Key off battery drain - Diesel Forum

SCMike · 09-19-2007, 08:49 PM

I have an early 99 F350 that has a 15 ma extra current draw with the key off.. I've traced it to 2 circuits in the hood compartment fuse box. #21 (Ignition switches B1 & B3) a 50a circuit has 6ma draw, and #22 (Instrument Panel Junction Box) 50a has a 9ma draw. I believe I've had this problem for around 4 mos. since my 3yr. old Optima batteries would drop 12.7 to around 12v overnight and I not sure of the timing but my alternator just went out, replaced with an "ambulance package type".. Just wondering where to look next for the most likely culprits, tried the search found nothing yet.. Any ideas, before I send it in to the electrical shop?
Thanks
Mike

On second thought maybe my 16ma key off draw is normal and my
batteries are toast.... or I'm reading my multimeter wrong, I'll
check again in the morning..
M

Tparker · 09-20-2007, 12:27 PM

According to the service manual, anything under 50 ma (.05 amps) is considered normal.

westvandude · 09-20-2007, 01:01 PM

Yup, have to agree. 16ma is pretty low. Typically this is your alarm system (if you have one) and the preset memory in your stereo deck. There must be some other load you're not measuring dropping the battery voltage.

Otherwise pull both positive terminals off when you get home. In the morning measure the voltage at each battery. If one is significantly lower than the other you have a problem in that battery and it is taking the good one with it. Could be higher internal resistance, cell problem, series connection problem, etc.

So... don't just look at the drain from the truck's circuits.

SCMike · 09-20-2007, 01:27 PM

Thanks guys, I'm just getting used to this multimeter, but after 60 minutes the draw is .15 amps on the 20a setting so I think those two circuits are the ones. The Optimas held 12.7 for 3 days after being fully charged and sitting grounds disconnected. I guess I should do a load test on each to rule out a bad cell...
Thanks
Mike

westvandude · 09-21-2007, 12:42 AM

0.15A is a little high, as was mentioned above, that's about 3 times what's normal. Sounds like the batteries are probably ok. Can always put a switch on those circuits to kill them if you don't drive it often. Kind of a pain in the neck.

shamuex2000 · 09-21-2007, 10:25 AM

I found my problem by load testing the Optimas. One failed the test. It was replaced under warranty. Then, I would have a good initial crank speed, and it would slow down fast, especially when cold outside. The cold crank performance does not last very long at all. If you get a new battery replacement, I would recommend selling it or using it in another application and get different batteries for your diesel. Shop for a battery with a higher amp-hour rating, not just CCA's. A friend's truck I work on had two fail, and my son's truck with Optimas has trouble cranking in the cold unless plugged in. This is not a good application for them.

SCMike · 09-22-2007, 12:43 AM

Thanks, But I have to stay with 2 Optimas on the passenger side, since my drivers side space now has my bypass oil filter. I live in a coastal California town so cold isn't a problem.. I need to find the shorts.. I guess I need to look at what's being powered by these circuits and check all wiring/devices on it.. or I might just get a solar trickle charger and leave it plugged in all the time...
Thanks
Mike