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#4112114 - 06/10/21 09:58 AM A/C starting strong then weakens.
ThomasTheGood Offline
n00b

Registered: 12/14/18
Posts: 12
Loc: USA
Hello,

I have a 2011 Crown Vic P71 Interceptor.

I had the A/C system worked on and recharged. When I start driving the a/c works fine and flows fine. After around 20-30 minutes the air will not blow as hard even on max and the only way to get air flow back is to put it on vent on max blower and eventually the air will come back and I can switch it to a/c again. What little air is coming out is cold there is just no pressure. I replaced the blower motor and blower motor resistor. Any help would be greatly appreciated.

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#4112122 - 06/10/21 11:11 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
AlleyG Offline
Climber

Registered: 04/28/14
Posts: 541
Loc: Raleigh, NC
I am in the same boat, though I'm not sure if it's the air blowing less or it's not as cold. Probably a little of both.

Ours takes a good hour or so for it to become "inadequate". My mechanic mentioned the low pressure switch at one point but he also said it was likely the compressor clutch getting weak, which can be replaced.

Al
_________________________
2004 CVPI - 85k miles
1997 T-Bird LX - 85k miles
1994 Supra Turbo - 107k miles
Previous Fords:
1988 T-Bird, 1995 T-Bird, 1996 Cougar

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#4112124 - 06/10/21 11:22 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
ThomasTheGood Offline
n00b

Registered: 12/14/18
Posts: 12
Loc: USA
When mine starts to weaken I can feel the cold through the vents but it's like the blender door started open then closed slowly over time. I know the HVAC controls work off of tubing so I wonder if it could be a leak.

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#4112130 - 06/10/21 11:30 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
AlleyG Offline
Climber

Registered: 04/28/14
Posts: 541
Loc: Raleigh, NC
I can feel cold also, but there's "cold" and then there's "COLD!". I think it's related to the compressor because even if the fan is blowing less on the higher settings, it should still be at least equivalent to the lowest setting on the fan, which is typically enough to maintain the temperature.

Al
_________________________
2004 CVPI - 85k miles
1997 T-Bird LX - 85k miles
1994 Supra Turbo - 107k miles
Previous Fords:
1988 T-Bird, 1995 T-Bird, 1996 Cougar

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#4112140 - 06/10/21 01:37 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
Old_Guy_Stu Offline

Over the Hill

Registered: 04/28/19
Posts: 2297
Loc: Cleveland, OH
Sounds like the evaporator is icing. You can counteract that by adjusting the cycling switch. Pull the plug and you'll see a small screw in there. Just a small tweak is all it needs. I think it's CW for less compressor time, but I could be wrong.
_________________________

1988 CVLX Formal Roof (Love Boat) POTM July 2019 & Aug 2020, 56K
E-code lights w/ relays, LEDs w/ switchbacks, 15x8 Ansen slots w/ 255/60 BFG's, Kenwood stereo, various hacks.
1988 CVLX (Destroyer) 1998-2001 driven to death 202K
1988 Squire (Chris Craft) 1996-1998 junkyard rescue driven to death 199K

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#4112142 - 06/10/21 01:51 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
ThomasTheGood Offline
n00b

Registered: 12/14/18
Posts: 12
Loc: USA
Cool Stu, I'll take a look when I get home, is that the switch on the compressor?


Edited by ThomasTheGood (06/10/21 01:53 PM)

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#4112146 - 06/10/21 02:01 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
Old_Guy_Stu Offline

Over the Hill

Registered: 04/28/19
Posts: 2297
Loc: Cleveland, OH
Not sure where it is on a late-model. Mine's on the low-pressure line (the larger one) near the drier.
_________________________

1988 CVLX Formal Roof (Love Boat) POTM July 2019 & Aug 2020, 56K
E-code lights w/ relays, LEDs w/ switchbacks, 15x8 Ansen slots w/ 255/60 BFG's, Kenwood stereo, various hacks.
1988 CVLX (Destroyer) 1998-2001 driven to death 202K
1988 Squire (Chris Craft) 1996-1998 junkyard rescue driven to death 199K

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#4112188 - 06/10/21 09:37 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
2008interceptor Offline
Over the Hill

Registered: 09/02/02
Posts: 3243
Loc: Pennsylvania
It could be the icing i've heard where people need to switch to norm from max/recirc or it freezes and stops cooling. Can happen to home units too if the fins get clogged with debris. Do you have any sort of a mold smell from the vents by chance?
_________________________
2008 Ford Crown Victoria Police Interceptor P71 with street appearance package.

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#4112214 - 06/11/21 08:31 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
AlleyG Offline
Climber

Registered: 04/28/14
Posts: 541
Loc: Raleigh, NC
Mine doesn't matter if it's on max or normal, it doesn't cool enough when it's acting up. Doesn't smell like mold either.

But Rob did mention the compressor could be freezing.

Al
_________________________
2004 CVPI - 85k miles
1997 T-Bird LX - 85k miles
1994 Supra Turbo - 107k miles
Previous Fords:
1988 T-Bird, 1995 T-Bird, 1996 Cougar

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#4112216 - 06/11/21 08:53 AM Re: A/C starting strong then weakens. [Re: Old_Guy_Stu]
Rootintootin Offline
Climber

Registered: 02/26/08
Posts: 638
Loc: North Carolina
Originally Posted By Old_Guy_Stu
Sounds like the evaporator is icing.


Uh, not the compressor, the evaporator.
_________________________
97 CVPI, 143K miles, small trans fluid leak from front seal area, water leaks to inside from evaporator housing and drivers side A pillar, cold weather glitch with wiper motor, headliner covering starting to flake off, tear in drivers seat bottom. Flickering, blinking radio display, What's next?

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#4112220 - 06/11/21 11:42 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
AlleyG Offline
Climber

Registered: 04/28/14
Posts: 541
Loc: Raleigh, NC
Can you visually see the icing?

Al
_________________________
2004 CVPI - 85k miles
1997 T-Bird LX - 85k miles
1994 Supra Turbo - 107k miles
Previous Fords:
1988 T-Bird, 1995 T-Bird, 1996 Cougar

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#4112222 - 06/11/21 12:01 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
Old_Guy_Stu Offline

Over the Hill

Registered: 04/28/19
Posts: 2297
Loc: Cleveland, OH
Not without tearing the dash apart. The evaporator is the first thing they put on the car and everything else is built around it. You might see some frost on the low-pressure lines, though. That's not a sure-fire indicator, but it's a pretty good one. If the frost is heavy (more than just a skin) then icing is a good bet.
_________________________

1988 CVLX Formal Roof (Love Boat) POTM July 2019 & Aug 2020, 56K
E-code lights w/ relays, LEDs w/ switchbacks, 15x8 Ansen slots w/ 255/60 BFG's, Kenwood stereo, various hacks.
1988 CVLX (Destroyer) 1998-2001 driven to death 202K
1988 Squire (Chris Craft) 1996-1998 junkyard rescue driven to death 199K

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#4112236 - 06/11/21 03:14 PM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7556
Loc: MA
If you pull the blower motor you can see the evaporator.
_________________________
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.

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#4112412 - 06/14/21 08:06 AM Re: A/C starting strong then weakens. [Re: ThomasTheGood]
AlleyG Offline
Climber

Registered: 04/28/14
Posts: 541
Loc: Raleigh, NC
Another symptom I forgot to mention: the defrost doesn't work in summer rainy conditions. It puts condensation on the outside of the window, which you have to keep the wipers on.

Normally turning up the temp to warm would eliminate that condensation, but it does nothing in this case.

Al
_________________________
2004 CVPI - 85k miles
1997 T-Bird LX - 85k miles
1994 Supra Turbo - 107k miles
Previous Fords:
1988 T-Bird, 1995 T-Bird, 1996 Cougar

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