I know this is the wrong time of year to need heat
but mine in my 1997 camaro dont work very well when the defroster comes on and the coolent guage never goes over 180 even on really hot days
it still has the stock t -stat and runs fine
what could this be
it used to run much hotter 210 230
this will not be good in the winter when i need the heat

 

You might need to flush out the heater core....

 

Yup flush the core. I had the same problem. Blower and everything worked just fine, but I couldn't get crap for heat. Take off the two lines that go through the core. Take a garden hose and flush water through them in both directions. Make sure both lines are off when doing this. I had all kinds of black and brown crap come out of the lines. After I got clear water when flushing in either direction I reconnected the lines. The heat works better than ever now.

 

where did you take them loose at
heater core or water pump/front of car

 

Water pump at the front of the car. Much easier to get to.