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  #1  
Old 03-09-2019, 05:25 PM
bradleyheathhays bradleyheathhays is offline
 
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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?
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Old 03-09-2019, 05:56 PM
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First things first
Usually when windows fog like that, the heater core is leaking hot antifreeze into the cabin air
You may or may not smell it
Look for wet carpet, etc

2nd
not sure about your car, but on my town car there is a control module that swings the heat/ defrost door open/ closed or middle. they break. to see if it's broken, change from floor to defrost and it will start clicking real bad. you can't mistake the clicking..

Sucky part about both repairs, the dash has to come part away from the windshield to get to the offending parts
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Old 04-01-2019, 11:19 PM
bradleyheathhays bradleyheathhays is offline
 
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Thanks for the reply dusty and sorry it's been so long since I dropped this. Life swept me away for a bit there.

Actually, my heater core went bad a few months back and it did just as you described...antifreeze smell and on the floor. Got the dash out and replaced it with new OEM so I'm sure that's ok.

I haven't noticed any kind of clicking like you describe when switching from floor to defrost so not sure if our cars have the same layout.

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 goes from medium cool up to barely cool and back down...keeps cycling like this about once a minute.

I'm ok with the air just coming out the vents. If I can get the a/c def fixed that's all I need really.

Any more ideas?
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Old 04-02-2019, 04:05 PM
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Have you checked the a/c charge?
could be as simple as a low Freon charge.
could be a blend door stuck ( not as simple to repair)
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Old 04-04-2019, 10:04 PM
bradleyheathhays bradleyheathhays is offline
 
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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.
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Old 04-07-2019, 03:58 AM
bradleyheathhays bradleyheathhays is offline
 
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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?
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Old 04-09-2019, 01:31 PM
bradleyheathhays bradleyheathhays is offline
 
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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?
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Old 04-09-2019, 07:50 PM
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If your not replacing any major components in the system there is no need to add oil. Most Freon cans have a little oil in them FYI.


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Old 04-10-2019, 03:57 PM
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If the Freon is totally gon, you really need to vacuum the system down
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