95 TopKick battery drain problem

[bstrom1953]

This truck just had a new alternator installed and replaced the 8 year old batteries. The alternator charges properly.

Because we previously had times when the charged batteries would go dead overnight, I checked the current to ground with the key off. The ammeter immediately read 28 ma. About 20 seconds later it dropped to 18 ma. and then finally settled at around 8 ma. Is this normal? Shouldn't the current drain be zero when the key is off? Is the computer on all the time and draws that amount?

I pulled fuses at the fuse block mounted on the firewall and found two 40 amp circuits where the current was going...around 4 ma each. FYI it has a Cat diesel engine. I'm just wondering how long two big 12 volt batteries will hold a charge with 8 mils of current going to ground.

Thanks for any ideas.

[DeltaP]

8ma is about what the ecm will draw. That shouldn't make a dent on a pair of fully charged group 31 batts in parallel. What other accy's on the truck? Lift gate, refrigeration unit? Lift gate only being used while truck is running?

[brcidd]

Rule of thumb is anything less than 50 ma draw is fine.

[DeltaP]

That's some driveway you got there.