A/C not working and a question for Mark at Wrangler Fix about ECUs

[JPHikr]

Our Jeep sat for a 6 months not being used.
I put a new battery in it along with some fresh fuel and it fired right up.
So I took it out for a drive and the AC did not work.
The clutch was not engaging on the AC compressor.
All the HVAC controls are in the on settings.
Checked the fuses in the engine compartment, all showing 13.5 volts with engine running.
also the The AC Compressor Clutch Relay has 13.5 volts to supply plug but not turning the relay on.
Swapped the AC relay with the horn relay and the horn worked so relay is good.
Opened the glove box and checked fuse #8 and #11 They are showing 13.5 volts. PDC 40 amp fued is goog and 13.5 volts to it
Ok the PO had install a switch to disengage the AC compressor while still having the blender door and temp controls working.
Took the dash apart to get to the switch which is mounted next to the power port.
Switch worked continuity between the two posts when in the on position.
But with the engine running there is no voltage at the grey/ pink wire (this is where the override to the AC compressor switch is installed or any of the Grey/ pink wires}, hmm so I busted out the workshop manual Section 8 Wiring.
It is not your typical road map style wiring diagram.
So I had to sturdy it for a bit to see what is what.

Looking at circuit C
PDC The AC Compressor Clutch Relay has 13.5 volts with the key in the run start position engine running.
If I jumper the relay connection to engage the clutch I will be able to check the Hi and low side pressures.
Do not want to damage the ECU so I want to only power the compressor clutch by enegizing just that circuit .
Is this OK to do?

A question for Mark at wrangler fix, Can you tell me how the AC is controled by the ECU?

 

[Mall'er]

Jumper the low pressure switch to see if the compressor engages.

If it does, most likely low refrigerant.

If it doesn't, then start the ac troubleshooting in the workshop manual.

 

[JPHikr]

Opps should have put year and model:
2005 LJ Rubicon

 

[JPHikr]

Going out in a bit and will try energizing the low presure switch to see if the compresor will engage the clutch.

 

[Mall'er]

I am sure you know, but don't do it at the relay, do it at the switch itself.

 

[JKP]

And why was a switch added? Bad HVAC control switch?

 

[JPHikr]

Not sure why he did that, but the blower switch worked but now is not getting any voltage from thr PDC.

 

[JKP]

Have you pulled out the HVAC controls to look at the wiring on the back? A blower motor that's going bad will melt the connectors and wiring. The right knob is the master on/off.

You can get a new HVAC control panel made by Standard Ignition. Replaced mine awhile back when the fan switch got wonky.

 

[JPHikr]

The problem is not getting any voltage thru the grey/ pink wires to the switches.
That is why I was hoping to have Mark explain how the ECU controls the AC system.

 

[JKP]

It doesn't.

Try pushing the key in and see if the blower comes on. When the key is worn, certain things won't work right. Even better if you have an unused key.

 

[Steel City 06]

Note that most of the switch/sensing circuits are switching to ground, not to +12v or +5v. Basically the "sense" side always has a higher voltage, and the switch completes a circuit to ground. The relay or PCM then senses a current flowing through it, and therefore knows the switch is closed.

 

[JPHikr]

I have three keys I will give them a try in the morning.
I will also test fuse #7 for voltage.

 

[JPHikr]

Ok I figuered it out.
My AC manifold which I have had for 15 years,the LPS fitting did not press down deep enough to push the schrader
valve down.
The one on the left is one for my manifold on the right is one that came with some freon I purchase off Amazon.
Hooked up the plastic one and was able to see that I only hand 5 psi in the LP line.
Then I put in a can of freon and the compressor kicked on,
I have used my maifold to recharge our 77 chevy C20. 80 FSJ Cherokee (sold it in two hours on Sell a Jeep. Great place to sell your Jeep) and our 83 Ford E350 Class B RV both the indash and the roof AC units.
Now blowing cold that said had mouse fur blow out the defrost vent and the control will not open tje other vents.
I am going to go in to the deforster vent with a smll tube hook to my shopvac and see if there are any mouse bones keepin the blend doors for working correctly.