I installed my tow tune to tow boat to the beach Friday. I left programmer tuning while I went and showered after work. Came back out about 20 min later, programming was done , time to go. The truck turned over good but kinda fell off at the end before cranking like the battery was gonna die. Truck drove fine and the volts were up. We stopped one time on the way 2 min from the house to fill the boat up. Cranked fine then, cranked fine the next morning to go put boat in but would not even turn over to get boat out. Jumped it and went home about 5 min away. Cut it off and ate dinner, then it cranked fine to go get batteries checked. Test came back and said main was good, secondary to charge and test and alt had a 6v drain with everything off. So...came home...the next morning it cranked fine. Stopped by to top off boat, cut the truck off, it wouldn't crank. Jumped it, and took off cables while on the boat, and of course it cranked good. I haven't had time to look at anything but I'm hoping its just a bad battery. What y'all think?

 

I would check all of the battery terminals and the ground cable on the passenger side front of the block.

 

I'll check that in the AM, thanks

 

Whats your Alt out put on the scan gauge? and does it stay steady, also check Batteries separate with a volt meter.

 

Alt was anywhere from 10.9 to 13.5 idle with a/c and driving. Battery's were checked separate at advance auto with testing good and one good but recharge and test again.

 

If you were down to 10.9 after the gpm shut down then you more than likely have a faiing alternator providing all of your connections and grounds are good. If that 6 volt drain on the alt. was with the truck turned off then a diode is probably failing. Usually a drain is measured in amps.

 

Those short trips are killer on the alternator and batteries too.

If the engine has only been running a minute of two and you're making a short stop; leave it running.

Josh

 

It hit a 10.9 once on scan gauge but mostly stayed around 12.3 and up idle.

The drain was with engine off and doors open, so nothing was on except door and interior lights.

Advance guy said volts

 

I normally do leaving it running but just forgot when I parked. Plus it cranked fine that morning I figured it was a fluke. I'm about to leave for a 2 hour drive home. I'll watch the volts and FICM volts on the way home.

 

I see that you have a 280 amp alt how old and what make? also how old are the batteries? you mentioned having to charge one that could have killed a cell before you charged, Paracitic discharge, sorry for the spelling I just woke up,or there's the glove box lite, brake controller ,Aux cell charger, OBDII via scan gauge. Thats pulling power.

 

I got alt in April and its a tenney alt. the batteries aren't that old. But I did think about things on the way back from the beach. My brake controller made my f150 go dead so I unplugged it. I'll try scan gauge if it goes dead again. I did go back by an Advance auto and they checked batteries again. The batteries checked fine at 12.4 and 12.9

 

Do you only have the problem when boat trailer is hooked up? If so it might be your trailer wiring causing the draw..????

 

Don't think so, I've gone to the lake twice and no issues.

I'm going to go by a local company tomorrow that rebuilds bigger stronger alts, I'll see if that is where the problem is. I was told when I got this one that I didn't need to add bigger wires...so we will see v

 

The batterys should be closer than that. I'd be suspect of the 12.4 battery. You need to do a hydrometer test on the batterys.

 

What kind of shops can do a test like that?