I have a 2004 F-150 crew cab 4x4 lariat.

Last Thursday I was leaving the job site heading home. Super hot outside so I had the a/c on full blast. About half way down the road the a/c blower reduced in power to about 2/3 - 3/4 is what it felt like even though it was on the highest speed. I stopped at an event for a couple of hours. The truck was running fine (besides the blower) when I shut it off. When I got back in and started it up the blower wasn't working at all! The clock and radio were flickering and the dash lights wouldn't work. I started to drive off and then pulled over to check the battery cables just to see if they were loose and if there was anything obvious under the hood that was wrong. There wasn't. I tried to put it in Drive, but it wouldn't get out of Park fussed with that for a bit and even turned the truck off and back on and finally got it into gear. When I got home I realized my passenger headlight was out and my dash cam wasn't working, which has nothing to do with the truck other than it's plugged into the cigarette lighter.

This weekend I changed the headlight and the old one was shattered with pieces of glass in the housing. Now it works with the new one. I plugged my dash cam back in and it worked. I unplugged it and plugged it back in and now it doesn't work again. So weird. Even though no CEL, I had the idea to plug my OBD II reader in just on the off chance it might say something. When I did the blower for the a/c immediately came on and the dash lights work and clock./radio quit flickering. I unplugged the reader and the blower quit and the dash lights started flickering again. Plug the reader back all works again. WTF?!

I checked all my ground wires and they look fine from what I can see. I unplugged the battery while the truck was running to see if it was the alternator and truck kept running. Getting 14 V on the battery while running. Checked as many wires as I could under the dash and around the engine bay to see anything cut or chewed on or frayed, but nothing stood out; all looks fine. Checked all my fuses on the kick panel on the passenger side. None are blown. Not sure if I should try driving with the OBD II reader plugged in or not. Wondering if that would be a bad thing and cause an overload if something more serious would be bypassed....

What do you think? Any ideas? Has this happened to anyone before? I am open to any and all suggestions.

 

- remove batter terminals/cables and brush them all down, reinstall tight.

- have batt and alt tested at a big box auto store

- double/triple check grounds, especially on in passenger kick panel below fuses.

- disconnect any aftermarket stuff

- consider/check that last thing added/repaired or modified before problem started

- clear codes and then try driving using again, rescan codes.

report back with findings

 

I think your ignition switch is failing or has a bad connection

 



 

Yeah I would double check those grounds behind the passenger side kick panel.

 

I cleaned off all the ground cables I could find. I already did a thorough clean on the battery cables about a month ago. There was no CEL so no codes to erase, but when I plug in my OBD II reader it eliminates the gremlins. The A/C fan works again and the clock radio and dash lights work. I was messing around with it the other day and I discovered that if I have the climate controls completely off everything works fine. No flickering dash lights or clock radio. The minute I turn the climate controls back on the gremlins act up. Turn the climate off they go away or if I plug in the OBD II reader. So I'm thinking something weird is going on with the climate controls.

 

I did that and still acting weird.

 

The ignition seems to be fine as it starts and runs and drives fine. I was messing around with it the other day and I discovered that if I have the climate controls completely off everything works fine. No flickering dash lights or clock radio. The minute I turn the climate controls back on the gremlins act up. Turn the climate off...they go away or if I plug in the OBD II reader. So I'm thinking something weird is going on with the climate controls.

 

Interrogate the ignition switch
Means
Get it running with some of the accessories on like the A/C and radio
Then fiddle with the ignition switch back and forth until it dies and starts running again
See if you can get it to stay running while some accessories quit
Monitor system voltage why you play with the AC controls

 

Let me say it one more time. The ground lug behind the passenger kick panel. Make sure it's solid. These symptoms are 98% cause by that ground being rusted off.