The heater in my 01 Blazer does not blow very hot air. It gets up to about 210 on the temp gauge. Occasionally if I am running the heater it will cut out and then come right back on. Not sure if these two things are related but I am wondering where to start with diagnosing this.

 

sounds like your heater core is plugged. check and see if the heater hoses are both hot or one hot- one cool/ luke warm. if one is alot cooler, there isn't enough coolant flow through the heater core. also, check and see if there is a valve on those lines (sometimes they get stuck and restrict flow to the heater core)

 

I would pull & replace the thermostat. Its only 2 bolts and 7 bucks. Wrap rags about the area because some A/F will come out of the upper tube. Doing what derek said would confirm the stat failure. Good luck, my problems a little bigger. lol

 

I had the radiator flushed so if there was a clog it seems like I would have noticed it then. I am wondering if the heater control isn't bad. Is this possible?

 

Ummm.. no. Leave the thermostat alone, it only controls flow to radiator, not heater. IT DOES help engine warm quicker.
That's assuming your temp gauge does not go above approx 210. AND that...
When you check the radiator coolant level cold at least once a week, it is full to the cap.
That's very important in these trucks as most can attest.

Then Derek is right. Warm the car, turn on blower high. check those heater lines at firewall

1 warm, 1 cool - blocked
Both warm or othe r slightly cooler - probably the blend door actuator.

Search
blend door actuator replace site:blazerforum.com

Now as to 'cutting out'..what cuts out. the blower?

 

Yes the blower cuts out.