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AC Questions
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=90257		 Page 1 of 1
Author:  Steve777 [ Tue Jul 23, 2019 6:46 pm ]
Post subject:  AC Questions
So I am trying to diagnose why the AC on my CRD does not work. It was working and blowing cold 2 years ago, but it has been sitting waiting on me to do some engine work for at least 1.5 years, so something can and did happen in that time. Here's what I checked out:

1. With the AC on, the lite on the AC button is orange (which I think is OK). however there is no cooling.

2. Checked under the hood, and the AC compressor clutch never engages.

3. Also the front radiator stack fan never comes on (IIRC that should turn on once the AC button is on).

4. Tried changing the clutch relay, no difference.

5. When I short out the terminals at the clutch relay, the compressor engages, and there is some cooling.

6. When I short out the relay for the radiator fan, it goes on just fine.

7. Put a DIY freon can with gauge on the low pressure port, and it was reading ~40psi with the clutch forced on. Based on the outside temp that is about right per the chart on the freon can.

So I have not yet pulled the pressure switches and tried shorting them out (will have to look at a wiring diagram to figure out which pins to short. But I thought I would ask here to see if there is anything else I should check. It seems that the mechanical AC system does function (when the clutch and fan relays are bypassed), so the question is what can cause the computer to decide not to run the AC when there is enough freon in it and it is functional? The pressure switches of course, anything else?

Thoughts?
Author:  Steve777 [ Tue Jul 23, 2019 8:43 pm ]
Post subject:  Re: AC Questions
While waiting, decide to test the pressure switches. Tried the low pressure first, removed the connector and shorted the two terminals together. And the compressor clutch engages. Although the radiator electric fan did NOT go on (thought it was supposed to. Tried cleaning the contacts on the LP sensor but did not help, so I will be ordering a new LP sensor.

Guess my only question is about the electric radiator fan. When should that come on, as soon as the AC button is pressed in? When the some pressure or temp is reached? Anyone know how it is supposed to work?

TIA.
Author:  mrhemi [ Tue Jul 23, 2019 9:51 pm ]
Post subject:  Re: AC Questions
Sounds like you have a pooched low pressure switch. These seem to fail regularly on Liberty's. The ones I have owned anyway. The switch is relatively inexpensive and is easy to change. It DOES NOT require depressuring the system to replace.
Author:  WWDiesel [ Tue Jul 23, 2019 10:54 pm ]
Post subject:  Re: AC Questions
Steve777 wrote:
While waiting, decide to test the pressure switches. Tried the low pressure first, removed the connector and shorted the two terminals together. And the compressor clutch engages. Although the radiator electric fan did NOT go on (thought it was supposed to. Tried cleaning the contacts on the LP sensor but did not help, so I will be ordering a new LP sensor.
Guess my only question is about the electric radiator fan. When should that come on, as soon as the AC button is pressed in? When the some pressure or temp is reached? Anyone know how it is supposed to work?
TIA.

You can purchase the LP switch at Autozone or one of the other parts stores. They are fairly common.
They can be changed out without loosing freon as they have a schrader valve in the port that closes off when you unscrew the pressure switch.

As to the fan, I believe the AC system has to run for a little bit before the computer will turn on the electric fan.
Mine does not come on immediately unless the outside temperature is very high.

Replace your low pressure switch first and get the AC system working properly and then see if the fan still has a problem. :wink:
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