I have an 1999 F-150 extended cab. When I close the doors the cab light won't turn off nor the light above the back window on the outside. I have put DWD40 on all the latches with no effect. Any ideas? My door ajar light is not on.
Mel

 

I also have a 99 which had the same problem. There's a couple of small relays in the fuse box area. I took both out and switched them and the interier lights work properly, so I knew one had failed. I replaced the bad one and have not had any problems since.

 

The one inside the cab or the the one in the engine compartment?
Thanks
Melqui

 

Opps, see the you did read the sticky. Sorry guys.

 

Considering the note that the Door ajar light is not on when this his happening, I would check the Interior lamp relay, that Stephen_T made note of.

This could be a case of the Normally open contacts are not returning to the normal position.

Or

The other items here could be the Battery saver relay coil is not becoming de-energized by the GEM ground signal ( pin 1 ) or the Ground to the Interior Lamp Relay is not releasing ( GEM pin #15 )

Start with Relay #1 in the Central Junction Box, which is a half ISO relay.

Use a Half ISO relay from the Battery Junction Box ( under the hood ) from something like the Horn Relay (any of the relay 201 to 207 ).

Leaving the Battery Saver relay in place would point the direction of the problem ( int lamp relay or GEM / Batt Saver ) source.

If you need one of the half ISO relay, Autozone carries a major manufacture of these for an OEM option, rather then the 19.00 relay from Ford

 

Replaced the relays in the inside fuse box with no change. One more thing I did notice was the lights turn off after about an hour or a little more. The lamp over the back window outside is also staying on and the red light aren't working.
Mel

 

OK, I am going to ask the dumb question............

-> Did you make sure the interior lamps are not turned on via the dash dimmer / int lamp switch ?
I know it sounds like a stupid question, but just had another operational error on a Thread yesterday, and thought I should check considering you replaced the interior lamp relay, and the accessory delay relay seems to be doing it's job.

When you pulled the Interior lamp relay, the interior lamps went out right ?

When you say the outside lamp, I assume you are talking about the cargo lamp. That comes on with the interior lamps.

The red lights are not working, as in when you press on the brakes ( that is the CHMSL / 3rd brake lamp ).

 

Yes they do when I pull the relay out.
And yes the cargo white lights stays on as well but eventually go out. The red lights are not on.

 

Ok, so the Accessory delay relay is ok ( the lights go out eventually )

The lights are not getting a power source anywhere else ( pull the int lamp relay, and they go out ).

I need to ask again :
Q1. When are the red lights not on ?
1.1. When the brake is on ( that is the 3rd brake light / CHMSL and should only be on with the brakes ).

Q2. Did you check the panel dimmer ( dash, radio & HVAC dimmer ) on the panel, to make sure it is not in the full up position ?
2.1. This is how you turn on the int lamps, and if it is all the way up, clicked to on, the int lamps will be on, until the Accessory delay takes over.
2.2. Turn this all the way down ( rotate the wheel all the way down )

 

I went out to the truck to check the dimmer switch with dread. Yes it was on the up position DUhhh! My wife didn't know what it was so she was messing with it when she drove it to work. She is no longer allowed to borrow my truck!! Kidding...Thanks

 

No problem. It happens.

Did you happen to notice how long I had you chasing your tail in circles, BEFORE I asked you to check the obvious thing ?

It took me 12 hours and another thread to think of this, so I guess we are both Darwin award winners.

Glad it was an easy fix.