A/C compressor won't cycle on

[lilredwagn]

I'll go through the FSM when I get home, but in the meantime I thought I'd ask for any suggestions here.

The whole dash has been apart, but I reconnected both electrical connections (and the mechanical blend wire) to the HVAC control unit. I have NOT hooked up the vacuum yet, but I don't see how that would affect anything.

The system currently has about 70psi in it (half a can), but I tried jumping the low pressure switch anyway. I can slide the controls to any setting, but none cause the compressor to kick.

I checked fuses and swapped relays to no effect.

What might i be overlooking?

Can I run 12v+ straight to the clutch to test it, or does that risk frying something?

Thanks

[dj's 2000 xj]

By half can, do you mean a small one for recharge? If so, I would say still under pressured and needs more. I put a new condenser on my 2000 and it took more than 1 can to cycle. Hope to help.

[langer1]

What year?

[lilredwagn]

'96 .. filled with half a can of r134a. A full charge should be about 2.5 cans.

Did I "jump" the low pressure switch properly? I just connected the two leads together with a length of wire.

[solditforajeep]

I have the same prob but I didnt want to add anymore because the pressure seemed maxed out.

[langer1]

I have the same prob but I didnt want to add anymore because the pressure seemed maxed out.
About 80#?

[lilredwagn]

Forgot to connect the thermistor/fin-sensing cycling clutch switch - comes on without a problem now. Doesn't explain the odd pressure readings, but it's a start :D

[dj's 2000 xj]

Forgot to connect the thermistor/fin-sensing cycling clutch switch - comes on without a problem now. :D


D'oh! easy fix anyways, :)

[lawsoncl]

If you jumped the low pressure switch or you don't have voltage on one side of the switch, then the problem is not a low charge. Back up a step and check for voltage at the dash switch. Reading the low side pressure is dang near useless. It's nice to see how fast it's changing when the compressor is running as that can be a indicator of a low charge, but doesn't tell you the exact amount in the system. Overcharging can kill a compressor very easily. Best bet is to note what you've put in and check the fsm for the proper charge amount.

[solditforajeep]

so what is max pressure, when I was filling using a kit from walmart the gauge was reading into the yellow and thats when I stopped, I dont remember the pressure that was tho.

[langer1]

so what is max pressure, when I was filling using a kit from wal mart the Gage was reading into the yellow and thats when I stopped, I don't remember the pressure that was tho.
That's hard to answer, pressure readings are for testing and safety and will depend on temperature.
Pressure readings can't be used to tell if a systems full but can tell you with both high and low readings if a system is working properly. Point is if the pressure readings are off if can be caused by several things and over or under charge is just one of those possibility's.
Some recharge kits are refrigerant and oil for leaks where you lost a little of both some are refrigerant only.

Most of the time you need to have your system completely emptied and vacuumed then add the proper amount of oil and refrigerant by weight to the system.

[90xj06]

if it is 85 - 90 degrees out it is with in spec to be in the yellow zone but if the compressor of in that heat will cause the pressure of the low side to spike past 100psi