Useless thread on Climate Control er... controls... explained.

[doonze]

I know only about 5 people in the whole world will ever find this interesting and informative, but for all 5 of you, here it is.

This is of course specific to a 93 Explorer, but I'd think most other 1st gen 91-94's would be the same. This is the control that has OFF - MAX A/C - PANEL - PNL/FLR - FLOOR -FLR/DEF - DEFROST mode selector. The Push button A/C/Fan control and the standard Blue/Red temp control.

This is all verified on my truck through several different states of repair.

Firstly, if the A/C-FAN button is PRESSED, and the little orange light is ON, your A/C compressor is running and your condenser is condensing, irregardless of what other settings are on. So MODE can be OFF, and FAN can be OFF, but if the orange light is on your A/C is running, period.

"Now when does the A/C run when the light is NOT orange, and the button is NOT pressed" you ask? Well I'm glad you did! That would be when it's in DEF/FLR or DEFROST mode on the MODE SELECTOR. Once again irregardless of other settings if the selector is in either of those two modes the A/C is on. However the light will NOT light orange in those modes unless the button IS pressed. But then it's orange anyway so meh....

Moving on... outside venting vs. recirculated air, and the direct reason I know all this now for sure. The ONLY 2 modes you can use to get Recirculated cabin air is OFF and MAX A/C. ALL OTHER MODES OPEN THE OUTSIDE AIR VENT.

***If you get air from the vents even with the selector in OFF and MAX A/C, and the fan is also OFF, read my 2 threads about fixing this issue.
HERE
AND HERE
***


Also of interest, OFF and MAX A/C from all my test appear to be really the same thing. The only thing that changes in fact from OFF to PANEL when moving the selector is that when you get to PANEL it opens the outside air vent. So, if you want A/C or heat, recirculated and from the vents only.... OFF and MAX A/C both work the same for doing that. MAX A/C doesn't appear to have anything to do with A/C at all, heat works just as well in that mode. It only seems to be a PANEL setting where OUTSIDE AIR is shut off. I think OFF is just there to make us feel better. So if the mode selector is OFF, and you turn on the fan and hit the A/C button, you get cooled air from the vents. Same if you slide the temp control over to hot and hit the fan. Hot blown air from the vents. So OFF on that control means nothing.

The fan works normal. OFF IS OFF, and there are 4 speeds of fan. Push the button and it turns the A/C on, and the orange light comes on. Press it again and the orange light goes out and the A/C turns off. (except in FLR/DEF and DEFROST modes where the A/C is on no matter what the other settings)

The temp control is normal as well, nothing weird there. Blue is cold/Red is Hot.

Some other interesting facts. If LOW on the fan control is too much air for you, but you would like to have A/C cooled air flowing in the cabin slide the temp to cool, put the mode on PANEL and the Fan to OFF and press the A/C button. You will now get outside vent air cooled by the A/C. Course if you stop moving there is no longer any cool airflow.

If you can't seem to get it warm enough, or you want it to warm the vent air quicker, put it on MAX A/C, Fan on a setting you like, and temp control to hot. This will close off the cold outside air and use the warming up inside cabin air instead. So it will warm faster and get hotter. However you can't use this with floor settings, that opens the outside vents again.

As a side note, I've owned over 20 cars in my life, and this one has the strangest control system I've every seen on a car. My 68 Mustang was wack, but not THIS wack.

Just thought someone might search for this one day and it might help them figure out what is SUPPOSED to happen so they know if they got a problem or not. And also shed some light on how the silly thing works. I'm sure everyone who has a perfectly working system knows all this, but for those like me who had a broken system for 2 years and didn't know because I thought it was normal, this threads for you!! LOL

 

[TedJ]

This is a good load of info.

The controls are a bit weird, but they get the job done. I like the independent control of the A/C because I will run it in panel/floor mode or floor mode sometimes when I'm on a longer trip and don't want cold air blowing in my face.

I think mine might be different though for forcing the A/C on in floor/defrost. I'm pretty sure it only turns the compressor on when I put it in defrost mode. I like that better because often in the winter I just need to put some heat on the glass, no reason for having A/C then.

I think i read somewhere that there is just a little switch down at that end of the control which could be easily disabled. I can add my own a/c to the defrost if I need it.

I wonder if there is some kind of rule about having it that way? Every car I have ever been in and bothered to check ran the A/C in defrost. Protection against the lawyers for the idiots who couldn't realize they need A/C for defrost when its hot in the summer and raining?

 

[doonze]

I've noticed and wondered that myself Ted. As for FLR/DEF mode, I'm pretty sure mine was on in either mode, but it may be that mine is a little off, and throws the switch in both settings. If I can get a 3rd opinion I'll update the original post if needed.

As a side not, this post was hard to write, it was hard to explain. It's easy to think, but hard to say...LOL

 

[LXNavajo_94]

Actually there is another reason for the A/C coming on in defrost other than sending drier air across the windshield to evaporate moisture faster. It all stems from the fact on the earlier A/C systems they did not have the automatic A/C on with defrost so with the coming of the first warm day where A/C would be needed people would turn their A/C on and the compressor would be locked up. This is due to liquid refrigerant migration.


Without getting too technical here liquid always tries to find the coldest spot. In an Motor Vehicle Air Conditioner (MVAC for short) system in the winter the compressor will be the coldest spot at times. R-12 it is known to be a wonderful degreaser in liquid state. It used to be used in hvac systems to clean up after a compressor failure prior to the EPA banning this practice. Think ozone depletion and global warming.


During the winter months the liquid would circulate through the system where ever it was coldest and carry the oil with it usually depositing it into the condensor or the evaporator thus starving the compressor of oil. (Think starting your engine with a empty oil pan.) In a home A/C we combat this with a crankcase heater. MVAC compressors don't have provisions for this as it would drain a battery rather quickly to have a high wattage electric heater on when a vehicle is not running.


This is why a mvac system turns on the A/C during defrost. This accomplishes 2 things to keep liquid out of the compressor and oil in the compressor crankcase where it belongs. Granted not all oil stays in the compressor at all times. A small amount of oil is picked up by the refrigerant during normal operation, but does not hurt anything as it eventually gets carried back to the compressor. The oil charge in the system is adjusted for this. This oil carryover is a good tool to help find system leaks. Just look for oil trails on or near an A/C component.

 

[Roadrunner777]

Also, just adding to the 1 year old thread... both the OFF and MAX AC positions will turn off the flow of hot coolant to the heater core if your vehicle is equipped with the diverter valve (93 and 94, plus frequently retrofitted to earlier models). And, also assuming said valve and vacuum lines are intact and so forth. 17 year old parts.