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MAX AC ASSIST AC Control Valve for 2003-2007 6.0L

This automatic heater core shutoff valve greatly decreases AC air temperatures
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Product Description

WORKS ON ALL 2003-2007 F250-F450 Diesel and Gas Engines as well. In the HD and Superduty trucks, hot engine coolant is flowing through the heater core whenever the heat or Air Conditioning is turned on. The system does not differentiate between the two. This is fine when you are running your heater.  However, running the Air Conditioner is a different story. When your AC is on, your cold air is not only flowing across the evaportator coil but it also flows past the heater coil which has hot engine coolant flowing through it. Even with the air flow diverted around the heater core, the heater is still emitting heat just like a radiator. This results in a very inefficient air conditioning system in these vehicles. 

This DIESELSITE Air Conditioning Control Valve will automatically shut off coolant flow through the heater core when MAX AC selected.  The result is a decrease in duct temperature by 10 degrees or more which will be felt through your vent openings into the cab. This gets COLD!    

Install takes about 15 minutes and requires no special tools. Everything you need is included in the kit. Full detailed instructions including color pictures are included. 

Check to make sure you do not have a factory installed valve - Some 6.0L engines came with factory valves as part of a climate control system. Vans, XL package trucks, and most early 6.0L engines usually do not have them.


Thanks for the info.  It's all hooked up and I can just about frost the windows. -- Tim J.

My A/C works like it should now. Thanks so much! -- Frank B.

Hey Bob, another great product. I have delayed a long time in ordering the AC control valve, sure wish I had done it sooner. Thanks for the usual quick order processing. You all might think this is funny, I am still doing mods on “Old Reliable” with 714,000 miles. I sure wish I could order another 02. The AC control valve has been one of those items on the wish list for a long time.  I always like to share my opinions about products. The products that work well, and are good improvements, deserve recognition. The marketplace has plenty of “snake oil” with false promises. I have been very pleased with every purchase at the Dieselsite.

Thanks again,  --  John A.

Q: Why does this only work in Max ac mode? And how do I make it work in all ac and vent modes?

A: The factory ac switch controls a vent door that diverts air across the coils through use of vacuum. The max and normal ac are two different positions. They are as isolated as heat and ac are. When you select max ac in the mode switch, vacuum is directed to the vent door that diverts all cabin air to recirculate across the evaporator coil. We use this vacuum source to operate the Dieselsite Max valve.

If you want to shut off the hot water flow to the cab in all ac and vent positions, an additional control is needed. This is what we designed the Cold Rush to do. You must have either our Max or a factory installed ac heater control valve for the Cold Rush to operate.