#3339273 - 08/29/16 10:25 PM
Intermittent Cold In A/C
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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When I bought my car the A/C was not working at all. Had the system professionally charged and it failed in several locations. I changed all the hoses, condenser and recharged the system. It worked well but then started becoming this intermittent problem.
One minute it will be frosty cold cruising down the highway, then all of a sudden warm dog breath. I will be sitting idle ICE COLD and then go a few blocks and the mutt starts panting at me again.
Just to clear up I have searched this a lot, found not a lot that touches on this subject. And it isn't volume of air that is the problem because that stays constant, it is the temperature that fluctuates without me doing anything. I just had the system checked after 8 months of last opening the system and I haven't lost any refrigerant.
Any tips? Thoughts?
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3339385 - 08/29/16 11:38 PM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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n00b
Registered: 02/13/16
Posts: 14
Loc: Ky
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Assuming everything else is in good working order, especially the cooling fan I'm guessing you may be a bit undercharged.. I keep a thermometer in mine, I rebuilt my system myself and at 38 degree vent temps my system will start cycling.
Edited by _Clayton_ (08/29/16 11:40 PM)
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2001 CVPI
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#3339393 - 08/29/16 11:40 PM
Re: Intermittent Cold In A/C
[Re: _Clayton_]
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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Assuming everything else is in good working order, especially the cooling fan I'm guessing you may be a bit undercharged.. Nope. Checked with a snap-on A/C machine last week. Haven't lost any refrigerant in 8 months and it is exactly to spec. I am baffled...
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3339401 - 08/29/16 11:41 PM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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n00b
Registered: 02/13/16
Posts: 14
Loc: Ky
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What are your pressures and at what ambient temp? Oh and did it work fine before with the same readings?
Edited by _Clayton_ (08/29/16 11:42 PM)
_________________________
2001 CVPI
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#3339489 - 08/30/16 01:52 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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Climber
Registered: 07/09/09
Posts: 887
Loc: New England
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when its blowing hot, the compressor clutch is engaged?
low side pipes arent cold?
high side super hot?
_________________________
'03 Sport '07 Audi Q7 '87 Thunderbird 250,000 miles v6 blown head gasket  . I regret having it towed to the junk yard.
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#3339505 - 08/30/16 02:45 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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Over the Hill
Registered: 03/29/09
Posts: 4043
Loc: Columbus, OH
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When I bought my car the A/C was not working at all. Had the system professionally charged and it failed in several locations. I changed all the hoses, condenser and recharged the system. It worked well but then started becoming this intermittent problem.
One minute it will be frosty cold cruising down the highway, then all of a sudden warm dog breath. I will be sitting idle ICE COLD and then go a few blocks and the mutt starts panting at me again.
Just to clear up I have searched this a lot, found not a lot that touches on this subject. And it isn't volume of air that is the problem because that stays constant, it is the temperature that fluctuates without me doing anything. I just had the system checked after 8 months of last opening the system and I haven't lost any refrigerant.
Any tips? Thoughts? Okay, we need your car, model year, and whether or not the car is an EATC equipped vehicle. It sounds as if a blend door issue is at fault here. But beyond that we would be guessing unless we have the additional information.
_________________________
Stalag;___________Just for Rizzo I am posting this in my sig. Coolants 2001 Lincoln Town Car Cartier L Sent to graveyard
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#3339545 - 08/30/16 05:09 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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Whoops, my bad!
2001 CVPI CNG manual control...
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3340537 - 08/30/16 08:18 PM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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Climber
Registered: 07/09/09
Posts: 887
Loc: New England
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I was going to guess blend door if he said the low side pipe was freezing when it was blowing hot... but he didnt answer me yet! 
_________________________
'03 Sport '07 Audi Q7 '87 Thunderbird 250,000 miles v6 blown head gasket . I regret having it towed to the junk yard.
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#3340641 - 08/30/16 09:33 PM
Re: Intermittent Cold In A/C
[Re: bspurloc]
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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I was going to guess blend door if he said the low side pipe was freezing when it was blowing hot... but he didnt answer me yet! I'm gonna test it today and let you know!
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3340753 - 08/30/16 10:09 PM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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I know nothing
Posting Addict
Registered: 06/05/10
Posts: 19872
Loc: I can see Detroit from here!
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Blend door is out of the question for this issue. It won't switch back and forth, especially not with manual controls. I mean, unless its totally broken and the door is just flopping around, in which case he'd probably be hearing it, and it'd have no temperature control at all.
I think this is likely an issue of the compressor cycling on and off when it shouldn't. Usually this is a pressure issue, but as that has already been ruled out, it has to be for some other reason. The pressure switches, both low and high, can cause this but they rarely seem to fail on Fords.
And not to point out the obvious, but these cars do have a wide-open-throttle AC cut-out. When you go wide-open-throttle, the PCM de-energizes the AC compressor relay (actually listed as the WOT Cut-Out relay on the diagrams) which causes the compressor to turn off while WOT and for a few seconds after. It takes it a second or 10 to get real cold air blowing again when its hot outside.
_________________________
-Steve  2006 Audi A6 ~132k miles, stock. 1998 Mercury Grand Marquis LS HPP ~100k miles, slowly acquiring modifications. 1997 Town Car Cartier ~145k miles, Ported Plenum, Gutted Airbox, Contour E-fan Retrofit, Dual exhaust with Magnaflows, cats deleted, MSD Ignition, KYB Gas-A-Justs, P71 front bar, air ride reinstated, Projector retrofit, Caddy 4-note horn retrofit, Wood rim steering wheel retrofit, holistic weight reduction as the parts fall off.. 1996 Mercury Grand Marquis GS 117,485mi. R.I.P. 7/14/12
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#3340961 - 08/31/16 01:42 AM
Re: Intermittent Cold In A/C
[Re: BigMerc96]
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Climber
Registered: 07/09/09
Posts: 887
Loc: New England
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Blend door is out of the question for this issue. It won't switch back and forth, especially not with manual controls. I mean, unless its totally broken and the door is just flopping around, in which case he'd probably be hearing it, and it'd have no temperature control at all.
I think this is likely an issue of the compressor cycling on and off when it shouldn't. Usually this is a pressure issue, but as that has already been ruled out, it has to be for some other reason. The pressure switches, both low and high, can cause this but they rarely seem to fail on Fords.
And not to point out the obvious, but these cars do have a wide-open-throttle AC cut-out. When you go wide-open-throttle, the PCM de-energizes the AC compressor relay (actually listed as the WOT Cut-Out relay on the diagrams) which causes the compressor to turn off while WOT and for a few seconds after. It takes it a second or 10 to get real cold air blowing again when its hot outside. what about that AC Valve that is in the system? what is seen when that fails/sticks?
_________________________
'03 Sport '07 Audi Q7 '87 Thunderbird 250,000 miles v6 blown head gasket . I regret having it towed to the junk yard.
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#3341057 - 08/31/16 05:28 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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To add to all of this I will full throttle getting on the freeway wondering if the switch is odd, but the system will keep going then it will shut down...
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3341273 - 08/31/16 11:24 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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Over the Hill
Registered: 03/29/09
Posts: 4043
Loc: Columbus, OH
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At full throttle the AC is cut to apply all the power to the road. If you are not at full throttle and the AC blows warm and cool, some potential failure points are the AC switches that command the compressor off and on, or the blend doors malfunctioning, or a vacuum leak. You may have a combination of all three if you see this at any other condition than full throttle.
Edited by stalag (08/31/16 11:28 AM)
_________________________
Stalag;___________Just for Rizzo I am posting this in my sig. Coolants 2001 Lincoln Town Car Cartier L Sent to graveyard
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#3342986 - 09/01/16 03:25 PM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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n00b
Registered: 07/24/16
Posts: 35
Loc: California
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Yes the condition is present at all speeds and throttle inputs. I will have to check the A/C switches, I hope I will not have to replace the blend door and I will smoke test the system to check for vacuum leaks. Anyone know a procedure for checking A/C switches?
_________________________
--2001 Ford Corwn Victoria P71 CNG--
True dual exhaust w/ H pipe and magnaflows, replacing all the wear parts 1 by 1. To come posi rear, 18" steel police style wheels, sound system.
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#3346578 - 09/04/16 02:59 AM
Re: Intermittent Cold In A/C
[Re: ECTOCNGP71]
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Climber
Registered: 07/09/09
Posts: 887
Loc: New England
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Still havent heard back if the low side pipe is freezing when its blowing heat.
Answering that question will eliminate the blend door as a problem and other issues.
I mean you mentioned the pressures were right but didnt mention the pressures seen, and was that when it was blowing heat.
I mean all the testing should be done when its blowing heat, the low side pipe not being cold would explain why its not blowing cold air. Low side would be fill valve near he firewall not the one near radiator.
I am assuming blowing heat means its not cold not like the heater is on.
_________________________
'03 Sport '07 Audi Q7 '87 Thunderbird 250,000 miles v6 blown head gasket . I regret having it towed to the junk yard.
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