Want to get more out of the Air Conditioning on your 7.3PSD powered vehicle? This may not apply to every vehicle but Ford Trucks are designed with the air flow for the air conditioner passing through the heater core first. If you can cut off the flow of hot coolant to the heater core when it is not needed then you stand to allow the air to cool up to 10 degrees more from your air conditioner. To accomplish this, many use a vacuum valve to cut off the heater flow to the heater core when the max AC is kicked on. This is not difficult to install and requires a split be installed on the max AC vacuum actuator line with a 3/16″ vacuum line from the valve under the hood through the firewall on the passenger side to the right kick panel just above the end of the rug on Ford Trucks so when the Max AC is turned on the vacuum causes the valve to re route the flow of coolant automatically.

Four Seasons 74809 Heater Valve

Vacuum powered sounds great but is also complicated and it may not work 100%. Another issue is it only works when Max AC is on. For those in regularly warmer climates this may not be enough. Taking some notes from International who manufactured the 7.3, they used manual control valves on their industrial applications such as school busses and box trucks for the same purpose. Following this lead, you can choose a manual path to achieve this as well.

Solid Brass Body 4-Way 5/8″ Manual Control Valve

Although manual, this valve is a true bypass and not a cut off so coolant keeps flowing even when the manual bypass is engaged. Turning the control valve twice a year (before cold season and before hot season) doesn’t seem like too much of a hassle and is easier to install.  Another perk of this bypass is that even your regular AC will benefit by not having to cool heated air.

Note that both options require cutting the heater core lines to install the valve.