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A/C suddenly started blowing hot air

Tiny
JJACOB
  • MEMBER
  • 2003 FORD CROWN VICTORIA
  • 120,000 MILES
I have the car listed above it is a Police Interceptor. The A/C clutch is not activating and my A/C is just blowing hot air. I had the Freon checked and it was fully charged. I replaced the relay with a new one and it did not help. I swamped the relay with the horn relay and it did not help. If I connect the relay pins with a wire the A/C clutch activates and cold air begins blowing.

Any suggestions?
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Monday, August 6th, 2018 AT 10:49 AM

14 Replies

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

Did you check for power to the clutch relay? You should have two wires with power.

Also, check for power to the high and low pressure switches.

Roy
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Monday, August 6th, 2018 AT 12:55 PM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
I checked for power to the clutch relay and it was showing 12 volts on one terminal. Can you advise where on the diagram that the high and low switches are?
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Monday, August 6th, 2018 AT 1:32 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
As you can see in the diagram, one power comes from the ECM power relay. The other power comes from the fuse block from the fuse listed.

You need to get two powers to the relay first before moving on to anything.

Roy
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Monday, August 6th, 2018 AT 1:44 PM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
Sorry for the confusion. I have power to both terminal 1 and 3 on the relay.
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Monday, August 6th, 2018 AT 6:57 PM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
If I am getting 12 volts by putting my voltmeter on pin 1(86) and 2(85) when the vehicle is running, does that mean that both the high and low pressure switches are working properly since the PCM is supplying ground to terminal 2(85)? I tested the relay by applying power and ground to terminals 1(86) and 2(85) and the relay is clicking(switching).
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Monday, August 6th, 2018 AT 9:18 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
No, the fact that both are 12 volts tells me there is no ground. If there was a ground, then you would have 0 volts.

By testing, you are creating enough ground to make the relay click or activate.

The PCM looks for inputs from the switches before it will ground the control side to turn on the compressor.

You will need a scan tool from here forward to see if the PCM is seeing the inputs from the switches. If it does, then the PCM is bad. If it does not then either one or both switches are bad or you have a wiring issue.

Roy
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Tuesday, August 7th, 2018 AT 4:19 AM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
What is the best way to test the low and high pressure switches?
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Tuesday, August 7th, 2018 AT 9:34 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You need to check for voltage on both sides of each switch with the engine running and the AC on. There should be voltage through each switch. Back probe the wires to check for voltage.

Roy
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Tuesday, August 7th, 2018 AT 10:58 AM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
Thank you. The Ford low pressure switch has three wires.
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Tuesday, August 7th, 2018 AT 11:37 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Power, ground and a signal wire. Measure the voltage on the wires.

Roy
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Tuesday, August 7th, 2018 AT 11:45 AM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
I believe I have found the problem. One of the wires has a stripped cable(bare wire showing) and mangled
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Tuesday, August 7th, 2018 AT 11:55 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Yep, that will do it. Try and get a new pigtail. Parts stores sell pigtails of all kinds.

Solder and shrink wrap the wires together.

Roy
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Tuesday, August 7th, 2018 AT 1:28 PM
Tiny
JJACOB
  • MEMBER
  • 11 POSTS
Done and A/C is blowing cold! Thank you for your help and especially your patience, I could not have done it without you!
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Tuesday, August 7th, 2018 AT 1:45 PM
Tiny
ASEMASTER6371
  • MECHANIC
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You are welcome. Glad to help.

Roy
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Tuesday, August 7th, 2018 AT 1:50 PM

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