Current draw question

[AZFiveOh]

Recently my 02 F250 starting getting very hard to start. I've got 2 optima yellow tops in it and after a night of sitting it's slow to start and after 4-5 days it needs a jump. I did a current draw test and found something was pulling 3A with the key off. I started pulling fuses and when I removed #19 (Body security module / 4X4 module) the current draw dropped to only a few milliamps. Interestingly enough, if I put fuse #19 back in and pull fuse #35 (Instrument cluster) the current draw goes away as well. So, if I pull either fuse, the current draw goes away.

Has anybody else had his problem? The fuses never blow so I know nothing is shorting. I'm pretty sure I've got a bad part somewhere I just don't know what part.

Thanks, in advance, for any ideas or assistance.

[NoRalPh]

If you monitor the trucks draw, it takes some time for stuff to shut down long after you turn the key & shut the door but, 3Amps IS a lot!

Sounds like you've narrowed it down some though

If it was me, I'd pull #35 and see if you had a problem after it sits again (#19 is gonna always have some draw)

Also, how are you recharging those yellow tops after they die? Optima's don't like to be charged at too high a rate.... You can damage them by doing so.

[AZFiveOh]

Thanks for the reply. I never let them fully discharge. If they do get low enough to where the truck wont start I use a step charger to get the batteries back to par.

The 3A draw is far from normal. I let the truck sit for about 30 minutes before I started testing for the draw. What I find puzzling is that I can pull fuse 19 or 35 and the current draw disappears. It does not matter in what order I pull them or the draw is even further reduced if I pull them both, the current draw of 3A disappears if either fuse is pulled. It's not like one is drawing more current than the other either. The current draw is down to about 80mA when either 19 or 35 is pulled. I can't even tell how the two circuits are related.

[dfdinc]

It sounds like you are dealing with a relay problem with one of the circuits feeding power through a relay to run the idem. And the other circuit feeding power to the switch leg of the relay. I would try to find out what items are fed from the circuits involved and then try to find the location of relay for those items. If this is the right cause of the draw the relay should be good, because when you removed the power from the switch leg you didn’t have any draw anymore so you will then have to trace from that relay to find what is energizing or grounding it. I hope this helps and sorry for the late reply.