I have a 2000 Blazer. Just purchased used last week. What is the small red bulb mounted on dash in the right hand speaker? It doesn't light up under any circumstance. My Ford F-150 has a similar device within the security system and it is always blinking.

Mark

 

If i'm not mistaken that is a sensor for the headlight and daytime running lights, start it up and have a buddy look at the headlights, put your hand over it and see if your buddy notices a difference in the brightness of the lamps.

 

x2. Automatic Head Lamp sensor (AHL). Senses when it gets dark and turns headlights on. No burnt out bulbs.

 

The security light for your truck is part of the instrument cluster and reads 'security'. Like everyone else said, that is the AHL sensor.

 

Thanks guys for the help. This site really works! Mark