Well my A/C blew ice cold yesterday and today it blows hot as hell, never slowly lost any cooling ability and started to blow slightly warmer at all, just ice cold one day and hot the next.

The compressor is still spinning when I press he A/C switch on, but I hear a loud hissing behind the glove box, especially when I open the glove box. Is that where the evaporator is located? Why would it be making that loud hissing noice when the A/C was on? Is there anything else behind the glove box associated with the A/C that would be making this hissing noise?

Thanks.

 

Nobody knows what would be hissing behind my glove box that is associated with the A/C, evaporator maybe??

 

OK, let me re-phrase this.....Does anybody else have a hissing noise behind their glove box when the A/C is on?

 

if my a/c worked i would turn it on, good luck

 

Wow thanks for that gem. I don't even know what the hell that means, big help.

 

Year/Make/ Model ??
That would Deff help a bunch

 

Doh...sorry about that....'91 4Runner.

 

^^^^^^^

 

any of your lines have freon on them like a leak? i had an older xterra and one day i had ice cold air and the next hot just like you, i popped the hood to find the low pressure hose had freon all over it. i replaced the hose and recharged it and never looked back! as far as hissing my does not hiss!

 

Nope, I don't see anything on the lines, no oil around any of the fittings, they actually look brand new. The high pressure side is still getting hot when the compressor is running and the low pressure side is still getting cold, but no cold air in the truck.

The only thing out of the norma that started was the hissing behind the glove box. It always had a slight hiss, but it has now gotten a lot louder.

The compressor still turns right on and engine idles up, so I'm not sure what's going on.

 

Have you checked the operation of the blend doors in the heater/ac plenum? I can't remember if they are vacuum controlled or not. If the high side is hot and the low side is cool, the system must be working at least somewhat. Check to make sure the blend doors are doing their job.

 

The blend doors on the truck are controlled by cable, I checked them too, they work fine, plus I never moved it from Cold to Hot, so the doors wouldn't have moved.

Not really sure, this might just be going to a shop. I hate A/C problems.

 

if you get it figured out let us know............this perplexes me!

 

Be thankful it's September, it's gonna be heater season very soon, so you'll have all winter to figure it out. Check the clutch on the compressor, if it's not engaging, you won't have any A/C.

 

Could you have a leak in the evaporator?