Problem w/ intermittent defrost a/c - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
Ford Crown Victoria | Mercury Marauder | Grand Marquis | P71 Forum for discussion of the Ford Crown Victoria, Mercury Marauder, Mercury Grand Marquis and P71.

 2Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 16 (permalink) Old 03-09-19, 03:16 PM Thread Starter
Registered User
 
Join Date: Aug 2013
Posts: 60
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?

bradleyheathha is offline  
Sponsored Links
Advertisement
 
post #2 of 16 (permalink) Old 03-09-19, 03:31 PM
Administrator
 
Join Date: Sep 2006
Location: Arkansas
Posts: 8,120
Re: Problem w/ intermittent defrost a/c

Moved to the Crown Vic section.
jwko is offline  
post #3 of 16 (permalink) Old 03-09-19, 05:47 PM
Moderators
 
Join Date: Apr 2016
Location: Naples, Fl
Posts: 729
Re: Problem w/ intermittent defrost a/c

How well does your ac work? Does it cut out at only wide open throttle or randomly?


Sent from my iPhone using Tapatalk

07 Gt Tungsten Grey
Roush (Airaid) Cai, GT500 Tb with BlowByRacing Adaptor Plate, UPR O/r X Pipe, M80's, Pypes Muffler Delete Axle Back, Sr Performance Adjustable Motor Mounts and Steeda Tri Ax Short Throw Shifter

02 Gt Mineral Grey
Steeda Sport Springs, 3.73s, Pro5.0 Short Shifter, Pypes O/r X Pipe, full 2.5 inch exhaust with M80's, 75mm Tb and C&L Plenum

87 Mercury Grand Marquis
85ltdcrownvic is offline  
Sponsored Links
Advertisement
 
post #4 of 16 (permalink) Old 03-09-19, 06:57 PM
Dazed and Confused
 
CatSkinner's Avatar
 
Join Date: May 2012
Location: Upstate New York
Posts: 7,571
Re: Problem w/ intermittent defrost a/c

Sounds like your blend door isn't working, at least not properly. The fan working intermittently sounds more like a safety, your evaporator coil may be icing up.
Bert likes this.

Ever notice that there's so many high performance parts available for GM products?

Did you ever think that maybe they NEED them?
CatSkinner is offline  
post #5 of 16 (permalink) Old 03-31-19, 10:30 PM Thread Starter
Registered User
 
Join Date: Aug 2013
Posts: 60
Re: Problem w/ intermittent defrost a/c

Thanks for the help and sorry it's been so long since posting this. Still having the same problem.


A/C works sort of intermittently like the defrost. It goes from medium cool air to slightly cool air, back and forth about once every minute or two. Doesn't seem to be effected by the throttle but I'll try to remember to test it out.


CatSkinner actually the fan works ok, it's the temp (a/c) that goes up and down, or the defrost that seems intermittent. But the fan, air movement, is ok.


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?


And if my evap coil is icing over how could I test that out. I don't even know where the dang thing is. The cycling of the cool to slightly cool air and back again happens like I was saying about once every minute or two, so without knowing much about this I'd think that wouldn't be enough time for the coil to ice up and then thaw out. But that just my amateur 2 cents.
bradleyheathha is offline  
post #6 of 16 (permalink) Old 04-01-19, 12:10 PM
Moderators
 
Join Date: Apr 2016
Location: Naples, Fl
Posts: 729
Problem w/ intermittent defrost a/c

The evaporator is in the dash not accesable but youll know its icing over when the ac isnt sweating as much as before and the compressor would short cycle. There is a high pressure cutoff switch on the drier (its a black cylinder on the passenger side near the firewall in the engine bay) but I doubt the switch is the culprit. At this point your best bet is to put manifold gauges on it and see where the pressure is on the low and high side.


Sent from my iPhone using Tapatalk

07 Gt Tungsten Grey
Roush (Airaid) Cai, GT500 Tb with BlowByRacing Adaptor Plate, UPR O/r X Pipe, M80's, Pypes Muffler Delete Axle Back, Sr Performance Adjustable Motor Mounts and Steeda Tri Ax Short Throw Shifter

02 Gt Mineral Grey
Steeda Sport Springs, 3.73s, Pro5.0 Short Shifter, Pypes O/r X Pipe, full 2.5 inch exhaust with M80's, 75mm Tb and C&L Plenum

87 Mercury Grand Marquis
85ltdcrownvic is offline  
post #7 of 16 (permalink) Old 04-01-19, 05:20 PM
Administrator
 
Join Date: Sep 2006
Location: Arkansas
Posts: 8,120
Re: Problem w/ intermittent defrost a/c

Quote:
Originally Posted by 85ltdcrownvic View Post
The evaporator is in the dash not accesable but youll know its icing over when the ac isnt sweating as much as before and the compressor would short cycle. There is a high pressure cutoff switch on the drier (its a black cylinder on the passenger side near the firewall in the engine bay) but I doubt the switch is the culprit. At this point your best bet is to put manifold gauges on it and see where the pressure is on the low and high side.
That is the low pressure switch on the receiver/drier
jwko is offline  
post #8 of 16 (permalink) Old 04-02-19, 06:34 AM
Moderators
 
Join Date: Apr 2016
Location: Naples, Fl
Posts: 729
Re: Problem w/ intermittent defrost a/c

Quote:
Originally Posted by jwko View Post
That is the low pressure switch on the receiver/drier


Hmm Im sure youre right. Thanks for correcting that.


Sent from my iPhone using Tapatalk

07 Gt Tungsten Grey
Roush (Airaid) Cai, GT500 Tb with BlowByRacing Adaptor Plate, UPR O/r X Pipe, M80's, Pypes Muffler Delete Axle Back, Sr Performance Adjustable Motor Mounts and Steeda Tri Ax Short Throw Shifter

02 Gt Mineral Grey
Steeda Sport Springs, 3.73s, Pro5.0 Short Shifter, Pypes O/r X Pipe, full 2.5 inch exhaust with M80's, 75mm Tb and C&L Plenum

87 Mercury Grand Marquis
85ltdcrownvic is offline  
post #9 of 16 (permalink) Old 04-04-19, 08:19 PM Thread Starter
Registered User
 
Join Date: Aug 2013
Posts: 60
Re: Problem w/ intermittent defrost a/c

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.
bradleyheathha is offline  
post #10 of 16 (permalink) Old 04-05-19, 07:22 AM
Moderators
 
Join Date: Jul 2011
Posts: 1,022
Re: Problem w/ intermittent defrost a/c

Try the dye first. Any leak will then be easily detectable with ultraviolet light. The system probably has some already installed from the factory, but add some to be sure (Gauges will only indicate a leak, but not where). You can then fix the leak before losing expensive refrigerant.
Bajarider is offline  
Sponsored Links
Advertisement
 
Reply

  Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > Ford Cars and PAG Vehicles > Ford Crown Victoria | Mercury Marauder | Grand Marquis | P71


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 



Similar Threads
Thread Thread Starter Forum Replies Last Post
A/C problem: cooled air won't come out after long driving liolau Ford Taurus | Mercury Sable | Ford Taurus SHO | 1986-2007 12 09-16-09 04:11 PM
2004 Stalls when Defrost/ A/C is turned on Dhorwood Ford Escape | C-MAX | Mercury Mariner Forum 5 05-18-09 05:33 PM
2001 Mercury Sable A/C problem tombest44 Ford Taurus | Mercury Sable | Ford Taurus SHO | 1986-2007 4 05-10-09 04:57 PM
94 850 intermittent starting problem; nothing's helping! Sam Volvo 10 12-27-05 08:01 PM
Intermittent Light problem Pepe Jaguar 6 12-25-05 08:01 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome