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AC Diagnosis help: 2007 Altima 2.5 Forums > > AC Diagnosis help: 2007 Altima 2.5 AC Diagnosis help: 2007 Altima 2.5
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Old 07-19-2019, 10:03 AM
jbryan189 jbryan189 is offline
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2007 Altima Sedan
Join Date: Jul 2019
Posts: 1
Default AC Diagnosis help: 2007 Altima 2.5

My recent purchase of a 2007 Altima with a 2.5 engine, has been a challenge.

I replaced the AC compressor, vacuumed and charged. Turned the system on and it immediately blew the 10 amp fuse. Replaced fuse and it did it again. Replaced the 10 amp again, and now it has power.
Using the service manual, the wiring appears to be good with very low impedance. The clutch is around 440 ohms so thats making just above 3 amps at 12 vdc to operate. I have not taken 12 volts directly to the clutch.
It looks like the AC relay is not pulling in. (the one near the obd connector) Swapped relays with the blower fan and it works fine in the blower receptacle.
I am a bit confused about the signal making it to the BCM or ECU, and what controls that? I found the pressure switch but no idea where connector M37 is located. The fan controls look good as the doors are all switching using the fan controls. In defrost mode the compressor isn't turning on either.
Is there a low pressure switch in the loop? I have good pressure on both sides reading about 100 psi at 102 F ambient.
Help me quit sweating!

Last edited by jbryan189; 07-19-2019 at 10:05 AM.
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Old 07-23-2019, 10:50 PM
smj999smj's Avatar
smj999smj smj999smj is offline
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Join Date: Jun 2012
Location: Prospect, VA
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If you have a FSM, all of your answers are located in it if you do a bit of searching. There are harness diagrams in the FSM that show where the connectors are located. The "M" in front of the connector indicates it is part of the Main electrical harness. I believe the harness layouts with connector locations are in the Power & Ground section. If not, they should be in the "EL" chapter. In the HVAC section, there should be a "Circuit Description" which tells you what everything does. I believe Nissan has gotten away from low pressure and high pressure switches and replaced them with a triple pressure switch. However, if there is a low pressure switch, it will be shown on the electrical diagrams for the A/C system.
As far as testing the circuit between the IPDM (which contains the A/C relays) to the clutch, you can perform an IPDM active tests. Once initiated, it will turn on and off multiple components, including the wipers, headlights and fog lamps, A/C clutch and electric cooling fan(s).

Here's a YouTube vid on how to activate the active test: YouTube
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