Altenator Going??????? Please Help

If it's putting out 13.7-14.1V then your alternator is good. It's possible to get a bad battery but why did you buy batteries in the first place? You probably have a small parasite drain somewhere.

I'm not sure what you mean by that? Do you mean low voltage alarm? You have to jump the truck off? If you are watching TV or using accessories won't last much more than 8 hours depending on what you are doing.

 

It may well be the starter. What you describe points to it. With a Volvo like yours, when the voltage drops, you start to lose accessories in the tractor, such as dome lights, c.b. power, etc. in order to preserve power. If all that is good, I suggest a starter test.

 

As Condo said, your alternator charging voltage is normal. I also have the same confusion & questions of your statements, that he mentioned.
In the future, if the batteries are found dead, first try to determine why. Did you leave any powered items on? Also, first try disconnecting and charging them, followed by a short rest period and a load test on them. It's possible a simple recharging can eliminate having to replace all of them.

Also, anytime you replace batteries, always promptly test charging voltage to make sure that it's normal and doesn't drain new batteries.
Engine off/Key on is battery voltage only, which should at close to 12.5 as you indicated. The .1 rate drop is normal, as you are slightly draining the batteries by having the key on (ECM and other "electricals" are being powered).

Not sure what you man exactly, for either statement.
What do you mean by "rough starting"? Is cranking speed lower than normal? Or does it crank fast enough, but doesn't want to readily start?

Edit: I didn't see your last post prior to typing mine. You might want to check amperage draw on that fridge. It may be higher than it should be.
Is it a 12 volt fridge, or is it 110 v and running off an inverter?

 

you are expecting too much, thats ALL, when you want to use fridge and such things, only when truck is running

 

O.k., I have another idea. Our 07 Volvo 780 was having electrical problems with low voltage, and one of the things the dealer found was the metal strip that runs between the batteries was really corroded, and we replaced it. It could be as simple as that. I'd also check to make sure all of the battery terminals are in good shape. You may only be getting part of the power available from the batteries due to bad connections. It would only take one bad terminal to effect the power.
Also, if the fridge is the stock Volvo fridge, it won't run if the voltage is too low. I've left mine on for days with no effect on the battery power.

 

If nothing is draining your batteries (lights on, etc), and all wiring and connections are clean and tight, including the frame ground, then the problem could be a leaking diode in the alternator. If you start with fully charged batteries, it will show normal charging voltage. But if the truck sits overnight, the leaking diode will drain the batteries.

 

Very true. The OP should always check for current drain with engine off/key off (and fridge/all accessories off), to eliminate this possibility.