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A/C will not turn on

Tiny
CISCO4512
  • MEMBER
  • 2000 NISSAN MAXIMA
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 240,000 MILES
Hey all, so the A/C is just blowing hot air. I was going to recharge it and noticed the clutch not engaging at all. Checked all fuses and relay first. All is good could not figure out why but if I take a piece of wire and jump it at the relay it works clutch engages blows cold air. Changed out relay but still the same. Any ideas?
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Wednesday, September 4th, 2019 AT 4:06 PM

11 Replies

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

I attached a wiring diagram for you to view. With the key on, verify there are 2 powers to the relay.

Roy
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Wednesday, September 4th, 2019 AT 4:20 PM
Tiny
CISCO4512
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  • 6 POSTS
I checked power I do have power at relay at 5 and 2 and nothing at 1 and 3.
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Wednesday, September 4th, 2019 AT 5:04 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, the ECM is what grounds the control side of the relay to engage the compressor.

There is a pressure switch on the little line for the Freon. It has 3 wires. Test for 5 volts to the red wire with the sensor disconnected.

Roy
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Wednesday, September 4th, 2019 AT 5:19 PM
Tiny
CISCO4512
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  • 6 POSTS
Okay, I just check the pressure switch I do have 5 volts at the red wire.
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Wednesday, September 4th, 2019 AT 5:47 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, is there another 5-volt wire as well?

Roy
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Wednesday, September 4th, 2019 AT 5:51 PM
Tiny
CISCO4512
  • MEMBER
  • 6 POSTS
I double checked that just now and nothing on the other two.
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Wednesday, September 4th, 2019 AT 5:58 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
The middle wire is the signal wire and should also have 5 volts. You may have a bad ECM.

Roy
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Wednesday, September 4th, 2019 AT 6:10 PM
Tiny
CISCO4512
  • MEMBER
  • 6 POSTS
How do I diagnose the ECM to know for sure? And thanks for all your help, much appreciated.
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Wednesday, September 4th, 2019 AT 6:39 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
The 5 volts comes from the ECM.

In my first response, I attached a wiring diagram. Follow the wire back to the ECM and see if there is power coming out at that pin.

Download the wiring diagram to your laptop and then enlarge it so you can see it better.

Roy
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Wednesday, September 4th, 2019 AT 6:53 PM
Tiny
CISCO4512
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Thank you.
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Wednesday, September 4th, 2019 AT 6:55 PM
Tiny
ASEMASTER6371
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You are welcome.

Roy
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Wednesday, September 4th, 2019 AT 6:57 PM

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