General Motors produced the Jimmy S-15 sport utility vehicle between 1983 and 2005. This popular SUV went through two generations before being phased out. The first generation of Jimmy had a range of eight different engines, while the second generation settled on GM's popular 4.3-liter, fuel-injected engine. The heating system in the passenger compartment of the Jimmy includes the heater core, blower motor, heater control valve, electric fan and engine coolant.
Loosen and remove the negative battery cable from the battery with a box wrench or socket wrench. Place a plastic container under the radiator drain plug, open the drain cock with pliers or your fingers and drain the coolant from the radiator.
Disconnect the heater core inlet and outlet hoses from the engine side of the firewall using a wrench.
Loosen and remove the screws from the heater core case cover under the dash on the passenger side using a screwdriver. Remove the cover. A cabin light in some early models interferes with the removal of the cover. Use a wrench to remove the light's retaining bolt and move the light out of the way.
Loosen and remove the screws on the straps holding each end of the heater cover in place using a screwdriver. Remove the heater core carefully from under the dash.
Insert the tubes on the heater core through the back of the heater case and through the firewall, taking care to avoid damaging the tubes.
Install the straps on either end of the heater core and tighten the screws with a screwdriver.
Position the rear heater core case cover in place and tighten the screws with a screwdriver. If your Jimmy has a cabin light, put it back in place and tighten its retaining bolt with a wrench.
Reconnect the heater hoses to the tubes on the firewall and tighten the connections with a wrench.
Close the drain cock on the radiator and pour the coolant to fill the system. Attach the negative battery cable to the battery and tighten the connection with a wrench. Run the engine with the radiator cap off and add more coolant if needed. Make sure the overflow bottle is filled to the proper level.
