heater control valve

While I can not say for sure, it appears your 1998 Ford F-150 does not use a heater control valve. I am assuming you mean the "Hot water valve" which would turn on and off the flow of hot water to the heater core. I do not find a parts listing for a water valve for a 1998 F-150 so my guess would be that it does not use one - most new vehicles do not use hot water valves any more.

Oakman is correct. There is no heater control valve. I have the same year and modle F150 and I too was searching for it.