99 blazer -heater out

our 1999 blazer has no heat and it is 12 degrees! can anyone help. we think we have to replace the thermastat???? We aren't sure how. Thanks! family is freezing!

if you have a water temp gauge in your dash, what does it get up to, if it warms to around 200 and then drops a bit and then comes back up to about 180-190 then the thermostat is good

I'm not convinced that the Tstat is your problem, but nonetheless I think it's time to do some cooling system maintenace. First thing's first, I'd go grab a Haynes or Chilton manual.

After, I would look at changing the coolant and doing either a prestone "flush" or "clean" depending on your preference. Many people on this board advocate the "cleaner" route as it is not as harsh as the flush. Now would be a convenient time to change that Tstat.

That said, it's quite possible that the lack of heat may be due to a blending door not opening/closing.

our 1999 blazer has no heat and it is 12 degrees! can anyone help. we think we have to replace the thermastat???? We aren't sure how. Thanks! family is freezing!
dont know what part of country you are from, but if you can stand being outside a bit, a coolant flush/cleaning sounds like a likely solution. that dexcool seems nice but it has a tendency to clog your heater core with gunk, restricting hot water flow thru core. had the very same problem and went out and replaced coolant with fresh dexcool. you will see two rubber hoses going thru firewall of vehicle, that is where hot water/coolant flows to and from heater core. i unclamped both hoses and ran my garden hose full force thru heater core outlet. flushed gobs of heat robbing gunk from heater core and then reconnected the lines and topped off my coolant. got plenty of heat now. you may occasionally have to flush heater core this way when using dexcool.(seasonally) GOOD LUCK !!!!!