Having trouble with my long lost A/c , just got it back up and running after fixing Freon leak and now when I’m under a load or accelerating it blows out of defrost until I let up on the gas. Only happens on max a/c . The vacuum reservoir is good and the check valve inside is good and works fine at a idle and cruising speed. When I’m max A/c There’s very little vacuum going to the heater control valve and the recirc door does not open and also has little vacuum .

 

I know it’s not easy but 91 people seeing this and nobody has a clue ??

 

Welcome to the forum

Just saw this post

In MAX AC setting there are TWO vacuum solenoids added that are only used in MAX AC

Fresh air vent vacuum motor, and the Heater by-pass vacuum valve

In the engine bay there will be a Grey plastic vacuum hose that comes from the firewall, next to the black vacuum line that goes to vacuum reservoir, this grey line runs to the heater by-pass valve, it shuts off coolant flow thru the heater core for MAX cooling in the cab
Check that line is not broken and the valve "holds vacuum", and the line HAS vacuum in MAX AC

There is a vacuum activated door in the cab on passenger side that closes off fresh air intake for MAX AC, already cooled air is pulled in from the cab and re-cooled, instead of pulling Hotter outside air in and cooling it.

If either of these vacuum controls were leaking then you would lose some of the vacuum holding Vent doors in position which could cause the switch to Defrost Vent on acceleration


Diagram here: https://www.ford-trucks.com/forums/a...ntid=517&stc=1

Far right you can see the one vacuum line that splits to "grey" and the fresh air vent door
That one vacuum line only has vacuum in MAXAC

The grey line is the most common place to lose vacuum just because its in the engine bay so EXPOSED to heat and simply getting unplugged, lol.

 

To check these lines, would you put a hand pump on the lines to see if it holds pressure?

 

Sure thats a good way to test for leaks in hoses

 

So the white vacuum line going to the heater bypass valve and the recirculation door solenoid doesn’t hold a vacuum. And it goes deeper into the dash . Does that mean the actual control unit is bad/leaking ?

 

White line runs to the controller ****, so if you pull out the unit you can see if its leaking there if not run a new vacuum line from controller over to the passenger side and splice it

You didn't say the year of your Ranger?

Back of 1999 controller here, with vacuum hoses cut, so you can see white, black, yellow, blue and red positions: https://i.ebayimg.com/images/g/bZQAA...ha/s-l1600.jpg

 

Thanks man . I’ll have to check it out tomorrow and I’ll let you know how it goes . It’s a 97 2.3 2wd nothing fancy it’s still rolling down the road with nearly 300k on her

 

@RonD You’re a ranger genius, turns out there was a leak somewhere after the recirc solenoid under the hood like you said , not sure if it was the line or the heater valve but had full vacuum

 

Good work

Thanks for posting the FIX