Why is my door ajar light staying on?

"Austin Simpson, It is usually due to a sticking switch in the door latch #1 on diagram. Take some WD40, spray the latch on the door all direction especially try to get around #1 on diagram soak it, open and close the door firmly/hard 10-20 times and spray it again. This will most likely clean/lube up contacts. Follow up with a better lube graphite/silicone spray lube after a couple days. Check the link below, may help.

If no luck you may have to change the defective switch. Good luck.

I hope this helped you out, if so let me know by pressing the helpful button. Check

http://www.f150online.com/forums/electri..."

Don’t waste your time pulling the switch and cleaning it. Even when that works it is generally temporary. Replace the part. Also, as far as diagnosing which door, is the key in dinger also going off? If yes, drivers door. If no, any other door, but usually passenger front. It is not an issue with dirty contacts, but rather a plunger that gets sticky.

The switch may be physically broken and cleaning and lubing may not fix it, but of course it is a great first step in the troubleshooting process.