1998 F-150 4x4 AC always on?

No, I don't believe that it's on all the time. Up until a week ago, i would get only external air into the cabin when I had the switch on Floor; Panel/Floor; Panel; or Defrost settings. Now, the only way to turn off the a/c is to turn the panel switch to off. I checked the A/C clutch relay (47A if I remember correctly) and it's okay. Still looking for the answer. I'll post it here when I get it fixed.

This is not normal, my '98 Explorer Sport just started doing this last month. 2-3 MPG loss and air on all the time (except in the "Off" position). I pulled relay #2 (AC Compressor control relay) from the under hood power distrobution box and left it at that. It sounds like the temperature control panel board is shorted or wornout. Will follow up when I find the cause....

I doubt SERIOUSLY that there is a problem. Most auto manufacturers lately
have set the compressor to run on most settings. Why? To remove humidity
from the cabin. It makes sense that if you need to defog the interior of
your windshield, that you have excess humidity. Most of the time, the
compressor is off on the vent setting and the floor only setting. Any blend
between floor and defrost will get the compressor. I can see the logic of
keeping the compressor on when in the floor setting though. Usually floor
is used for heat in the winter, one of the hardest times of the year to keep
moisture from collecting inside the car (because of snow tracked inside)

CJB

The ac in my 99 ranger runs regardless of temp setting in all positions
except 'floor' or 'panel'. Anything else and ford claims its dehumidifying.

It is just lazy.

"The OTHER Kevin in San Diego" <skiddz "AT" adelphia "DOT" net message ...

This would be FAQ, if we had one. It's been asked 100 times. It's made that
way, and that's about all you have to say.

Well if that's how its made I'm not impressed. What I am going to do is
install a switch and turn it off when I want it off and see if my gas
mileage improves.

Thanks to everyone that replied.

I believe you can control that by turning your temperature control setting
down just a bit. We own Fords exclusively, and in both my '99 F350 and my
wifes '03 SportTrack and '04 Explorer, there is a mark on the temp faceplate
where the compressor goes off.

Maybe not on yours, but maybe that'll help.

Spdloader

...

Andyou will defeat the functionality of the system. It doesn't
matter if you are heating or cooling. The output is a blend of both the
heating system and the cooling system. The only thing the temperature
control does, is control the register that determines how much hot air
is mixed with the cold.

I decided to just leave the AC system alone and not install a switch.

Thanks to everyone for all the great input.

Most japanese vehicles seem to have a button to turn the compressor on
and off. I guess the american manufacturers don't trust us to use this
properly. What a total waste of fuel! I like being able to run hot air
on my windsheild without the compressor running.

--
Rob Munach, PE
Excel Engineering
PO Box 1264
Carrboro, NC 27510

You are proof that they are correct.

What a total waste of fuel! I like being able to run hot air

Defrost or demist is the one time when it makes sense to have the compressor
running because it dehimidifies the air. Do you have any idea what happens
when you blow warm moist air against cold glass?