. He then drove it to his house, shut off for 10-15 min., then went back out, would'nt start. i went this evening to try and jump it off with no luck. I dont think I ever got enough juice to it to crank it. The glow plug light cycled once and when I tried to crank it, it turned over about twice and then everything went dead. I feel like I have a dead cell in a battery, but I am concerned bout one thing. At the back of the motor next to the fire wall in the area of the fuel filter there is somekind of solenoid that would tap when I had the key on and the truck was not getting enough power. The "solenoid" has a flat 4 plug on it similar to the pmd. Does anyone know what it is? Is this possibly my problem?