Yeah, but its all automatic and stuff. Maybe TX is different, but I've never seen a day when you needed both Max A/C (plus the mod) and Heat. I'd just put a manual valve in the line and be done and save some money (even though the dieselsite kit is only $60). Open it in the fall, close it in the spring.

 

"Big trucks"? About half the passenger vehicles built in the last 50+ years have heater control valves. My wife's old '83 F150 brown turd had one. Of those that do, some use a simple two-port valve that closes off flow to the heater core. Others use a four-port valve that opens a bypass from the heater inlet hose to the outlet hose as it closes the flow to the core, to complete the "circuit" while bypassing the heater core.

The Ranger heater control valve, typically used for this mod on our trucks, is an example of the latter. I reckon it's preferred for this mod because of something to do with how coolant flows in our systems, that you want that loop to continue flowing (whether through the heater core or not), and not just stop it with a simple valve. But perhaps that's not a concern, since as said, the dieselsite.com product uses a simple two-port valve.

 

This was my concern is stopping the flow. Does it just flow back on itself? Does anyone know what valve to use to complete the circuit, so to speak. The A/C is working great now,but any help on these 100* plus days would be welcome.