I'm confused (not the first time).

I need to install a Heater Valve I presume on my 90 vert engine swap. The one that was there is gone (remember I bought this truck in boxes).

I'm not reinstalling the A/C, but of course all the internal vacuum controls are there for an A/C if I decide to put in one in the future.

On Amazon, there are two choices of Four Seasons Valves. From Amazon, "The 74612 is for vehicles without Air Conditioning. The 74803 is for vehicles with Air Conditioning."



That seems to contradict Rock Auto which lists the 74612 as WITH A/C.

Best I can tell, one uses vacuum to bypass, one uses vacuum to not bypass...the vacuum hose comes from the interior of the truck. I understand that vacuum is applied when the A/C is on, so would that be bypass or non-bypass? I'm thinking "bypass" as that would be the action? Or is "non-bypass" the normal off state. The use of the terms is confusing.

So, which one do I need for my truck, where I have all the stock controls, but no actual AC compressor hooked up?

Or do I say screw it and just hook the hoses direct and plug this vacuum line

 

Well, you could just plug the line from within, and either use a hand valve, or just leave it straight.

RwP

 

Robert,

Mine is a 87 with factory air. When the control is turned to cool, there is vacuum on the line going to the water valve. With heat, no vacuum.
Also, mine has the orig. valve and on top is a chrysler number 4085474 30505


If there is anything else I could look at and tell you, let me know

 

Perfect....that's what I needed. Was able to get a car quest one and confirmed it passed water with no vacuum. Thanks!