Compressor not engaging

[JMS1868]

New to the site so thanks in advance.
having several ac issues.

Girlfriends 2009 Edge 200k miles, had issues with blower motor working intermittently. I replaced the blower resistor and it worked fine for two days. Now having same issue. Thought it was a bad blower but it randomly will kick in and blow at high speeds. Also, the compressor will only engage for about a second or two before shutting off again. Connected gauges and it shows high pressure but I believe this is because compressor is not engaging. I added a little Freon but it still will not engage. I also noticed front fan ( I believe for condenser) is running more than usual.

Since this is multiple issues going on, can this be a PCM issue? How can I test, or should I replace the low pressure switch?

Is the radiator/ condenser fan running more due to a hotter condenser caused from low Freon?

I am mechanically inclined but at a loss. Do I continue putting Freon in? I had compressor issues on my truck and after adding a can the compressor kicked on, but is not doing same on the Edge. 
She has the dual climate auto controls.
All help GREATLY appreciated.

[JMS1868]

Can anyone advise where the ambient air sensor is located? Is it in the fender well, bumper, grille? I know the Edge has an ambient air sensor and a climate control sun sensor on the dash area. Are there any other climate or air sensors in the a/c system?

[charlersfosho]

I am also fighting my compressor not engaging. I still need to do some more troubleshooting but I am starting to feel mine might be PCM related. I already had my PCM replaced due to faulty coil packs. 

 

The Ambient Temperature sensor is behind the front bumper cover. Things might vary slightly as I have the 07 Manual. When taking off the front bumper don't forget to unplug the fog lights.

 

See photos below.

[enigma-2]

On 7/20/2020 at 5:17 AM, JMS1868 said:

New to the site so thanks in advance.
having several ac issues.

Girlfriends 2009 Edge 200k miles, had issues with blower motor working intermittently. I replaced the blower resistor and it worked fine for two days. Now having same issue. Thought it was a bad blower but it randomly will kick in and blow at high speeds. 

Talk about the blower first. The blower on a manual system gets its power from fuse F63 in the battery Junction box. Runs to the blower motor relay then to thr blower motor. The ground for the motor is found through two sources. On high speed, its grounded through the switch.

 

(If its intermittent on high there's three possibilities. The fuse is intermittent, the relay is not holding under load, the motor is failing or the switch is defective).

 

On mid-high or mid-low it first passes through resistors in the resistor pack. On low it's passes through all of the resistors and is always on low unless a higher speed is selected. 

 

The blower relay is triggered by the HVAC module. 

 

I would test the black wire at the blower to see if voltage is constant.

 

If it is, it's the blower, or switch.

 

If it is not, fuse 63, the relay or the HVAC module. (Relay power comes through fuse F45 in the smart junctiln box, another possibility.) I'd also look at the conbectors for corrosion. 

 

As for the compressor,  there's no common point and you need to pull codes to determine where to start.  Do NOT add more refrigerant. You can do real harm if you do know what you're doing. {Start with the codes}.