[BigRock91]

On 90's Dodge trucks, how is the "Max AC" button wired different to the "regular AC" button.  Does it make the compressor come on more often or what is it supposed to be doing?

 

[dodge82273]

if you cannot see read photos let me know .

 

[ToxicDoc]

To simplify it, with max AC the air flap is closed, using only interior air. With regular mode, the air gets mixed with outside air to refresh it.

 

[DODGEBOYS]

yup MAX AC is the same as "recirculate" in a newer vehicle 

 

[dodge82273]

also shuts off the hot water valve

 

[BigRock91]

if you cannot see read photos let me know .

Very Interesting. Thanks a bunch for that diagram

OK that explains a lot then.
My friend's '90 regular cab (D150) cools great with the max AC switch on. My '93 RC does not. It's the size of the area it needs to recirculate in. With new air coming in the norm AC switch works best in my RC, especially under 100 degrees. The bigger the area, the longer it's going to take to recirculate. I had to re-do my whole system this summer, so I'm starting to notice things like this after all this time.

 

[dodge82273]

Very Interesting. Thanks a bunch for that diagram

OK that explains a lot then.
My friend's '90 regular cab (D150) cools great with the max AC switch on. My '93 RC does not. It's the size of the area it needs to recirculate in. With new air coming in the norm AC switch works best in my RC, especially under 100 degrees. The bigger the area, the longer it's going to take to recirculate. I had to re-do my whole system this summer, so I'm starting to notice things like this after all this time.

I'm not much on A/C myself , but , older brother use to use a thermometer in the vent , seems it is a matter of how cold the air comming out IS .... like a big house with a small window unit ? blows cold but ....