I have a 1991 buick rivera it has no heat from the heater. I have had the cooling system flushed. I changed the temp control module.But nothing Changed.wife getting cold in tennessee winter need help.does the body control module control the heater

Before you replaced parts did you feel the upper radiator hose ,as close to the engine as possible , From a cold start you would be able to tell if thermostat was opening ,by change in temp ! Check heater hose's going through the fire wall to inside vehicle . When vehicle is warmed up are both hose's hot to the touch ? I would suspects the temp . gauge before the coolant temp. sensor , Because I know GM has had problems with the stepper motors that control the gauges .
The instrument panel cluster (IPC) displays the engine coolant temperature (ECT) as determined by the engine control module (ECM) or the powertrain control module (PCM). The IPC receives a class 2 message from the ECM/PCM indicating the ECT. The range on the ECT gage is between 60-125?°C (140-260?°F). The ECT gage defaults to 60?°C (140?°F) or below if the ECM/PCM detects a malfunction in the ECT sensor circuit. Refer to Cooling System Description and Operation.
Class 2 is a serial data communication network ,found on GM vehicles , Vehicle computers share information on this network .
How's the antifreeze ? does the vehicle still have the original dex-cool antifreeze ? You haven't change the coolant with green coolant ? Dex-cool an regular green coolant don't mix , they gel up clogging heater cores ,passages in the engine block etc...

Did you check to see if coolant is getting to the heater core? Most reset to default when the battery has been disconnected.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_4c166ba81493f541

could be an air lock in the heater rad, back flush with a hose to clear.

Check the PUMP, there is apump that pumps the coolant from the radiator into the engine, if its broken you will have that problem.

Flush the heater system.

Let me add a new twist. My 2003 has a bad heater/A.C. control module. Try moving the fan speed from off to 5 as fast as you can, like 5 times then see if you have heat or not. I bet you do.

Good chance your water pump is shot! Might need to flush entire cooling system, which includes the Heater Core. Let me know if I can help you with more details if needed.

the resister only changes the fan speed
if you have not heat
first check coolant level if it's down then you have a leak that will cause no heat if it's ok
then run the vehicle and make sure the engine temp gauge reads about half if not change the thermostat if the engine temp is ok
then grab the heater hoses see if they are hot then the heater core is plugged and if the heater hoses are hot
then there is a problem with the heater control head
hopr this helps

Make sure the temp door is moving when you change the temp.then change the thermostat out with a new one.Bleed the system of all the air in the cooling system.If still,no heat,remove the heater hoses from the heater core,and flush the heater core out with a water hose.In one pipe,it will flush out the other pipe of the heater core.

i mean heat and cooling for the seat, which control are on the door