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High Freon Pressure in 99 Ford Escort
05-08-2010, 01:42 PM
My A/C just stopped blowing cold air the other day, when I turn the A/C on the fan just blows air (as if it was just the regular vent) but no cold air. It started to work briefly a day later, I tested the pressure today and it was around 90 PSI which according to the chart was dangerously high. What would cause that and what would the solution be?
Thanks in advance for your help.
05-08-2010, 02:53 PM
I just went out and checked mine and it's at 85PSI. The 'safe range' is where it should be when the A/C is running. When the compressor kicks in it'll draw that pressure down.
05-08-2010, 03:39 PM
I had my A/C running on full, I had the "Type" knob on Max A/C and the "Speed" on full. I left it running around for around 5 minutes and it was still high and still no air. It looked like the clamp had a minor leak. Could that be the cause?
05-08-2010, 04:55 PM
When the engine has been off for at least 5 minutes, low side pressure and high side pressure should equalize. Pressure should be close to ambient temperature... 70 degrees outside, 70psi.
When the compressor turns on, high side pressure should rise to around 180psi. Low side pressure should drop to approximately 22psi, then the compressor should shut off. When low side pressure rises to around 42psi, the compressor should turn on again and the cycle starts over.
With a clutch cycling system such as yours, compressor "ON time", "OFF time", total cycle time, and high side pressure vary greatly according to ambient temperature, humidity and engine cooling system performance however, low side pressure should always remain in the 22psi to 42psi range when the A/C is running. With clutch cycling systems, the days of adding a can of refrigerant are over. The system will not operate properly unless it has the correct amount, (within a couple of ounces) of refrigerant. The ONLY way to know how much refrigerant is in the system is to drain, evacuate, and recharge it with the proper amount of refrigerant and oil.
05-08-2010, 07:49 PM
In the 3rd generation Escorts - '97 onwards - the relay for the A/C clutch coil was hidden away inside a module called the Constant Control Relay Module (CCRM), where it's mounted on a printed circuit board (PCB). One of the solder connections is prone to fail, leading to either no A/C, or intermittent operation.
Replacement CCRMs are expensive but many people have had success in repairing them, which isn't difficult if you're handy with a soldering iron or know somebody who is.
It's common though for a replacement CCRM to be fitted but the A/C still fails to operate, but it's easy to determine if your CCRM is faulty by checking the voltages at three pins on the CCRM, using either a multimeter or a 12 volt test lamp.
There are two different types of CCRM:
In one type, pin 22 will normally sit at 0V, and then when the A/C is switched on, the voltage will rise to 12V, at which time 12V will also appear on pin 23 and the A/C clutch should engage.
In the other type, pin 22 will normally sit at 12V, and then when the A/C is switched on, the voltage will fall to 0V, at which time 12V will appear on pin 23 and the A/C clutch should engage.
Regardless of which type you have, you're looking to see if the voltage at pin 22 changes when the A/C is switched on - if it does change but 12V does not appear on pin 23 then check for 12V on pin 21 - if you have 12V on pin 21 but not on pin 23, then the CCRM is faulty and should be repaired or replaced.
On the other hand, if the voltage at pin 22 changes when the A/C is switched on and 12V does indeed appear on pin 23, then that indicates that the CCRM is working fine, so your problem lies after that point - probably in the wiring to the A/C compressor clutch coil, or its ground connection.
If you find that the voltage at pin 22 does not change then the problem is prior to that point and therefore there would no reason to suspect the CCRM. Let me know if you don't follow any of that.
If you do determine that the CCRM is faulty, there's a photo guide to repairing the PCB here (http://www.feoa.net/modules.php?name=Forums&file=viewtopic&t=40417&postdays=0&postorder=asc&start=0), and you might also want to have a read of this thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=504830).
05-08-2010, 07:58 PM
Simple things first. Check your fuses.
If you have the know how, you can use jumpers at the fuse box to get power to the compressor and see if it will run.
The CCRM issue as described above is a likely scenario, but do some troubleshooting before you start changing parts. Most likely you WILL NOT need a new compressor... but that is not out of the question either.
05-09-2010, 09:47 AM
I found it faster and easier to just wire in an external relay- wired in parallel to the CCRM- use the inputs to draw in the relay coil and output the 12v to the compressor-- just like the CCRM does.
05-10-2010, 11:53 PM
Have you checked for a blown fuse? If the AC doesn't operate the system could need freon, you could have an open on the wiring circuit, the selector switch could be bad or the CCRM is faulty. You could have a restricted evaporative core orifice, also. The expansion valve under the hood could be restricted.
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