Hi all.

my truck didn't have enough power to crank this morning. New batteries too.

I'm about to do a parasitic draw test but never done it on a dual battery. I don't think it matters but do I need to disconnect one of the batteries?

since the fuse box is in the cab how do you "close" the door too keep the amps down from the door light?

does thebhood Lach need to be closed?

any other tips?

08 f350 6.4

 

I think you can take a screwqdiver and with drivers door open trip the latch to negate dome lights.

Be careful on returning to normal though.

Maybe try hard key first upon returning door latch to normal?

 

Are you sure your charging system is OK? What is your voltage before starting the engine and what is your voltage at idle?

 

I'm getting 12.8 on the batteries and 13.96 at idle

 

Batteries with a bad cell can still have a good reading at rest, you have to put a load on them. Turn on your headlights and check the voltage again.

Denny

 

Last time I installed new batteries (a couple of years ago), I tried to get cute with providing "ultimate" corrosion protection, and somehow allowed the silicone dielectric grease I covered the top of the battery terminals with to get inbetween the truck battery terminal and the battery post terminal.

Everything worked swimmingly for the first year, but by the end of the second year, I felt that something wasn't quite right, and I knew it wasn't the batteries (rather expensive TPPL AGM's which have lasted as long as 10 years) and it wasn't the alternators (dual, and high amp).

It actually took something else to go wrong (truck wouldn't start at all, due to alarm not receiving power, as a result of a wire crimp failure by the alarm installer) that forced me to investigate all of the vehicle wiring from dash to batteries. That was when I noticed how "loose" the Ford terminal (older style lead block, different than your stamped terminal) could "slip" around the positive battery post, lubricated by the silicone dielectric grease.

I'm generally pretty careful when it comes to installs. However, adding the silicone dielectric grease over the tops of the terminals was literally "over the top" and unnecessary given that the batteries I have are recombinant, having no liquid inside, and no outgassing outside.

So the "tip" here is... be CERTAIN of the film free cleanliness and tightness of the battery terminal connections.

I experienced a huge difference in starting responsiveness, with no change in batteries, starter, or alternator... simply by tidying up and tightening up wiring.

In my case, I removed the battery terminal bolt, and replaced it with a stud I made from cutting off the head to a longer HDG carriage bolt and chasing the threads with a die, and using solid brass nuts with copper washers on either end of the stud to fasten all the heavy cables to the battery terminal with. Your case will be different, as you have a different style of OEM battery terminal, but the point remains the same... there is value in revisiting battery terminal fit up, especially after a new battery install.