My son's Durango AC clutch will not pull in. It has continuity through the windings but no power to them. The fuses and relays all check out. I am looking fo a wiring diagram so that I might be able to locate where the power to the clutch is being interrupted. I found a trouble shooting guide on this forum, which was a pdf of a section from a service manual, and it referenced wiring diagrams in the text when giving troubleshooting tips but that section was not included. Does anyone have any suggestion?

 

Welcome to the site. I will move this thread to the first generation Durango section,
FF

 

Most of the time it is usually low freon in the system that will make the clutch not get power. Check that first. After you check that, check the low pressure and high pressure switches for power. You can unplug those one at a time and cross the connector to see if your clutch will engage. If you cross the low pressure connector and the clutch engages, you are low on freon. Power has to go through both of these switches in order for your clutch to engage. Too low of freon causes low pressure switch to go to an open position causing no power to clutch. Too high of pressure will cause the high pressure switch to go to open position causing no power to clutch.

Here is information on the R134A System. I know it is long winded but it might help you. This is copied from a site that explains about R134A Systems.

For vehicles currently running with freon R-134a only
Outside-----low side-------High side------Center vent temp
60 F -----28-38 psi----130-190 psi ----44-46 F
70 F ------30-40 psi ---190-220 psi ----44-48 F
80 F ------30-40 psi ---190-220 psi ----43-48 F
90 F ------35-40 psi ---190-225 psi ----44-50 F
100 F -----40-50 psi ---200-250 psi ----52-60 F
110 F -----50-60 psi ---250-300 psi ----68-74 F
120 F -----55-65 psi ---320-350 psi ----70-75 F
_
You can also use this good rule of thumb with R134a, run fan on High with all windows open and engine at 1500 rpm. High side pressure in PSI should be about 2.2 to 2.5 times outside air temperature in degrees F. Example if it's 90 degrees F, high side should be no higher than 225PSI


Here is a useful trouble shooting chart for systems currently running on freon R-134a

Trouble shooting

Low Compressor Discharge Pressure
1. Leak in system 2. Defective expansion valve 3. Suction valve closed 4. Freon shortage 5. Plugged receiver drier 6. Compressor suction valve leaking 7. Bad reed valves in compressor

Repair
1. Repair leak in system 2. Replace valve 3. Open valve 4. Add freon 5. Replace drier 6. Replace valve 7. Replace reed valves

High Compressor Discharge Pressure
1. Air in system 2. Clogged condenser 3. Discharge valve closed 4. Overcharged system 5. Insufficient condenser air 6. Loose fan belt 7. Condenser not centered on fan or too far from radiator

Repair
1. Recharge system 2. Clean condenser 3. Open valve 4. Remove some refrigerant 5. Install large fan 6. Tighten fan belt 7. Center and check distance

Low Suction Pressure
1. Refrigerant shortage 2. Worn compressor piston 3. Compressor head gasket leaking 4. Kinked or flattened hose 5. Compressor suction valve leaking 6. Moisture in system 7. Trash in expansion valve or screen

Repair
1. Add refrigerant 2. Replace compressor 3. Replace head gasket 4. Replace hose 5. Change valve plate 6. Replace drier 7. Replace drier

High Suction Pressure
1. Loose expansion valve 2. Overcharged system 3. Expansion valve stuck open 4. Compressor reed valves 5. Leaking head gasket on compressor

Repair
1. Tighten valve 2. Remove some refrigerant 3. Replace expansion valve 4. Replace reed valves 5. Replace head gasket

Compressor Not Working
1. Broken belt 2. Broken clutch wire or no 12v power 3. Broken compressor piston 4. Bad thermostat 5. Bad clutch coil 6. Low Refrigerant - low pressure switch has cut off clutch power

Repair
1. Replace belt 2. Repair wire or check for power 3. Replace compressor 4. Replace thermostat 5. Replace clutch coil 6. Add refrigerant

Evaporator Not Cooling
1. Frozen coil, switch set too high 2. Drive belt slipping 3. Hot air leaks into car 4. Plugged receiver drier 5. Capillary tube broken 6. Shortage of refrigerant 7. High head pressure 8. Low suction pressure 9. High suction pressure 10. Defective expansion valve 11. Frozen expansion valve

Repair
1. Turn thermostat switch back 2. Tighten belt 3. Check for holes or open vents4. Replace drier 5. Replace expansion valve 6. Add refrigerant 7. See problem #2 8. See problem #3 9. See problem #4 10. Replace expansion valve 11. Evacuate and replace drier

Frozen Evaporator Coil
1. Faulty thermostat 2. Thermostat not set properly 3. Insufficient evaporator air

Repair
1. Replace thermostat 2. Set to driving condition 3. Check for excessive duct hose length, kink or bend.

If you can't get your a/c to turn on then use this chart to determine if you are low on freon. Remember that this is a general char and will very for different makes and model cars and refrigeration units

Temperature -------------------134a Pressure(Psig)
-60.0----------------------------------21.6*
-55.0 -----------------------------------20.1*
-50.0 ---------------------------------- 18.5*
-45.0 ----------------------------------- 16.7*
-40.0 ----------------------------------- 14.6*
-35.0 ----------------------------------- 12.3*
-30.0 ----------------------------------- 9.7*
-25.0 ------------------------------------ 6.7*
-20.0 ------------------------------------ 3.5*
-15.0 ------------------------------------ 0.1
-10.0 ----------------------------------- 2.0
-5.0-----------------------------------------4.2
0----- ------------------------------------- 6.5
5.0 ---------------------------------------- 9.2
10.0 ------------------------------------- 12.0
15.0--------------------------------------15.1
20.0 --------------------------------------18.5
25.0 ------------------------------------- 22.2
30.0 --------------------------------------26.1
35.0 --------------------------------------30.4
40.0---------------------------------------35.1
45.0---------------------------------------40.1
50.0 --------------------------------------45.5
55.0---------------------------------------51.2
60.0--------------------------------------- 57.4
65.0----------------------------------------64.1
70.0--------------------------------------- 71.1
75.0 ---------------------------------------78.7
80.0--------------------------------------- 86.7
85.0--------------------------------------- 95.3
90.0 ------------------------------------ 104.3
95.0--------------------------------------114.0
100.0 -------------------------------------124.2
105.0--------------------------------------135.0
110.0--------------------------------------146.4
115.0--------------------------------------158.4
120.0--------------------------------------171.2
125.0--------------------------------------184.6
130.0--------------------------------------198.7
135.0------------------------------------- 213.6
140.0--------------------------------------229.2
145.0 ------------------------------------- 245.5
150.0-------------------------------------- 262.9
155.0-------------------------------------- 281.1
160.0---------------------------------------300.0

• - (in Hg) Vacuum