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?

 

Most likely your window fog is because the A/C system isn't extracting humidity from the incoming air per its design. Have you have the A/C system checked for proper refrigerant charge?

Also if you can't maintain air flow as directed by the Function Control that tends to point to a vacuum issue within that system.

 

Thanks for the reply JWA. And sorry it's been so long since I dropped this. LIfe got complicated all of the sudden there.

Now that it's gotten warmer weather I've used the a/c a couple times and it's doing exactly what it did last summer. The air temp is only medium cool then it cycles up to slightly cool, and back again about every minute or so. Is this also indicative of refrigerant charge?

 

I answered you on another forum for the same question. We both came up with the window fog was due to the heater core leaking, and you replaced it

I answered today, and ask if you had put gauges on your a/c to check to see if you had enough Freon in the system.

Would be cool if you answer back on the forum where you first ask the question for a follow up.

 

Thanks for the help skuzzy. Sometimes I ask my questions on multiple sites as the answers can vary quite a bit and the correct answer can come from the most unlikely of places...and I get my wires mixed up as to what forum I'm on with answer, etc. So thanks for your patience and helping me nurse my old car along. I'll be getting the freon checked first thing.

Assuming it has a leak somewhere, how do I go about identifying where it's coming from?

 

Probably it's O-rings. Get a can of Freon with dye in it, and put it in, let it circulate in the system good

wait until dark, use an old school black light, look for the green dye at any fitting, you found your leak

At that point, you will have to evacuate the system, put in new o-rings, vacuum down the system and recharge.

 

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.

 

From some bad experiences and some conversations with an A/C guy, I've come to a few conclusions --not guaranteed to be correct.
1. Freon can help if your system is just a little low. I think that the R134 systems are more prone to leak and who knows about the ones newer than that.
2. If you're not careful, you can overpressure your system and damage something. The refill kits usually come with one gauge. A/C guys use 2, but they know what they're looking at.
3. When an A/C guy fills your system he will vacuum it out first. to get air out of the system. Air can enter when the freon is low and it will probably prevent you from effectively filling it up.
4. If you measure the temp of the air the vents when the a/c is on and it's in the low 70's, you're probably getting all that you ever will for cooling from the compressor. You might not be getting all of the airflow that you want.


You might be money ahead getting a reputable guy to evaluate your system. Find out what they wo;; cahrge to just check it -- might not be too bad. ALso, you can read up on a/c systems(maybe you'll get more out that than I ever did).

Good Luck,

hj

 

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 cycled between 90-140 PSI. 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?

 

After I took the gauges off I noticed one of the schrader valves was hissing, and now the system is down to 0 psi. So I believe a faulty valve has been the culprit all along.


Now that the system is down I'm going to replace both valves, but my regular schrader valve removal tool won't fit down on the valve. The stem of the valve is too long and the tool won't go down around it to twist it out. I need a tool with prongs longer to fit down into the recessed sides of the valve. Does this '11 Crown Vic have schrader valves or a different kind of valve?


Also, when I go to fill the system with refrigerant, do I need to add any PEG oil or just add refrigerant up to the specified capacity?