Let me start this by saying that I don't have any electrical testing equipment or meters. I will take the truck to Autozone or Advance Auto Parts after Christmas to see if they can test them for me. Before I go, I would like to know what everyone thinks is the likely culprit, if possible.

This has started fairly recently. I noticed that the needle on the battery gauge would drop down to between the "r" and "m" in normal when the truck is in gear(automatic) and stopped at a light. The needle will also move slightly back and forth. While driving, or when in park, the needle is between the "m" and the "a" in normal and does not move at all.

I recently replaced the belt tensioner because the pulley wheel broke off. The belt is a new Gatorback and is at the correct tension.

Do you think this is a problem with the alternator not charging properly or could it be the battery dying and not accepting a charge properly?

Thanks, in advance, for your suggestions.

 

With the truck running pull the positive battery cable off of the battery. If it stays running then the alternator is good.

 

Thanks, I will give that a try this weekend.

 

you can take it to a auto parts store and they will check your charging system. or just use a cheap volt meter. with the engine running and lights on oyu should still be getting above 12 volt. there are people that will tell you that disconnecting the battery when the engine is running will mes something up, on the older cars it works fine, done know about newer cars or trucks with computers, i have a couple volt meters so thats the way i check it, but i also have a old 70 mustang and have checked it by disconnecting the battery.

 

I do not have a meter, but if I was to get one, how do I test the battery and/or the alternator? Thanks!

 

Pulling the battery terminal while the truck is running is an excellent way to fry the alternator, don't do it. The battery will have about 12.6 volts with the truck off and about 14.6 running if the alternator is good. Yours sounds like a possible voltage regulator problem, which is part of the alternator but can be replaced separately.

 

My truck has this same problem. When I back in my trailer at night there is a noticeable difference in the brightness of the trailer lights when I accelerate vs. idling. When I get on the gas they get brighter. My gauge does the same thing as described on this thread. But I have never really looked into it.

 

Something I forgot to post was that my dash lights get dimmer when sitting in gear at idle. Another member has suggested that dim lights at idle could mean the battery is getting weak. I am going to get the battery tested, hopefully I will have an answer this weekend.

 

It absolutely will not. What do you think the alternator does? It keeps the battery charged. While your truck is running the alt powers everything. Your battery is just a reserve. It's sole purpose is for starting and powering accesories when the engine is off, or when the alt. dies.

 

I just got back from Advance Auto Parts where they ran a systems check on my truck. The results are as follows:

battery: 12.36v, good, but low on charge
starter: cranking normal 10.41v, 283.5a
charging system: no problems, charging system output test is normal

the guy at the store said the voltage was low to the starter and I should look at the connection from the battery to the starter for problems.

Based on above information, any new suggestions?

Thanks!