The age old question- Is it the battery or alternator ?
I was towing my boat to the lake yesterday when I noticed my stereo cutting out, I looked at the volt gauge and noticed it was very low, however the truck kept running. Initially I presumed I had broken the belt but about 30 minutes down the road the volts popped up to normal and the radio worked again. After having mechanical issues on the water with the boat I got back to the truck and it started up and ran fine all the way home.
I just put the voltmeter on it and everything once again seems fine. The battery when not running showed about 12.3 volts, When running it was at 14.2. I turned on every accessory and didnt notice any change in voltage. The volts did increase when I revved it up. Should I suspect that my alternator is going out ? Or am I missing some thing ? Thanks for any input !

 

That's a crap shoot. Unfortunately, you are probably going to have to wait until it fails completely to figure out which one is culprit.

 

Did you happen to notice if your voltage was slowly decreasing or was there a sudden drop ? If the alternator stops charging the battery gets slowly depleted, if there's an issue with the wiring it will be an immediate change.

 

Good question DerTruck. I did not. I presume it happened quick because when the volts came back up I noticed it happened quickly. I havent had any electrical problems with this rig in the 7 years Ive owned it. Thanks for helping, and thanks again to HeyYou for replying every time that I post here ! I appreciate the help. Now I just gotta figure out what is goin on with the boat engine !

 

So it happened yesterday. I was coming home from the lake towing the boat. I noticed that the volts were no longer registering on the gauge, she kept going for a while, but I had lost turn signals and all other accessory power. Then it basically just started to stall, at first it just felt like I was getting a flat, but after I came to a stop on the shoulder I realized it just died. Fortunately I have a spare battery in my boat. I was able to swap it out for the dead one on the shoulder quickly. The beast fired right back up and managed to get me home thankfully. However I noticed that after I swapped the batteries, the replacement one was only showing around 11 volts on the gauge, however it didnt drop at all during the rest of the drive home. This would make me think the problem is probably the battery. The problem I now have is that the battery that was in there doesnt have a single spec or model # on it ! I looked in the haynes manual but it doesnt list a specific battery rating anywhere !

 

I believe a 34-78 is the proper size or the truck. That's the one with side posts and top posts too.

I chose to get one that was a little higher cranking amps and I can get the number for you later after work. But if you call any parts store they will be able to give you a couple options.

 

Thanks man

 

Just get the biggest you can fit there.

 

Looks like I have an EPBUL 34-78 battery. It doesn't totally fill the battery tray but it's the biggest that would fit between the posts for the battery holder.

​​​​​​I can't find the exact factory specs but I believe they came with a 600CCA battery and the one I put in it is an 800CCA. Where I live it can easily drop down to -40° so I went with the bigger one. I also find my truck starts like a dream too but that could be unrelated.

 

Im not certain, but at this point I suspect the problem is the alternator not the battery, but it could be both . I went to the auto store asking about this, on the way there the volts started as normal, then dropped to around 11, then came back up to normal again by the time I got to the store ! The clerk re checked my battery and noticed that NOT running it was reading 14. Then when I started it the volts only tested around 12, at both the battery and the alternator. The store owner said it could also be the voltage regulator which is apparently in the computer, and requires replacing the entire computer ! The clerk however convinced me that he didnt think that was the case, siting that if it was the regulator it would just drop and not come back up.. . Im not sure at the moment, but I went with the clerks assessment and bought the new alternator, I left the battery at the shop for them to charge and test.. Im hoping to swap out the alternator this evening.