Want to get more out of your Air Conditioning on your 7.3PSD powered truck or vehicle? This may not apply to every vehicle but Ford Trucks are definitely designed where air flow for the air conditioner passes 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 cool are from your air conditioner to be up to 10 degrees cooler. 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 so when the Max AC is turned on the vacuum causes the device to re route the flow of coolant automatically.

Four Seasons 74809 Heater Valve

Vacuum powered sounds great but is also complicated and does it work 100%? Another issue is it only works when the Max AC is turned 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.

Both options require cutting the heater core lines to install the valve, however, the vacuum valve requires running 3/16″ vacuum line T’d off from the max Max AC valve on the passenger side near the right kick panel just above the end of the rug on Ford Trucks to the valve under the hood.