AC Help Please

PC PaiN

New Member
Jul 11, 2007
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I had my A/C Clutch and Coil replaced under extended warranty before it ran out on my 01 Bullitt about a month ago. About 5 days ago or so the A/C would randomly stop blowing cold and blow only hot air. Then it would start blowing cold again. Well the other day I left work and it was blowing cold air, while on the way home it stopped blowing cold air and hasn't since.

I went ahead and replaced the low pressure switch since it's cheap but it didn't fix my issue. I have 12 volts coming out of the solid wire on the switch, but no voltage coming out of the blue wire with a tracer (not sure of exact color)

Now another thing I have noticed since this started is that when you turn the temp knob it pulls itself all the way over to heat after it reaches about halfway, this gets worse based on the blower speed. It fights you going back to the cold setting.

Anyone have any tips? The clutch is not engaging on the compressor, but everything seems to spin freely
 
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Hard to say what the cause is. I would definately take it back to the ford dealer and see if they are willing to do some warrenty work since it just ended so recently. They are human and sometimes understanding. Also, it could be their work that caused the problems. What you describe 'could' be low refridgerant which could be related to them pushing the lines around during the previous work on the clutch.
 
Kinda sounds like the blend door to me too. BTW , do you have headers ? I had a similar issue this past week and it turns out my passenger side header slowly burnt a hole in one of my AC lines. A tech and myself walked out to my car and he pulled off the test port cap and put his pen in it and no refrigerant came out and got to looking and the lower AC line was laying on the header. Had to skip Shelby Fest because I had no AC.:(
 
Can you guys tell me how to check the blend door and what it is? I would rather not go back to the dealer as I had trouble getting it fixed and some leaks at the same time because I was 29 miles away from my warranty going out. Also would the blend door explain the ac clutch not ingauging? Does it make the system think it's on heat?
 
Umm, you really need to hook up a set of gauges to see if the AC system is working properly. I beleive the blend door that others are talking about is the door behind the dash that controls how much airflow goes through the heater core. You mentioned a problem with the temperature knob acting funny, so that would point to that door. It could be that the AC is working, but the heater is warming the air back up before it is blown out the vents.

However, you said the AC compressor isn't running, so there is definately a problem there unrelated to the temperatur knob/blend door.
 
yea the clutch is not engaging and it is brand new along with the coil. Does anyone know if the two wires running to the low pressure switch should both have voltage with the a/c on? Jumping the two does not cause the clutch to engage and I have no voltage coming out of one of the wires.
 
I don't have a wiring diagram infront of me, but I would think there should be voltage on one side of the low pressure switch. Then, the switch closes and sends the voltage to the other side (to the coil).
You said the compressor does not engage when you short the low pressure switch? Pull off the wire going to the compressor and put your voltmeter on these 2 wires at the same time. There should be zero voltage with the AC off. Turn the AC on and short the low pressure switch and you should get a a voltage to these wires. If there is voltage, but the compressor still doesn't run when the voltage is present, then the problem is the compressor/coil assembly. If there is not voltage, the problem is another switch or the wiring. There is a high pressure switch too.
 
If the compressor is not being energized, AC gauges will not be of much use. Pressure readings must be made while the system is operating.
I don't know if there is an electrical linkage to the blend door. But, if you select the "defrost" position, the compressor should come on regardless of the temperature setting.

According to the 2001 wiring diagram I have, The compressor clutch solenoid is driven by a relay in the (dreaded) CCRM. That relay is driven by the powertrain computer (PCM). The pressure switches are wired to the PCM.

Assuming the compressor does NOT energize with defrost selected, the first thing to check is if voltage is being applied to the clutch coil. Pull off the connector and connect your voltmeter between the 2 connector pins. If voltage is present, you have an open clutch coil or bad compressor clutch (even new ones can be defective). With the connector removed, you can also measure across the clutch coil terminals with your meter's resistance scale. I don't know the precise resistance, but it should definitely be less than 20 ohms.

If ~12V cannot be measured between the clutch coil connector terminal pins with the engine running and the selector in the defrost position, then the cause could be within the CCRM, PCM, or wiring. To me, that the clutch was recently replaced makes it the first thing I would suspect.

What were the symptoms that led to the clutch being replaced under warranty? Perhaps it was not the clutch that was the cause of the original problem.
 
Well I just started the car since I haven't driven it in a few days and the ac works now I'm really confused. I turned the car off and back on and it seemed like the clutch wasn't going to engage so I switched to defrost and back over to ac and it worked. Now when I turned the car off it sounded like something was hissing but it went away after the car was off for a few seconds. I'm at a loss right now on where to look next
 
This could be as simple as a loose connector to the heater/AC selector switch, or an intermittent or worn contact within the switch. In the AC position, you could check if applying a slight twisting force to the knob (but without actually moving it from the "AC" setting, causes the clutch to disengage. You might also try lightly tapping on the knob with the rubber-covered handle of a screwdriver.

When the AC is operating, the compressor increases the pressure in some of the refrigerant lines, and reduces the pressure in others. This differential pressure is miantained because the refrigerant flow path between high and low pressure portions of the syayem is restricted. Once the compressor turns off, the systsm pressure gradually equalizes. High pressure refigerant flows to the low pressure side. This equalization process can take 10-30 seconds and may explain the "hissing" you hear. It should sound something like the sound water makes flowing through a valve that is only partially open.