2001 F250 electrical issue.

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Vehicle is a 2001 F 250 with a 7.3L diesel and an automatic transmission. So I have been having some gremlins in my truck, not sure what it is or if they are even related. One day I came out and my blower motor was on. It actually killed the battery but once I charged them back up the problem went away. I didn't think much of it. But the other day I came out and the blower motor was running again. I could turn it off but I also noticed that the airbag off light was illuminated, all of this while the keys were still in my hand. I have just been leaving the climate control system in the off position for the past week or so to keep the battery from running down. But the airbag light still stays on. On the way home from work today, the speedometer stopped working. And about 2 miles from the house it came back, bounced around a little bit, and then stopped working again. Every now and then I can hear what seems like a relay behind the radio clicking when I'm messing with the climate control system, (turning it on and off) and when I do that the airbag light dims and brightens up.

Like I said, I'm not sure if any of this stuff is related or not I'm just stumped. A year or so ago I had come out and my radio was playing. You guys said to change out the ignition control module and I did. It fixed that. I just wanted you guys to know a history of changed out electrical parts in recent maintenance history. I also have an aftermarket keyless entry and head unit. Both professionally installed.

ANY help is appreciated. Thanks.

Edit: Also, the dome light stopped working and the OD off light is flashing.