How do I trouble shoot Fuse #21 in a 2005 Ford Expedition

I have been having trouble with my battery draining overnight. (e.g. 10 to 12 hours).

Placing an amp meter inline between the negative post on the battery and the negative cable. Letting it set for 45 minutes with nothing on, I pulled all the fuses, then started adding them back in. Got to Fuse #21, which appears to be related to the instrument cluster. If I leave fuse 21 out, the battery did not drain for two days. (note, this is with all domes, and accessories NOT on). yesterday morning, I went to work early enough I had to use my headlights. (flipped the headlamp switch to auto), drove to work, went out 8 hours later, drove home. Parked the truck. This morning (Saturday), went out to start the truck, and no go, it would not start. Noting, the ONLY thing I did different than Wed. or Thurs, was Friday AM in flipped the headlamp switch to auto. Now I am not sure if this has anything to do with the battery drain. But it looks awfully suspicious. Any ideas where I can go from here. and is there a way to 1) test the IC for issues that may be related, and 2) Can I bench test an Instrument cluster before installing it?

Thanks for any help/suggestions.

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Hi @roguemech ,

According to this link besides powering the instrument cluster, Fuse #21 also powers the courtesy lamps (as you've mentioned) AND the puddle lamps (outside mirrors). Can these be turned on/off at all. You may wish to check these as well.

Also listed in the manual is a battery saver relay R304 which should operate (release? - not sure which) to prevent the battery from going flat, in the event of a problem with the associated lamps.


Good Evening, the manual says that relay is not serviceable. any ideas why?

I had 11.9V on the battery when I finally went to bed last night. Checked it this morning (Sunday morning about 12 hours after I went to bed) , and it

was down to 10.6V. Went out of town, came back (about 10 hours later), and it is down to 9.3. I intentionally left the charger off, the headlight switch, the pedal adjustment switch, 4whd dial, and the instrument cluster (including fuse#21) all disconnected. And still something is pulling that battery down. I am also now wondering if I cooked the battery with all the dang recharges I did. Last night. that battery (around the negative side) was warm to the touch for nearly 4 hours. Not to mention it was out-gassing a fair amount as well.



Can you place an ammeter is series with the +ve cable to the battery to see what the current draw is when engine is NOT running and everything is switched off? (i.e remove +ve cable from battery and place ammeter between cable and battery terminal.

Most DMM's have a 10A DC Amps setting, so hopefully this is enough

Also you may have a double headed fault if there is still excess current draw with fuse #21 removed. You may have to start pulling other fuses.


Good Morning Jayeff, unfortunately, been there done that. After putting my Fluke 75 in-line, and letting everything go to sleep (about an hour or so), I removed the fuseable link between the alternator (and the smaller cable that feeds the alternator), and it seemed like all was around 20mA, the second I put the key in the ignition, it all jumped to 300mA, (and I confirmed this behavior with a shop here in town). I pulled every fuse, including the 5 black relays in the middle of the fuse box as well. started adding fuses back in. And the circuit seems to get the most excited when I plug fuse 21 back in.

I am headed out this morning to remove both the positive, and negative cables on the battery, run up a charge on it, then see if the battery starts draining without any help. Currently I still have everything behind the left section of that dash disconnected. The only piece I still have connected is the radio. But is it powered off.



You state that "I put the key in the ignition, it all jumped to 300mA,"

Does your vehicle have an immobilzer system installed which is controlled by the insertion/removal of the ignition key at all? This may explain why the sudden increase in current when you only inserted the key.

Most car radios have two power supplies connected to them. One is for the radio functions and the other is illumination. Just something to be aware of.


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