Most common cause is a shorted out light bulb. Look for a lamp that is not working & start there , next look for any frayed wires that may be rubbing on bare metal/frame. If the fuse blows immeadiately , the circuit is grounding out somewhere. If the fuse takes a little while to blow , then there is something in the circuit drawing too much power overloading the fuse.
A short in the wiring.
It would depend on what year the truck was made.
Is it blowing cold air only or not blowing any air at all.
Are you blowing fuses or are the bulbs blowing? Blowing fuses would be a sign of any wires or metal contacts in your brake circuit grounding out or shorting on themselves. You'll have to check all of the wiring in your brake light/switch circuit to be sure.
Dead short to ground in either: Parking light socket or wire to Tail light socket or wire to Dash panel lights Remove 1 bulb and/or socket at a time to try to determine which is bad
The ABS and parking brake lights on a 2002 Chevy Trailblazer may stay on due to a malfunction in the ABS system, such as a faulty wheel speed sensor, or issues with the brake fluid level or the parking brake itself. If the parking brake is not fully released, it can trigger the light as well. Additionally, a problem with the ABS module or wiring could also cause these warning lights to remain illuminated. It's advisable to have the vehicle diagnosed using an OBD-II scanner for accurate troubleshooting.
The light switch.
The torque converter may be cracked.
Is it the parking brake light or the ABS light? is it red light or amber?
Brake light switch defective or out of adjustment.
most likely the thermostat, but these vans also have a history of blowing head gaskets...... It would help if you described symptoms
Broken Belt?