Problem w/ intermittent defrost a/c
 

Have a '11 Crown Vic with 290k miles and I've been having a problem with the windows fogging up all the way around. The defrost seems to be working about half the time. On humid rainy days it'll work for say a half hour keeping the windows clear, then the windows will fog hard for 10-15 mins. And then it might decide to start working again, back and forth it goes. When I started it just now the compressor clutch turns when the a/c is turned on, although I haven't had a chance to observe it when the windows are fogging.


A secondary problem it has is that it only blows air through the vents on the front of the dash, straight out into the cabin. The air flows only very weak out the defrost vent at the windshield or the floor. It does this on all settings. Although this might contribute somewhat to the problem, it seems like the a/c does completely cut out as the windows will still fog hard with the a/c set to on and on full fan. When it cuts off the air in the cabin feels immediately humid. One that that helps somewhat is to turn the temp toward cooler and it seems to not fog as much and gives it a chance to maybe clear the fog some.


Any idea what's causing this or what I should do to start testing?

Never heard of a crown vic atv or utv!!

I think it was my Dodge van had a little door that moves back and forth to direct the air through different vents. If your car has that it sounds like it's stuck in one position like mine was.

Thanks. Actually if I can just get the intermittent defrost problem solved I'd be happy with letting the vent problem go.

Now that it's warmer weather I'm using the a/c now and it's showing the same problem as it did last summer. The air only blows medium cold, then cycles to barely cold, and then back again about once every minute or two. Not sure if this is related to my defrost problem or not.

Had a guy tell me earlier today that 70% of the time when you see a problem like mine it turns out to be what he called a valve inside the high pressure line that comes straight off the compressor, or condensor I forget which. Said you need a special tool to remove this valve from the line. Does this sound familiar?

I'm not gonna lie. I know diddly squat about A/C lines and valves.

Me neither, but I heard of this. General Chat. Ask for ATV help above in the Brand Discussions Area. Use this forum to discuss Life, Music, ETC. Or discuss pretty much anything BUT no political or religious threads. There's an area for that. :p

Expansion valve is probably what they're talking about. As for special tools, I can't say for that model.

You might need a line wrench.

I'm gonna assume my problem is being caused by low refrigerant and take a shot at fixing it as cheaply as I can. But at the same time I'd like to take steps at identifying where the leak might be.

So what will this look like? Renting some gauges from the local car store and checking my refrigerant lines? How would you go about this and what readings should I be looking for?

And then if things read low I would get a can of refrigerant with leak revealing dye and put it in the system?

Sorry I'm so remedial here, first time working on an a/c system.

Hooked the gauges up and it seems like I've got a low refrigerant condition. Before turning the engine on both gauges read about 75. After starting the engine and setting the AC on max you could really tell the compressor was cycling fast. The needles cycled every 5-6 seconds...one going up and the other down, then reversed. The blue gauge cycled between 22 and 38 PSI while the red went between 90-140. The outside temp was about 60 F.

From what I've read, especially with the compressor cycling so fast, this indicates low refrigerant. Hopefully my compressor isn't hurt by running it for so long like this.

How do I go about using this 2 gauge setup to add refrigerant? Should I add it through the middle hose somehow or get a can of 134 with a gauge on it and just add it directly from the can?

And how do you know how much to put in?