Where is the heater control valve located on a 98 jeep grand cherokee?
There are two hoses that come from the thermostat at the top end of the engine at the front of the car. These two hoses go back to the firewall. Just above where they enter into the firewall there is a vacuum switch. It has two small hoses feeding it. One of the hoses gets its vacuum from the intake manifold and the other gets eventually fed to the heat control valve. The heat control valve is located on the opposite side of the firewall. You will notice that when the engine warms up the top hose is much hotter than the bottom hose. Upon start up the bottom hose might be moderately warm because a small amount of warm coolant will flow through it. After the engine is warm this coolant flow will stop because the heat control valve is closed even though you have the heat at maximum. Simply unplugging the electrical connection to the vacuum switch will open the heat control valve and you should have heat inside your vehicle again. You can also bypass the vacuum switch by unplugging both va
