Chrysler Repair: AC Low Pressure Switch: 01 minivan, dodge grand caravan, clutch assembly

Question
QUESTION: We have a 2001 Dodge Grand Caravan, 3.3L V-6, flex fuel W/O rear air conditioning.  The air conditioning stopped working and we noted that the compressor was not engaging.  As the car has 127,000 miles, I decided to replace the compressor and clutch assembly along with a receiver/dryer.  After replacing these parts with new ones, the system was pressurized and showed no signs of leaks.  We then had it evacuated with a vacuum pump and started adding freon.  After adding 10 ounces of freon, we started the car and tried to turn on the airconditioner, but the compressor clutch would not engage.  I have checked the AC clutch fuse and relay and found them both functional.  I would like to disconnect wires from the AC Low Pressure Switch and short them to make sure the switch is not the problem.  However, I can not find the switch.  It is not threaded into the expansion valve as shown on the "autorepair.about.com" web site.  Can you help me locate this switch and do you have other suggestions I should try.

Thank you kindly for your help.

Bill

ANSWER: Hi Bill,
I believe that you are not getting 'action' from the compressor because you have not put in sufficient refrigerant. The system capacity is 34 oz. so the pressure so far is too low to allow the compressor to be activated. The pressure transucer you are looking for is near the right wiper module drain tube and the right strut tower and the high pressure service port. The plug has 4 pins/3 wires:dark blue/dark green (sensor gground), pink/yellow (sensor supply voltage), light blue/brown (sensor signal). The normal pressure to allow clutch activation would be a voltage reading of 0.451 to 4.519V between the light blue/brown and the dark blue/dark green wires. The pink/yellow should have 5.0V on it. You could probe through the insulation of the wires to see if you have sufficient refrigerant at this point.
Roland

---------- FOLLOW-UP ----------

QUESTION: Hi Roland,
I looked at the car again and the switch location you described is in the high pressure line (line from receiver/dryer to expansion plate).  The wire colors match what you noted and the input voltage checks at 4.9.  Could this be a combination high/low pressure switch?

Thanks for your time.

Bill

Answer
Hi Bill,
It is the one pressure switch both high and low and I believe that you have the pressure too high. If the supply wire (pink/yellow) shows 5V then the normal sensor reading should be below 4.52V as I described earlier. That is probably why you can't get 'action' from the clutch.
Roland