I have a chevy Blazer 2000 and the heater doesn’t gives cold air. I have the mechanic change the thermostat and heat pump, and all that did was to give a lukewarm air. I need help.
I’m going to assume the air conditioning (AC) on your Blazer is not working. A thermostat and water (no heat pump on a Blazer) replacement would not affect the AC. I have a 2000 Blazer, when my AC stopped working, I opened the hood and noticed the Compressor was cycling on/off every 5 to 10 seconds. The compressor is at the top of the engine on the drivers side. Cycling is when the clutch engages/disengages, that is, the front of the pulley on the compressor will engage and start spinning while the engine is running. Don’t get too close to the engine while it is running.
This could mean the system is low on charge or in my case, one of the pressure switches was bad. You might want to take it to a shop that specializes in AC repair for a proper diagnosis or even a GM dealer.