Starting and charging problems

[kzman77]

Hey hope everyone is having a good Sunday. Here is my problem:
A week ago my excursion was having an issue starting. It progressed to needing a Jump. So I took it to autozone and had it tested. They said one of the two batteries needed to be replaced. So I did that and they tested the alt and their tester said the alt passed the test. First few starts were strong then then they became progressively weaker. I metered the alt output both times when it did start and it metered between 12.6 and 12.9 volts at idle. Isn't that a little too low to charge a two battery setup? Is there anything else I am overlooking? Thanks again.

[strokin95style]

check the battery cable terminals, if they are the slightest bit loose, it will make a big difference. Having similar issues with mine, waiting on the dealer to get my new battery cable in since its 15 years old

[kzman77]

So loose or worn battery terminals would affect the output voltage on the alt? Also where can I get a new + battery cable since it's the linked cable for 2 batteries?

[jbeasts10]

Alt. output should be around 14 volts.

[strokin95style]

wont affect alternator voltage, but will make a difference. I tried for 30 minutes tryin to jump start my truck this morning at 5:30 when it was like 35 degrees out and never got it started...even with starting fluid. i kept messing with the hot cable and found one that was barely loose and i squeezed a vise grip on it as tight as i could and when i turned the key it fired right up. if you dont have a good connection on both batteries and a good ground, the engine will not crank fast enough to fire. I picked up a new positive cable yesterday (saturday) from the local dealership for $75 with my discount. im not sure what they list for though. it took me about 30 minutes and i had it on. no more slow cranking, the engine spins over like its a brand new truck now. Im not saying that you need a new hot cable, but make sure all your connections are clean. the factory cable end on the pass side battery is known for breaking where both cables run into one connector. take 10 minutes and clean all 4 battery posts and see if that makes a difference on the starting issue. Good luck.

[icysmooth]

This may sound dumb-but can you test alt. output with another meter?
If it passed at parts store-chances are the meter you are using may not be reading right-I see this all the time-depending on the quality of the meter,if you use another meter and reads the same then it's probably bad connections or overheated wiring
Not many people know this-but when copper/other bi-metals are cold-it's a conductor-but when over heated-it becomes a resistor (heat) very quickly,and won't let enough current pass through when hot.
Just some food for thought