Max A/C, what's it's real purpose??

[Frank The Tank]

My 88 Rangers max a/c would blow hotter than regular a/c.

My 97- alternates between (floor, and defroster) then to main vent. then back to floor and defroster. It feels cold but it's like a rolling blackout of coolness.

Can somebody please explain what the deal is with "max" a/c because it doesn't seem to do much of anything. I tried it the other day at work, because it was so hot out, and the results were rather dissapointing.

Frank

 

[exbass94]

The only difference between "regular" AC and Max AC is that regular AC takes fresh air from outside, cools it, and blows it out the vents. Max AC recirculates the air in the cab, it doesn't take fresh air from outside.

 

[Earl43P]

If it is switching to Defrost, you have a vaccum problem.
Inspect the line going to the vaccum reservoir (either a black plastic sphere or an torpedo shaped one on the plenum). The connection at the reservoir is a checkvalve. When you lose vaccum, the HVAC defaults to Defrost.

 

[Frank The Tank]

Sounds like what's up. However it has never defaulted on regular A/C.

Frank

 

[Jay FX4]

I use Max AC exclusively. If it's working properly, it blows harder, and it's easier to recirculate the already cold air in the truck rather than continuously having to cool down hot outside air.
Also, if you're rolling by a skunk that's been spraying (or roadkilled), switching to Max AC gets the stench the hell out much faster.

 

[snoman6115]

wat about ac only blowing cold air on max? and it aint really that cold unless its blowing on my face

 

[oldjohnny]

I use Max AC exclusively. If it's working properly, it blows harder, and it's easier to recirculate the already cold air in the truck rather than continuously having to cool down hot outside air.
Also, if you're rolling by a skunk that's been spraying (or roadkilled), switching to Max AC gets the stench the hell out much faster.

Or, you can also switch off Max AC when you let one rip! I know I do!

 

[85_Ranger4x4]

I use Max AC exclusively. If it's working properly, it blows harder, and it's easier to recirculate the already cold air in the truck rather than continuously having to cool down hot outside air.
Also, if you're rolling by a skunk that's been spraying (or roadkilled), switching to Max AC gets the stench the hell out much faster.

If it stinks in your truck, you want to pump in fresh air, not recirculate the stinky crap...

 

[Jay FX4]

If it stinks in your truck, you want to pump in fresh air, not recirculate the stinky crap...

I disagree. The "stink radius" outside the truck will have to be endured for a longer period of time than would be if you immediately switch to max as soon as you smell it. I found that this method works best for me. The skunk population has gotten out of control here in my area, so I've had lots of opportunities to perfect the technique.....

 

[v8318cid]

Facts or opinions will probably vary on the function of MAX A/C, however, in my experience, its true benefit on newer 134a systems is that it helps the A/C system reach optimal efficiency faster. It does this by allowing the system to recirculate the cabin air which is usually going to be cooler than outside air once the system has been running for a few seconds/minutes, assuming you vent the hot air from the cabin initially by rolling down your windows anyway. Lower internal/cabin temps equal lower evaporator pressures. Lower evap pressure equals lower gas temps on each refrigerant cycle. I haven't used an R12 system in some time so I can't attest to the effect on those systems, but I'm sure its somewhat similar. Of course the skunk idea is just as valid...