Hello to all, I have a 1998 4.2 F 150 XL with 130 miles. My blower motor for the AC/heater does not turn off when the ignition key is removed. There is also a beeping sound coming from the passenger side, it'll beep for about ten seconds then stop and repeat itself. I found the battery dead, replaced the battery and this started. I have also had a few problems with the ignition switch.

 

Very likely is the ignition switch.
It powers most everything though fuses and relays.

 

If the windshield is fogged, I would suspect a leaking windshield. It leaks on the driver's side and the water makes its way down into the gem behind the kick panel and in the dash. The leak can be so small you'd never notice it, but it will do things like leave the fan on. Usually you can just get the windshield replaced to fix it, but if left on its own for too long and you need a new gem too.

 

I had this happen to my 2003 FX4. Anytime it rained hard enough I would experience the following symptoms: if the fan controls were left on blower would stay on after key was removed, dinging noises coming from under the dash, wipers would work intermittently, dash lights would randomly light up (ABS, Airbag, Brake, etc.). After a few days of dry weather, it would usually go away. Had the windshield replaced early this past spring (had to have them remove the old one, clean all the rust and prime a few bad spots, then install the new windshield), and replaced the drivers side interior fuse box with one from eBay after seeing how corroded mine was. I checked the GEM module as well, and didn't see any visible corrosion. Haven't had a single issue since I had the windshield replaced. One of the rusted spots I had to clean up was on the driver's side, which was likely where my leak in the windshield was coming from. The water would get in, then fall onto the Gem/Fuse box and cause all kinds of electrical issues. If you've been experiencing these issues when it rains I would recommend getting the windshield replace and check your GEM and fuse box to make sure they're good.

 

Yeah, common LWS (lLaky Windshield Syndrome) symptoms. It's been a known issue for at least 15 years.