Explorer 2002 - "MAX" setting on AC switch not working

Are you talking about the "Max A/C setting"? If I'm not mistaken, this setting draws in outside air to help cool the cabin. . This is so the cabin cools down quicker. There is a vent door behind the glove box that opens for fresh air (Max A/C) and closes for Norm A/C. This is why when you have it on Max A/C it sounds louder, because the vent door is open which is right by the blower. If this door fails to operate, it is usually a vacuum problem. On my 99 XLT ( yours shoud be similiar) in the engine compartment for the SOHC V6, look by the black cylindrical A/C evaporator by the firewall ( or condensor I forgot what its called), there is a grey vacuum line connected with a right angle fitting to another line close to the alternator. If that connection looks good, check for vacuum problem elsewhere.

It is not a vacuum problem SORRY, but you have joined the ranks of us that have a broken blend door. It is a costly repair but if you are so inclined as to fix it yourself there are ways to do this. Just google explorer blend door fix and have at it.

Searcher PS... Its only going to get worse by the way, just wait until winter when you no longer have heat!

Actually, its the other way around, MAX A\C it recirculate the cabin air so it wont have to cool down the warmer (humid )outside air

I forgot to mention that your situation is how mine started, give this a try, as you turn the switch to MAX/AC slap the black box directly under the pass area, this is where the blend door is. If you hear the blend door swing into another position then there you go. Just because it doesn't, doesn't mean its not broke you may have to try it a few times. This is how I was able to get heat, once I had the door in the proper position I told SWMBO NOT to touch that switch. Now that it is warming up it looks like I am going to have to fix it the right way.

Searcher

Yes you are correct sir. I always get those two mixed up.

MAX A/C setting is sometimes no labeled correctly. Let me explain.

On days when the sun is out in the summertime and I park my vehicle out in the sun all day long the temperature inside my vehicle gets up to 130..maybe hotter. I then go to my vehicle to drive and open the door. What a scorcher. I start my car up and turn on the a/c. I do not put the setting on Max as that will re circulate the 130 degree air to cool it. What I do is turn on Normal which brings in outside air that is 90. Once the vehicle cools down somewhat to somewhere close to outside temp I then turn on MAX.

That is what I was meaning when I said MAX is not correctly labeled for all purposes. I just wanted to make mention of that procedure since a lot of people simply put it on max and think that is all that needs to be done.

I just wanted to add my comment to the conversation.

I hope the original poster gets his issue resolved with the max/normal.

Good luck.

Sam >

What you say may be true, but when the MAX setting works properly, considerably more air comes out of the AC vents, this on any of the fan switch settings.

On other vehicles I have had, the MAX setting had a special, high amp fuse that sent more amps to the fan motor and thus increased its speed, giving more air.

I had the rear blend door fixed last year.

WLW

Oh great theres a blend door in the back too?

I can't wait for that one to break!

Searcher

There is if you have a vehicle with dual AC.

That was about $400 for the repair. I paid the $50 deductable on my extended warrenty.

WWL

LMAO !!! Searcher that is funny. I can feel your anticipation !!!

Take care.

Sam >Oh great theres a blend door in the back too?

What the MAX setting does is open a door INSIDE the cabin, under the glove box, which allow the system to recirculate the air in the cabin

-- cooling it more quickly than if it was pulling in hot, humid outside air.

When that door opens, the system makes a lot more noise, so you may think the fan speeded up. But, it's just noisier.

My first guess is that door isn't opening. It is probably moved by a vacuum motor, so I'd look there, first. Don't know if you can get at the motor easily, or not. Probably not!

There may indeed be some increase in airflow but it's not because of any special high amp fuse or a super fan speed that works only on max. What happens is simply that it's a heck of a lot easier to draw air thru the inside inlet then it is to suck it thru the cowl inlet. With less resistance there is more airflow. And because the inside inlet is open it lets more of the fan noise into the cabin. That extra noise adds to the feeling that the fan is on a higher speed.

There is, on some vehicles, a separate power feed with it's own fuse for the highest fan speed setting and that's controlled by a relay. The relay is controlled by the fan switch. When the fan switch is put on the highest speed it pulls in the relay and sends full power to the fan. At full power the fan can draw a LOT of amps, more then can dependably be sent thru some of the inside the cabin switches without overheating the contacts.

"Max" setting is really just a setting that recirculates cabin air - it is NOT another fan speed. The fan seems to speed up because instead of drawing fresh outside air into the A/C system and forcing a like amount of old air out of the car, the fan just draws in air from inside the car and recirculates it back to the inside of the car. This is sort of like tying the fans exhaust and intake together. The fan as to do less work, so it speeds up. Most likely your problem is that the recirculate door is no longer functioning. This could be because of a vacuum motor (diaphragm) problem, a vacuum line problem, a switch problem, a broken linkage, a broken door, or a jammed door.

BTW, in general, the "Max" setting is not all that useful. If your A/C is in good condition it should be able to cool the outside air down to 40 degrees or so - the same temperature that it will cool the recirculated inside air down to. In fact, when you first start the car, it is better not to use the Max setting, since there is a good chance the outside air is cooler than the air trapped in a parked car. If you use the max setting you will have to cool the hotter air drawn from inside the car rather than forcing it out with freshly cooled outside air. Also, running on max for long periods of time can result in a build-up of humidity in the car. I think the biggest reason people like the max setting is the increased air flow because the fan is not trying to force old air out of the car with fresh outside air.

Regards,

Ed White

I think you are confusing the "max" mode setting with the highest fan speed. In the past many cars had a special direct feed with a fuse from the fan speed switch to the fan motor to power the motor directly when the switch was set to the highest fan speed setting. I've never seen a car where the mode switch included such a feature. For the last few Ford's I've owned, the mode switch (which includes the "max A/C" setting) wasn't even an electrical switch. It was a vacuum switch that directed the vacuum to the proper set of doors. On my old F150, the line to the recircualte door cracked, so I lost the Max A/C setting. What was worse, if you set the mode to Max A/C, so much vacuum leaked out that the mode changed from vent to defrost (the default position for the mode door).

Ed

First, thanks everyone for your input.

Here in Florida, when it's around 100 F outside and the sun is in full display, "MAX AC" has been the only way to get cool. This from when we first got the car -new. On occasion, we would change the setting to let some oxygen in.

I do see two vacuum ? lines coming from the engine compartment, going through the firewall and to the fan area. One connects to a cannister. Can't see where the other one goes.

When I turn this switch, I can hear the doors moving with the different settings, even when turning to the MAX setting. Also, the MAX setting makes it so you can't turn the A/C switch off - as it is supposed to do.

Will keep you posted.

WLW