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A/C system not working properly

Tiny
DARREN L ANCELL
  • MEMBER
  • 2007 FORD MUSTANG
  • V6
  • 2WD
  • AUTOMATIC
  • 105,000 MILES
Replaced the A/C system; compressor, dryer, evaporator, orifice tube and vacuumed for several hours. Checked for leaks, none. Charged system to 40 lbs. Clutch will not engage. Jumpered the clutch, engaged let idle for several minutes checked pressure good. No cold air idled motor up and had Freon blow out of compressor for approximately 2 seconds. Checked gauges 150 on the high 30 on low side.
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Friday, August 7th, 2020 AT 11:00 AM

11 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Was the 150 and the 30 with the engine running or off?

40 lbs? That is impossible. The system cannot hold 40 pounds. How much Freon did you install? It only takes 26 pounces.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

I attached a wiring diagram and the location of the clutch relay.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Do you have a voltmeter and test light to do some checks?

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy
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Friday, August 7th, 2020 AT 11:33 AM
Tiny
DARREN L ANCELL
  • MEMBER
  • 9 POSTS
Hello Roy,
Thanks for the info. I checked all fuse okay. I ran a ohms test from the 85 pin to the computer grey and white wire. Good. I then jumpered 87 and 30 compressor kicked in. I put relay back and grounded the grey and white 85 wire with 2 small scribes and and the compressor kicks in. The control switches would not turn off the compressor. The engine is running a little rough as well. Could it be I’m loosing the ground on the computer?
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Saturday, August 8th, 2020 AT 12:01 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, correct. The ECM grounds the control side of the relay based on the input from the pressure switches. If it does not see the correct signal, it will not ground the control side for the compressor to come on.

Check the pressure switch for voltage. You should have 2 5 volt wires and one return to the ECM. Very those voltages.

Roy
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Saturday, August 8th, 2020 AT 12:13 PM
Tiny
DARREN L ANCELL
  • MEMBER
  • 9 POSTS
I'm getting 5v on 1---2v on the other.
Darren
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Saturday, August 8th, 2020 AT 1:12 PM
Tiny
ASEMASTER6371
  • MECHANIC
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There should be 3 wires. 2 with 5 volt and 1 with 0.

Roy
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Saturday, August 8th, 2020 AT 1:26 PM
Tiny
DARREN L ANCELL
  • MEMBER
  • 9 POSTS
Correct 5v red white.
5 v brown white.
0 grey red.
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Saturday, August 8th, 2020 AT 1:44 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, with the connector connected to the sensor, back probe the wires with 5 volts and tell me the readings.

Roy
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Saturday, August 8th, 2020 AT 1:47 PM
Tiny
DARREN L ANCELL
  • MEMBER
  • 9 POSTS
Brown wire 3 v.
Red wire 0 v.
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Saturday, August 8th, 2020 AT 2:02 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
It looks like the sensor is the issue. You should have a constant 5 volt reference and the signal should vary between 0 and 5.

Change the pressure sensor.

Roy
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Saturday, August 8th, 2020 AT 2:08 PM
Tiny
DARREN L ANCELL
  • MEMBER
  • 9 POSTS
I will get this changed out.

Thank you for your time have a good day.

Darren
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Saturday, August 8th, 2020 AT 2:45 PM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Saturday, August 8th, 2020 AT 2:50 PM

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