AC is always on -1997 Ranger XLT/B-4000 had new AC compressor / hoses / dryer installed.

[cobrajocky]

I have a 1997 Mazda B-4000SE (same as 97 Ranger XLT 4L V6). I had a shop install a new after-market AC Compressor / all hoses / dryer on my truck during the late winter and I just noticed that no matter which position I put the dashboard selector knob in, it's blowing AC cold air. What could be the problem, something the shop did? How can I diagnose the cause?

I know motors, but clueless on AC.

Thanks

 

[RonD]

On the top of the AC compressor is a two wire connector, it activates the Electric Clutch to engage the compressor with fan belt
Unplug connector and then start the engine
If compressor is still "on" then the clutch is bad, always engaged, mechanical issue

If its off now then you have an electrical issue

The AC compressor should be on if AC(or AC Max) is selected on the dash switch but ALSO if Defrost or Floor/Defrost or Panel/Floor is selected, it helps dry the air in the cab, so there are 5 positions with AC on
There are only 3 positions when AC compressor is off, Panel only, OFF and Floor only

In 1997 AC systems the dash switch sends 12volt out(with AC on) to the pressure switches, if a pressure switch is "open" then AC compressor won't come on

After going thru the pressure switches the 12volts splits and goes to the Computer AND to the AC relay which passes the 12volts to the Clutch on the AC Compressor engaging it.

The AC Relay is a default relay, it always passes the 12volts to the compressor UNLESS its activated by the Computer to Cut Power to the compressor
Its called the AC WOT(wide open throttle) relay, computer activates this relay to cut power to compressor when you "floor" the gas pedal, this gives best engine power for passing or...??, for whatever reason the driver needed to floor it for, lol.

AC WOT relay is in the engine bay Fuse box



Temperature control in the cab is not related to AC on or off for the most part
Temp control is done by the Blend Door, in 1997 this uses an electric motor on a "door" inside the dash to direct air from the fan thru the heater core(HOT) or away from the heater core(COLD)
The Blend Door Actuator(motor) was a common failing in Fords, Rangers are no exceptions

So if you are blowing cold air with temp knob turned to HOT then its a Blend door issue, even if AC is on, which might be unrelated issue

 

[cobrajocky]

RonD
Tremendous explanation in every way - testing, operation and diagnosis. - Now I've got my work cut out for me.

I've read about the "blend door" failings on Ford Pups, my nephew had one go bad on his 2008 Ranger XLT 4x4 back in Illinois ..... not good in their sub-zero winters. So far mine is working on my Mazda costumed Ranger XLT; even though it's 22 years old, it only has 97k miles on it.

Thanks very VERY much on the AC "lesson", I'll be under the hood or in the cabin for a while.

 

[RonD]

If you pull off the 2 wire connector on either AC Pressure switch and compressor shuts off then you will know they are getting 12v from the panel in the cab
And unless some one has spliced in a 12volt wire to these switches, the problem will be in the panel, assuming it was in the OFF position



And just a heads up, in 1998/99 and up AC system wiring changed, the panel switch still sends out 12volts for AC but only to the computer
The computer then activates the AC Clutch relay, its renamed/rewired AC WOT relay, and computer activates it to send 12v to AC compressor from a separate fuse, doesn't use the Panels 12v
And pressure switches are now Grounds, lol, no volts