Car thinks I'm stealing it

I have a 98 Mercury Mountaineer and the receiver doesn’t seem to read the coded key. On numerous occasions when I try to start it the theft light will flash and the car won’t start. I have puchased a new key so I know that’s not the problem. Is there any way to disable this feature?

Is the new key programmed to the receiver? Most times new keys won’t program from the original frequency. Disable? Don’t know.

I had the new key made at the Ford dealership. Also the problem started before we had the new key made, and it persists with the new and old keys.

At the time you had the new key cut at the dealer, did you mention the problem with the receiver? You MAY need a new receiver module and reprogramming, OR you may need the security system checked.