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A/C clutch not engaging

Tiny
LCGODFREY
  • MEMBER
  • 2016 FORD FIESTA
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 46,000 MILES
After a locksmith cut and programmed a spare key for my car the A/C compressor will not kick in. Fuse and relay are good. No power at compressor plug or at pressure switch. When jumping the relay, compressor kicks on and A/C is cold. Someone told me that the ECM could be the culprit. Locksmith said it could of not been them causing the problem. Any idea's out there?
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Monday, October 8th, 2018 AT 4:02 AM

19 Replies

Tiny
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Good morning.

The power for the transducer comes from the PCM. The PCM also grounds the control side of the A/C relay when it sees that signal.

Check for power at the transducer. It should have a 5 volt reference.

Check the fuses listed in the diagram I attached as well for power on both sides.

Roy
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Monday, October 8th, 2018 AT 7:15 AM
Tiny
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Thank you, I will check later after work.
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Monday, October 8th, 2018 AT 8:11 AM
Tiny
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Sounds like a plan.

Keep us updated.

Roy
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Monday, October 8th, 2018 AT 8:12 AM
Tiny
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Should ignition and A/C be on during voltage check? Also running?
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Monday, October 8th, 2018 AT 8:22 AM
Tiny
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You just need key on engine off.

Roy
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Monday, October 8th, 2018 AT 8:24 AM
Tiny
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Great.
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Monday, October 8th, 2018 AT 8:31 AM
Tiny
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Let me know the results.

Roy
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Monday, October 8th, 2018 AT 8:38 AM
Tiny
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Good afternoon, I just completed a voltage check and we have the 5 volts that we were looking for.
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Monday, October 8th, 2018 AT 12:29 PM
Tiny
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Okay, good.

Did you check the fuses I told you about in the diagram for power on both sides with the key on?

Roy
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Monday, October 8th, 2018 AT 12:36 PM
Tiny
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#2 has 12.5 and #1 has 2.4.
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Monday, October 8th, 2018 AT 12:49 PM
Tiny
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Those are the readings from the A/C clutch relay.
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Monday, October 8th, 2018 AT 12:54 PM
Tiny
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Pin 1 and pin 3 need 12.5 volts.

Roy
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Monday, October 8th, 2018 AT 1:01 PM
Tiny
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Pin 3 also 12.5 volts, sorry.
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Monday, October 8th, 2018 AT 1:03 PM
Tiny
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Okay, you have the powers.

The PCM controls the ground on the control side of the relay. It grounds it when it sees the correct signal from the switches.

Does the car have Freon? What is the pressure with the engine not running?

Roy
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Monday, October 8th, 2018 AT 1:06 PM
Tiny
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Suction at 110 It is about 83 degrees outside.
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Monday, October 8th, 2018 AT 1:16 PM
Tiny
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Ok, good.

At this point, you need a scan tool that can read the Ac system and see if the PCM is seeing a signal from the transducer. If it is, then you may have a failed PCM.

If you do not, then it may be either wiring or the transducer is the failure.

Roy
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Monday, October 8th, 2018 AT 1:19 PM
Tiny
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Should the voltage at at #1 also be 12v on the relay?
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Monday, October 8th, 2018 AT 1:21 PM
Tiny
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Thank you for all of you help.
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Monday, October 8th, 2018 AT 1:28 PM
Tiny
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Yes, pin 1 and pin 3.

You are welcome.

Roy
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Monday, October 8th, 2018 AT 1:31 PM

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