I have a 95 xj, and i am having ac problems. I checking and i am not getting power to the compressor. I swapped the relay with a good one to check that, and that didn't help. I jumped the LP Sensor(?? beside evap canister) and that did nothing. When turning on at dash it idles up to prepare but never comes on. What other sensors are in line that can control the compressor. Compressor is good, i jumped it to 12v real quick to check and it kicked on. But before i go and spend the money to check to see if it is charged, i want to check everything i can. I do have pressure in lines and think it is enough. Thanks for any help.
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95 xj AC Compressor not getting power??
- Thread starter wbarber
- Start date
Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
The 95 FSM shows the circuit this way, tracing back from the clutch relay. The clutch relay has four terminals active: #19, dark blue/black goes to the clutch. #20, dark blue/orange, goes to terminal 34 of the PCM (A/C clutch relay control); # 17, light green, goes to terminal 28 of the PCM (A/C pressure switch output) and also splices directly to the line between the dash switch and the low pressure switch. Relay terminals 20 and 17 are the two sides of the solenoid circuit. #17 is positive, and 20 negative. The PCM on this vehicle usually controls things via the negative. Finally, terminal 16 of the relay (dark blue/white), which is the source of the positive current that actuates the clutch, gets its power from fuse 11 in the Power distribution center. This same circuit also feeds the positive side of the solenoid in the radiator fan relay.
Terminal 27 on the PCM is the A/C cycling switch sensor, and a light blue wire from this goes back to the AC cycling switch, which the diagram shows as a resistor. The PCM line is a center tap off this, with one end of the resistor going to ground (black wire), and the other (dark blue/orange) to the low pressure switch, and thence ( light green) to the mode selector switch in the dashboard.
The AC cycling switch is down in the lower right, under the instrument panel near the heater blower resistor.
So basically, when you turn on the dash switch, you should immediately see positive voltage at terminal 17 of the clutch relay as well as terminal 28 of the PCM. If everything is correct in the system, then this positive voltage will also be passed through the low pressure switch and the cycling switch into the PCM via terminal 27, and will cause the PCM to switch on the negative side of the circuit through its terminal 34, whereupon relay terminal 20 will go negative, actuating the clutch. Remember that in this system, control is done through the negative side. If you are getting the positive to the relay but not the negative, suspect the pressure switch or the cycling switch. If you are not getting the positive to the relay, then the dash switch is not providing it. The dash switch gets its current through fuse 5 in the fuse block (30 amp). It comes in at terminal 4 and out at terminal 5.
If the relay is being actuated, but the clutch is not coming on, either the relay is bad, or its terminal 16 is not getting the power from fuse 11.
Terminal 27 on the PCM is the A/C cycling switch sensor, and a light blue wire from this goes back to the AC cycling switch, which the diagram shows as a resistor. The PCM line is a center tap off this, with one end of the resistor going to ground (black wire), and the other (dark blue/orange) to the low pressure switch, and thence ( light green) to the mode selector switch in the dashboard.
The AC cycling switch is down in the lower right, under the instrument panel near the heater blower resistor.
So basically, when you turn on the dash switch, you should immediately see positive voltage at terminal 17 of the clutch relay as well as terminal 28 of the PCM. If everything is correct in the system, then this positive voltage will also be passed through the low pressure switch and the cycling switch into the PCM via terminal 27, and will cause the PCM to switch on the negative side of the circuit through its terminal 34, whereupon relay terminal 20 will go negative, actuating the clutch. Remember that in this system, control is done through the negative side. If you are getting the positive to the relay but not the negative, suspect the pressure switch or the cycling switch. If you are not getting the positive to the relay, then the dash switch is not providing it. The dash switch gets its current through fuse 5 in the fuse block (30 amp). It comes in at terminal 4 and out at terminal 5.
If the relay is being actuated, but the clutch is not coming on, either the relay is bad, or its terminal 16 is not getting the power from fuse 11.
- Location
- Houston, Tx
does it have a charge in the system?
the compressor will not kick on if you don't have freon in the system, it does this to protect you from burning up the compressor. the a/c fan also will not kick on if this is the case.
the compressor will not kick on if you don't have freon in the system, it does this to protect you from burning up the compressor. the a/c fan also will not kick on if this is the case.