My AC Isn't Working!

[HammerDown]

Ok, so it's 5 degrees outside but this is the first time in 27 years I pressed in the pretty little blue AC button and the AC Clutch didn't engage...***!
BTW, during the winter months does anyone remove their AC belt?

 

[The Warden]

IIRC the a/c system's intentionally designed so that it won't cycle if the outside temperature's below freezing...I think the owner's manual makes mention of that, but I don't have a manual onhand at the moment. I don't know how that's handled, but maybe the system pressure gets too low for the switch to cycle the compressor in cold temperatures.

I would wait until the truck's warmer (either wait for warmer weather, move the truck into a heated garage, etc) and see if the system starts working again. If it doesn't, unplug the compressor cycling switch on the receiver/drier and jump the plug on the wire side. If the compressor engages, either the system needs to be recharged or the switch went bad and needs to be replaced. If the compressor doesn't engage, either the plug at the compressor came unplugged, the compressor clutch went bad, or there's an electrical problem.

Hope that helps some...good luck!

 

[DaveBen]

I use the AC to defog the inside window. It removes the moisture from the incoming air.

Dave

 

[F350camper]

With temps that cold, I doubt the refrigerant is at a high enough pressure to engage the low pressure switch.

 

[The Warden]

I use the AC to defog the inside window. It removes the moisture from the incoming air.

As I understand it, that's one of the two primary purposes of running the A/C with the defroster...the other is to ensure that the A/C compressor spins a bit and keeps the seals happy. However, as Rob pointed out and I said in my first post, there is a temperature point where the A/C will stop cycling even when everything's working properly.

 

[icanfixall]

Way back in around 1967 or so ALL ac units had to function in the defrost section. Reason for this is hot air with moisture in it wont defrost the windshield as fast as the ac moisture free air will. This is why when you switch to defrost the ac pump begins working. It drys the air being pushed up to the frosted up windshield. Not the outside but the inside.

 

[Diesile]

Yep. My '94 F350 is a plow truck and it is -8F out as I write. If I bothered to start it (I won't) you would hear the engine off and on picking up the compressor load. Big help with defrosting.

 

[dunk]

Never had defrost issues with other vehicles but my current truck defrost sucks. In part because the windshield needs to be resealed so some moisture finds it's way in during heavy rain, and also because the blower motor doesn't move much air. In any event, try it next week? My girl's new foreign junk the wipers have stopped working in single digit temps, double digits works fine. Try it next week during the heat wave?

 

[HammerDown]

Way back in around 1967 or so ALL ac units had to function in the defrost section. Reason for this is hot air with moisture in it wont defrost the windshield as fast as the ac moisture free air will. This is why when you switch to defrost the ac pump begins working. It drys the air being pushed up to the frosted up windshield. Not the outside but the inside.

So if I moved the lever to "defroster" the AC clutch should engage?

 

[snicklas]

So if I moved the lever to "defroster" the AC clutch should engage?

I believe it should Ray..... However, with yours being an 87, the only year with the "Blue A/C Button" it may need to be on defrost and have the button pressed.

On my 03, it has the Automatic Climate Control, and it has an A/C button also. I can turn on and off the A/C compressor no matter what the setting. It will, when I press the defrost button, turn on the A/C which I can hear/feel and there is an A/C light on the panel, but I can also turn it back off if I choose........

Hopefully someone with an 87 with Factory A/C can confirm 100% how this is supposed to work........

 

[icanfixall]

Yes. If any defroster is used on any cars or trucks the ac pump will engage. As for extreme cold I really can't tell you it may or may not come on. I have never experienced cold like you describe. Might check on utube or goggle it and get a better answer.

 

[79jasper]

I doubt these old trucks have a sensor like that.
Even my jetta will run the ac below freezing.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[BrianX128]

My 90 kicks it on despite negative 13 this morning. My 250 which is an 89 also does. Not quite as old but still.

 

[HammerDown]

Well, I'll be heading outside to do the "defrost lever" experiment.
It's going up to 33 today and 56 tomorrow.
Just curious as I mentioned prior, on my '1988' the AC clutch always engaged, the truck still has the OE compressor but I honestly can't say I ever used it in these sub freezing temps.
Over Christmas it was almost 65 degrees, I did use the AC to just 'work' the system.
Oh and BTW two summers ago and not sure 'if' this has anything to do with it but...the system is now R134...in the summer it's cold like a meat locker!
As always, thanks for the feedback fellas

 

[Black dawg]

Ok, so it's 5 degrees outside but this is the first time in 27 years I pressed in the pretty little blue AC button and the AC Clutch didn't engage...***!
BTW, during the winter months does anyone remove their AC belt?

Do you have a way to check pressures? It wouldnt have to be very low on refrigerant at that temp to not close the low pressure switch. Could be a goofy low pressure switch to.