1992 Buick Lesabre heater control valve?

Check the coolant thermostat to see if it is stuck open(normally closed for a cold engine coolant)

It's a little spring valve located on the engine block by the upper radiator hose, they cost around 2-5 dollars to replace

Thanks HIDDENFALLS for trying. I looked at the thermostat housing you mentioned, but BOTH radiator hoses are hot, and engine is reaching normal temperature, so I don't think there is an engine thermostat malfunctioning here. And, there is NO vacuum hose, or even a wire to this thermostat housing, to control anything. I'm sure it's temperature controlling the flow to the RADIATOR, and not the heater core. Also, I should have stated, the TOP heater core hose is HOT, the bottom is only warm. I'm wondering if this model LeSabre even HAS a heater control valve, or if the mixing door (which works fine) is the only thing controlling the amount of heat brought into the passenger compartment. I'm leaning towards a gummed up, or clogged core. BUMMER of a job! Thanks. Rob.

I guess this was a 'tough one' as I didn't get many replies. I found the problem, and it was something I didn't want to do, but I finally replaced the heater core itself. VERY hot air coming into the passenger compartment now. It appears GM has gone the cheap route, and no longer puts 'heater control valvles' in these cars, but simply controls the temperature via the 'mixing door' which was (as I initially stated) working fine. This means clogged cores will be more and more common, as coolant, and all the goop that normally clogs old radiators will now be clogging heater cores, due to coolant ALWAYS flowing through them, not just when the heater control valve alllows collant to heat the core. Cheaper and cheaper.