I know this is a common topic on here, I'm not just reposting it though. I went ahead and sprayed all of the door switches with WD-40 multiple times, and the interior cab lights still come on. So, I'm assuming one of the switches in the doors is bad. Only thing is, I don't know how to figure out which door has a bad switch. Does anyone know of a way I could check this? And if you think it may be something other than a bad switch, please let me know. It's annoying not having any interior lights (I took them all out to keep the battery from running down).

Thanks for any help!

 

Can you tell us what year and model truck you're talking about?

Modern door switches are actually latch switches. To determine which switch is bad, you might have to pull the door panel and backprobe the connections at the switch. Check for continuity with the door latched vs. unlatched. Do this for each door until you find the one that has no difference in continuity between latch open and latch closed positions.

Or, save yourself some time and just replace the driver's door switch. It stands to reason it is the one that failed since it is the latch which opens and closes the most.

 

It's an 2002 F-250 7.3l Diesel. Sorry about that forgot to include it. I may try to check the continuity and spend the extra time to be sure. I'd hate to replace the driver's door switch if that's not the issue. Thank for the help!

 

Make sure the dash light dimmer/interior light switch is not in the "on" position for the interior and box light. I had the same "problem". Interior lights/box lights would stay on for about 30 minutes then turn off (supposed to do that). I had unknowingly turned the dial to lights on position.

 

That's the first thing I checked, and unfortunately it was in the 'off' position, so that's not the issue

 

When I bought my 99 , my problem was the same, except of course I had. a " door ajar " light on as well .

The offending door switch was the passenger door.

5hey get sticky from less use.

 

If you've sprayed your door switches to put a 2AM drunk to shame, then you might have another culprit, and when I read the year I am willing to put money down that I'm right:

Your VSM might be faulty. VSM stands for vehicle security module, and is a little box in the middle rear of your dash, on the floor. You can feel it by reaching your hand around the center of the truck near the pedals. Ford had a bad run of VSMs for 2002, which is the first year they came out (2002-2003, I believe, are the years they put them in before moving back to GEMs) and they cause the following issues. Only one or all may show at a time.

1. Door ajar switches faulting throwing door open signals
2. Key fobs don't work
3. Power locks don't work
4. Radio stays on after the car is off
5. Automatic lights don't function

Probably something else I forgot about but I'll figure that out later.

The part you need to replace it is here:
Amazon.com: Genuine Ford 4C7Z-15604-AC Alarm/Keyless Lock System: Automotive

There ARE fuses you can pull and insert again to reset the system, but generally if you have to do that reasonably consistently, your VSM is starting to or has already gone bye bye. I think one of the fuses is 19. Someone will add those in later, I'm sure.

 

Just a quick post on this problem before you start disassembling your truck. I also had this problem. Just could not figure it out! Stopped at the Ford Dealer and had all the salesmen trying to discover the problem. No Way! Needs to go to the Mechanic was their solution. Then just by chance, with the click of my remote I felt it. The lock button on my remote was slightly tilted and it kicked back up and bingo the lights went out. CHECK YOUR REMOTE. Took my remote to Ace Hardware. We tore it apart and it was filthy...after 13 years you can imagine what we found. We cleaned the debris off the terminals, cleaned the rubber casing with alcohol and a Q Tip and around the buttons. Everything is working normally now. Hope this Helps. Linda

 

Ah I'm having this issue right now. I don't even use the remote for my ex or carry it with me. But my interior lights will not go out. I don't have a door ajar light on, I always slam the rear hatch. I'm thinking it's a relay or something. I went out for the night for about 5hrs and found my lights were still on. And the problem persisted none stop.

I removed relay 1 from under the dash and fuse 14 blew. I replaced the fuse and it's good for now. Going to find another relay to replace it with and see what happens.

 

I just had same problem. water leaked in from top of windshield causing short.
Patched holes and sealed windshield. no more problem.

 

I’m new to this forum and still learning, but thank you for that piece, I don’t know why I didn’t think of that. I checked all my doors twice. Rookie mistake

 

My overhead light will turn on when you open the door even with the overhead switch in the off position. I have to turn the switch on then off to turn them off. This started happening with the right rear door was replaced.

Don