A/C To Cold, Compressor Won't Cycle Off?

[michael_jnel]

I am going to try and include all relevant information, but I am sure I will forget something. 97 XJ. I noticed a issue with H2O leaking into the floor, checked the drain and it is clear. I realized that the evaporator was freezing up, A/C wouldn't blow as hard as normal, and when it would thaw I would have the leak. The A/C blows super cold, I can't run it with the temp selector all the way to the left or on MAX. It even blows cold with the selector pointed in the middle position. I realized today the the compressor will not cycle off. When the mode switch is in a position the the compressor should be on the compressor and all related components come on, the compressor stays on till the switch is moved to a different position. Could it be one of the pressure sensors ? If it is can the sensor be removed and replaced without loosing all my freon? Thanks for any help, and when I get this figured out I will hit you up with another issue ( cruise and A/C on, when I hit a hill the A/C blows out defrost/inside the dash, and cruise stays on. Cant find vacuum leak under the hood anywhere) First things first

 

[michael_jnel]

Anyone?

 

[zluster]

First issue sounds like it could be the high/low pressure switch, I think the switch changed in 98 or 99 so the newer ones are a little different. I can't recall if the 97 uses 2 seperate switches or not(one high one low), but the high pressure switch sounds bad. On the 99+ the high/low switch is a single unit that can be unscrewed and replaced without losing refrigerant, it seals with an oring and pushes on a schrader valve on the line.

Your AC blowing out the defrost vents is indicative of a vacuum leak, or a weak HVAC actuator/leaking diaphragm.

 

[michael_jnel]

The 97 has 2 switches. I guess I will try the high one. If I unplug it the compressor goes off, if that means anything. I was also thinking, the compressor running all the time could cause my 2nd issue. The a/c not cutting off may be taking so much power from the engine that the loss of vacuum causes the issue with the selector switch. I may be reading to much into it tho. I have been known to do that from time to time, lol.

 

[michael_jnel]

I tried this also, I removed the low pressure switch from the line and plugged the connector in, the compressor wouldn't come on. Reinstalled it and compressor stayed on like before. I removed the high side switch and plugged it back in and the compressor stayed running like before. Also, how hot should the line on the high side be? I couldn't keep my finger on it for more than a second?

 

[zluster]

The low pressure switch is meant to keep the system from coming on if the pressure is too low(or empty, or when the pressure on the low side drops too much, so a system low on refrigerant may never cycle off, but then it generally won't ice up because its low on refrigerant), so it doesn't surprise me that with the switch out and plugged in it would be reading low pressure(atmospheric ~100kPa) and would not turn the system on.

The high side switch is trickier, it is supposed to go off when the pressure is too high, so a low pressure like atmospheric will not make the switch turn off, meaning that the only way to test it is to expose it to high pressure, like it should be getting when screwed into the high side.

Basically it sounds like the high pressure switch to me, its never turning the compressor off, the high side is getting over pressurized, and its icing up the evaporator.

Keep in mind though, even a healthy AC system can ice up when there is lots of humidity around, and knowing your part of Texas you've got plenty of that.

That sounds normal for the hot line, remember if its 80 degrees out and the condenser is icing up at 30 degrees that means the hot line is going to be ~130 degrees.

I would start with a new high pressure sensor and go from there.

 

[michael_jnel]

It was the high pressure switch that was the problem. Thanks for the help guys. Now time to track down the impossible to find vacuum leak.

 

[Lowrange2]

I wish mine blew TOO cold. Mine doesn't blow cold at all.