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#4408231 - 05/18/17 08:14 PM 2003 Town Car a/c short cycles and is weak
Canadastang Offline


Registered: 12/08/15
Posts: 261
Loc: Ontario Canada
My new to me Town Car's a/c never worked, so after changing the rotted out accumulator and having the system vacuumed and recharged, it's finally working - but - it's short cycling - the compressor will run for about 10 seconds, then shut off for about 10 seconds, then back on. the a/c does blow cold when the compressor is engaged, but I measured 66*F vent temp with outside temp of 80F - so they a/c is weak, but perhaps it's because the compressor's only running 50% of the time.

I had the shop re-check the charge yesterday, and it was low, so they vacuumed it and recharged it again and found a very small leak on the suction line leaving the accumulator (where the rubber hose is crimped into the fitting). In about a month it's lost about a pound of refrigerant.
Anyways, the a/c still behaves the same, even immediately after a full charge.

IIRC when the gauges were hooked up after recharging, the low side was between 40-60 and the high side 150-170 - ambient temp was about 75f, a/c was on max with windows open.

From what I've read, the high side seems low and the low side seems a bit high.

I took some temp measurements tonight with my IR gun:

again, AC on max, windows down, ambient temp of 80F

At evap lines:

Suction - 73F
Liquid - 103F - in front of orifice
Liquid - 76F at rear of orifice (cabin side)

Accumulator temp: 66F

Center vent temp: 65F

Obviously I'll eventually have to replace the leaky hose, but what could be causing the low reading on the high side? Clogged orifice? Bad compressor? The condenser fins are clean and clear of debris. Car only has 95000km's (60000 miles~)

a/c systems are kind of foreign to me, hopefully someone can point me in the right direction



Edited by Canadastang (05/18/17 08:15 PM)

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#4408244 - 05/18/17 08:29 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Dylan1303 Offline


Registered: 10/14/15
Posts: 180
Loc: Washington
I had a similar problem today. Wifes 09 fusion, today was the first time we tried the ac and ofcourse it blew hot air. So i put in 3, 12 ounce cans of r134a and the compressor would kick on and off every 3 seconds. So i did some googleing and found out i over filled the system. Bleed some out and it started working perfect. Push on the valve until liquid comes out. And hopefully it will fix yours like it did mine. If you overfilled it.
_________________________
12 chevy cruze 1.4t 6spd penz euro 0w40
09 ford fusion 2.3l auto royal purple 5w20

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#4408249 - 05/18/17 08:37 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Dylan1303]
Canadastang Offline


Registered: 12/08/15
Posts: 261
Loc: Ontario Canada
Highly doubt it was overfilled. I watched the guy vacuum the system out and refill it with a snap-on a/c service machine, he drained the system entirely and entered the correct weight of refrigerant and let the machine do its work.

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#4408250 - 05/18/17 08:37 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Colt45ws Offline


Registered: 08/15/06
Posts: 9651
Loc: Central Washington
The computer ultimately controls the A/C cycling. The signal from the cilmate control requesting A/C first passes through the low pressure safety switch on the accumulator then goes to the PCM.
When the PCM sees this, it looks at the high side pressure sensor and the evaporator temperature sensor and cycles the compressor based on those two (also adjusts engine fan speed based on high side pressure.)
The compressor can also cycle from the low pressure switch.

So, it would be easier if you had access to some way of looking at what the PCM is seeing. If you have a bluetooth OBD2 reader and a Laptop, a program called Forscan can do that.

If it thinks the evaporator is getting too cold (risk of freezing) then it will cycle the compressor off. This could be caused by a plugged evaporator. Since these cars do not have a cabin filter, thats a possibility.
If the pressure on the high side is too high it will cycle it off as well. Since your pressures are ok, it would make me think that sensor might be bad, but again would be best to see what the computer is seeing.
_________________________
-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2

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#4408252 - 05/18/17 08:40 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Colt45ws]
Canadastang Offline


Registered: 12/08/15
Posts: 261
Loc: Ontario Canada
Yeah, I wish I could see what the PCM is doing, I just bougth an Autel 519 and tried it out, but it can't check HVAC data.

Forscan sure would be handy, otherwise I may have to bring it back in to get it scanned.

I doubt that the evaporator is actually freezing over since it will short cycle immediately on the first start of the day, but an evap sensor issue sure sounds possible.


Edited by Canadastang (05/18/17 08:43 PM)

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#4408261 - 05/18/17 08:52 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Colt45ws Offline


Registered: 08/15/06
Posts: 9651
Loc: Central Washington
You could ohm out the sensor and see that way.

The sensor is on the A/C box near the heater hoses.
Its telling that they deleted this sensor for 05 and went back to relying on the low pressure switch to keep the evaporator from freezing.
03-04 only thing.


Edited by Colt45ws (05/18/17 08:53 PM)
_________________________
-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2

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#4408262 - 05/18/17 08:53 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
SilverFusion2010 Offline


Registered: 06/29/11
Posts: 1665
Loc: Crawfordville FL
Put a set of manifold gauges on it and see if either high or low are getting out of range. If both seem reasonable when the compressor is on, then I would start checking sensors. Alternatively you could run a 12v jumper to the line that activates the clutch (it's an electromagnet) and add a toggle switch lol.


No don't do that lol. Might be useful for testing purposes though.

I would look for a clog on the low side close to the compressor. Either clogged or the compressor seals are leaky with the pressures you posted.

If it was mine, I'd open the system, take it apart blow cleaned and dried air through all the lines. Have a look at the orifice filter, replace any damaged o-rings and give them all just a dab of silicone grease before putting it all back together. Take it to your AC shop and ask them to pull a vacuum on it and hold it for as long as possible, at least an hour, maybe a bit longer, then refill with correct oil and refrigerant charge. Test with manifold gauges hooked up and see what you get.

Good luck



Edited by SilverFusion2010 (05/18/17 09:04 PM)
_________________________
2010 Ford Fusion SE 3.0L V6, 178k miles M1 HM 10w-30

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#4408311 - 05/18/17 10:20 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Chris142 Offline


Registered: 06/05/03
Posts: 16844
Loc: Deplorable in apple valley, ca
Replace the low pressure cycling switch.
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87 F250 traveler 15w40
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#4408996 - 05/19/17 07:12 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Colt45ws]
Canadastang Offline


Registered: 12/08/15
Posts: 261
Loc: Ontario Canada
Originally Posted By: Colt45ws
You could ohm out the sensor and see that way.

The sensor is on the A/C box near the heater hoses.
Its telling that they deleted this sensor for 05 and went back to relying on the low pressure switch to keep the evaporator from freezing.
03-04 only thing.


I tested the evap sensor at about 24k ohms. Ambient temp was about 75F, and with the car's black leather interior, evap temps could have been about 85F, so, it seems okay.

Low pressure switch tests fine.

I ordered a usb dongle to run Forscan, should be here on Tuesday.

On the way home today, I stopped by the local pick n pull and grabbed an a/c clutch electrical connector to put battery voltage directly on the clutch to see how it behaves (for testing purposes only of course, although I could always wire a thermostat in line LOL).

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#4414093 - 05/25/17 01:49 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Canadastang Offline


Registered: 12/08/15
Posts: 261
Loc: Ontario Canada
Colt45ws was right on the money!

Although the evap temp sensor tested okay on my multimeter, it was providing erratic readings to the ecu.

I checked it again with my multimeter and lo and behold, the resistance bounces all over the place when the sensor is moved in the slightest.

Stopped by a pick n pull and grabbed a new sensor - now the a/c is ice cold and doesn't short cycle.

On max a/c at idle I'm getting 39*F out of the center vents.

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#4414841 - 05/26/17 11:35 AM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Colt45ws Offline


Registered: 08/15/06
Posts: 9651
Loc: Central Washington
Sounds like you fixed it! Awesome!
_________________________
-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2

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#4565008 - 11/05/17 03:16 PM Re: 2003 Town Car a/c short cycles and is weak [Re: Canadastang]
Colt45ws Offline


Registered: 08/15/06
Posts: 9651
Loc: Central Washington
I know this is a few months after the fact, but I thought I would add onto this with some useful info in case another person with a 03-04 panther has these sorts of issues.
My 03 was short cycling it in defrost. I know it is cold but it would run for maybe 1/2 a second and kick out. Annoying to me anyways. First thing I did was just swap this sensor with another I have. Didnt really change it.
But then I stuck a 22k resistor into the connector for it, sending it a false signal that its like 80F or something.
That seems to work perfectly. Doesnt seem to be checking if the input makes sense at all, so its just letting the compressor run. It runs until the low pressure sensor trips, basically returning it to Pre-03, Post-04 function.
Supposedly the sensor was added to prevent evaporator freezing, but obviously it was an edge case since it was removed again. Thats what the low pressure sensor is for and I never had that problem on my 02 without the sensor.
Im gonna run it far awhile and see how it goes. If its okay, Ill snip the connector off and solder the resistor in line permanent.
_________________________
-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2

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