I have been searching all over the forums and still can't figure this one out. My dome/cargo lights will not work with the dash switch or when any door opens while the key is on. They do work when I use my key fob to unlock the doors or when I first shut the truck off. My door switches are working fine, I think, I get the door ajar on the dash when either door opens and it does not stay on when they are shut. but here is the weird part. When I start the truck with the door open, it locks the door like it is not recognizing the door is open I am guessing probably Gem module, But could it be vsm? How can I be sure, what do I test? It is really starting to drive me crazy. Please help.

 

There's a small relay in your fuse pannel under the steering wheel. Bottom or top I don't recall with 4 prong sticking out of the it where it plugs in. I had a random problem until one day it just went out and I could hear it clicking over the engine running. It's worth changing if you havent yet.

 

Thanks, I did try that too. no change.

 

The vsm relays are deep behind the radio. Basically at the firewall, pull radio and you can see the blAck cover. Size of snickers bar.

Cover just snaps over a tab on each end. I removed cup holder and entire lower dash to be able to remove the cover and relays.

No answer to prob. Sorry, not sure how vsm effects dome

 

On second thought the vsm may not be those four relays. I checked mine from all door locks quiting at once.

Once cover off I used key fob and touched each relay to see if they clicked

 

In me E99 I have 3 relays back there. There are 2 small ones and 1 larger one, not sure about the smaller two but the big one is your turn/flasher relay.

 

So could be vsm relays?

 

Give this a try, can't hurt. Spray WD-40 into the door latches on your truck, some dirt and grime could have gotten in there. But usually the sign of this fix would be that when you come to a stop the dome lights would turn on by themselves.

 

what year and model do you have?

 

It's in my signature. E99 F-250. My issue was a little different as the dome lights pretty much had a mind of it's own turned on coming to a stop, took of at about 15MPH the went off, turned off at key off door open, etc. Someone mentioned to spray a little WD into there and I figured can't hurt and fixed it up after I wired a toggle switch from the fuse box, go figure. Unfortunately to me yours does sound like it's also elsewhere.

 

I have an early 99 xlt ext cab.

 

It should be the same. It just locks into your rear door vs the crew cab locking on the post. I'm just trying think of a simple fix first before you start tearing your truck apart. Again the way you describe it the odds are slim to none but it can't hurt anything.

 

Almost positive its not the door switch, but thanks. Anybody have any experience with how to determine if this could be the gem or vsm?

 

I'm going to bump this, hopefully someone can chime in with a schematic. or go to search at the top center.

 

No ideas anybody?