Short story

Last week taking a turn ,the door ajar light flickered. That same day when I armed the alarm the screen shot back at me saying the passenger door is open (it was closed).

Now when my stereo is off (OEM tape deck) the door light come on. I turn the radio on and the light goes off.

I am pretty sure the owner before me had a system in it and took it out before selling the car. But I've pulled out all the old wiring he left in it.

I pulled the HU out to see if any of the wires were opened up (none found). I checked the wiring on the passenger door no wired opened up. the speaker wires were spliced but done right, with no exposed wire.

Any ideas guys ??

Thanks in advanced.

P.S.

I also cleaned the connector for the door switch male and female ends and still comes on