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There is no heater control valve on this vehicle. If the heater is not blowing warm then there is air in the system. You could also have a leak. Common leaks are at the bottom of the throttle body you will see to coolant hoses attached to the t-body this is the t-body preheater and they commonly leak. Try to bleed the air out of the system. This is how you do it.
Remove the bleeder screw on the top radiator hose. the hose goes across the top of the radiator shroud.
Locate the resvoir overflow tube it is a balck plastic tube about 6" long. Rotate it up so the end of it is pointing straight up.
Remove the resvoir cap and make sure the coolant is full. Put your hand over the cap hole so it seals it.
Blow into the resvoir over flow tube with your hand over the cap hole until a smooth stream of coolant comes out of the bleeder on the top radiator hose.
Keeping your hand over the hole once all air is out put the bleeder back in and tighten it down then you can remove your hand. Dont tighten bleeder too tight it will easily break.
While doing this make sure the resvoir doesnt run dry or it will put air back into the system.
If this doesnt work then you will have to reverse the heater core hoses.
Look on the passenger side firewall and you will see 2 1" or so diameter hoses.
Cut the rubber piece that attaches these hoses together being careful to cut right in the center and not cutting the holes in the hoses.
Then remove the clamps on each of them on the engine side where the hoses go to the pipes. Pull them off and switch them. This will reverse the flow of the heater core and get the air out of it. You dont have to switch them back it will not cause any problems.
Make sure there are no leaks in the system as it can cause air to get in it again.