hello everyone I have a 2000 Volvo s40 with about 130k on her. The problem is that a few months ago my seatbelt went slack and then went taunt. This happened while she was in a parking spot I paid no mind to it until, the seatbelt would not retract and was stuck (the seatbelt failed), also the airbag light came on. So i parked her and decide to find a used seatbelt. A few days later I found one in the junkyard not too far away from where I live (the replacement belt worked fine it would give slack and retract did not seem damaged nor the explosive charge went off) so I ended up replacing the seatbelt myself. Was not too hard of a job just removing some panels and a simple plug to disconnect, swapped it out and swapped the new one in. I was in and out in 5 minuets really simple, but the air bag light did not turn off. There was no doubt in my mind that the old drivers side seatbelt was bad it would not retract nor give slack and when i replaced it I could see that the old belt ended up knotting it self up. The real problem is why wont the SRS airbag light shut off? I thought I might have messed up so I double checked my work, I redid the job and still the light will not shut off.

The car was NOT in an accident.
Airbags NEVER deployed.
I disconnected the battery when I switched out the seatbelt.(both times)
Put new seatbelt from another 2000 Volvo S40 that was not in an accident nor did it experience airbag deployment.
Reconnected the plug.
When I start the car the SRS airbag light will shut off for about a second or two then pop right back up.
All the other seatbelt's work fine.