OK, I brushed clean the area under the fuse, sprayed it with contact cleaner. Sprayed the fuse socket too. Then I snapped it all together with some trepidation, but it seems ok. The truck runs without issue. Phew! More testing this afternoon. I'm happy to report that I am seeing better results. Inserting fuse #21 no longer makes a change in the load going to the fuse distribution box. Now I am seeing the load gradually drop down to around 70-80 milliamps. That still seems high, but better.

What is the proper load on the battery for basic systems (clock, etc.) when the vehicle has been off for an extended period?

FWIW, I searched on my macro problem - dead battery when the vehicle sits for a week and found a large body of complaints by Ford owners. This was not just F150 owners but also many other newer Ford products.

 

I found it varies with trim options. Like a base model won't draw as much as a fully loaded premium model.

In any event, I have battery tenders and equalizers on all my vehicles. So if I know I'm not going to be using a vehicle, I keep it on the tender, just like I do my motorcycle.

It's not good for a battery to be run down and discharged. Especially lead acids. SLA and AGM is a little different. They are more of a deep cycle. But you should still keep them somewhat charged and used.

 

This is a stock 4WD XLT package. I am using a battery tender right now but that doesn't do me any good on an extended camping trip or when leaving the truck at the airport for a week or two. Where would I find the spec for normal draw when off for this vehicle? 80ma seems high. What stays on besides the clock and memory module?

 

After all modules have gone to sleep, 50 mA is the maximum draw fora factory-equipped vehicle per the service manual for your truck.

 

Thanks. That is helpful. It looks like the truck drawing at least 30 mA too much. Seems like a module has insomnia. Does the service manual call out the order of shut down of the modules? Does it point out likely suspects?

 

Check and see if the current is actually passing through the F21 circuit by inserting your milliammeter in the fuse slot. That's what you were chasing...

 

The current is not going through fuse 21. I have verified that there is now no change whether fuse 21 is in place or removed. I have also checked every fuse in the main distribution box. No change with removing any of those fuses. This leads me to suspect the load may be from the subpanel by the passenger door but am not sure yet. So far I have been measuring current between the battery post and the cable feeding the distribution box. On the left side of the distribution panel there is a junction where the feed comes in from the battery. At that terminal there is also a heavy lead heading toward the rear passenger side of the vehicle. Is this the feed for the sub-panel by the passenger door? If so I can see if I can verify that the extra load is coming from the sub panel and not the main distribution box.