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Discussion Starter #1
My girlfriend’s ‘06 Pathfinder was making ice while she was driving down the road. She told me that it suddenly quit blowing cold air, and that it began blowing outside temperature air. When I went out to check it, I noticed that the A/C switch button of the front air control would not light up.

Like a fool, I decided to remove the Cluster lid C to get to the Front Air Control unit. What was I thinking ? After struggling a while, The cluster lid came off, in several pieces. . I took the front air control apart hoping to see something burnt or broken, thinking I could just replace it. WRONG. Turns out it’s all microprocessor controlled, and I couldn’t ascertain anything. So I carefully reassembled the Front Air Control unit.

Then I decided I should check the factory service manual on my iPad. Boy was I surprised. There’s a boatload if diagnosis information in the 114 page pdf.

I’m such an idiot.

I don’t even know what I was thinking trying to tackle this.
 

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Discussion Starter #2
On page 39 of the Nissan Manual Air Conditioner manual, there’s a diagram of the harness connector terminal layout, and underneath the diagram, there’s a table for terminals and reference value for the front air controller. There’s also a receptacle on the rear of the front air control that has 8 blades in it.

Do I plug the 8 blade connector into the front air control, and check each of the 26 pins with my multi meter to the values in the chart on page 39?
 

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Discussion Starter #3
So.. more info

With the fan speed control knob in position 1, the AC light and recirc light is on the buttons are both on, BUT there is NO fan output whatsoever, but engine idle speed increases slightly, with the AC selector knob on MAX AC. (The compressor won’t run unless the AC selector knob is in max AC.) Then, when I turn the fan speed to 2, 3, or 4, there is initially very cold air coming out of the vents, the lights on the AC button and recirc button goes out, and the air temp rapidly goes to ambient air temp, and the engine idle speed dropped back down to normal (I’m assuming that indicates that the AC compressor turned off). In addition, the lights on the AC recirc buttons only come on when the right hand knob is set to MAX AC. The Potentio Temperature Control does not have to be set to the far counterclockwise position for the compressor to run. It can be anywhere.
 

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On page 39 of the Nissan Manual Air Conditioner manual, there’s a diagram of the harness connector terminal layout, and underneath the diagram, there’s a table for terminals and reference value for the front air controller. There’s also a receptacle on the rear of the front air control that has 8 blades in it.

Do I plug the 8 blade connector into the front air control, and check each of the 26 pins with my multi meter to the values in the chart on page 39?
Yes, plug the connector into the front air control, and check each of the 26 pins with your multimeter to the values in the chart on page 39 by measuring the voltage between each terminal and chassis ground. Insure that the front blower motor relay is working correctly by first checking the two fuses for it. There are a total of five fuses for the A/C system, so make sure they are OK..
 

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Discussion Starter #5
Yes, plug the connector into the front air control, and check each of the 26 pins with your multimeter to the values in the chart on page 39 by measuring the voltage between each terminal and chassis ground. Insure that the front blower motor relay is working correctly by first checking the two fuses for it. There are a total of five fuses for the A/C system, so make sure they are OK..
Thanks rogoman!

I’ll recheck those pins!

Any idea where the front blower motor relay is located?...

I found a 10 amp fuse to the right of the glove box. Not sure where the other four fuses are located. (?)
 

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Thanks rogoman!

I’ll recheck those pins!

Any idea where the front blower motor relay is located?...

I found a 10 amp fuse to the right of the glove box. Not sure where the other four fuses are located. (?)
The blower motor relay is in the fuse and relay box which is located in the engine compartment on the passenger's side in front of the firewall:
6457
 

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Discussion Starter #7
Thanks again. I’ll check that when the SO gets home. (I looked under that lid yesterday but the writing is illegible). I guess I could just swap the two similar relays to see if that makes a difference?
 

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Discussion Starter #8 (Edited)
The blower motor relay is in the fuse and relay box which is located in the engine compartment on the passenger's side in front of the firewall:
View attachment 6457
The backup lamps work, and the backup lamp relay looks identical to the blower relay, so I swapped the back up lamp relay with the blower relay, without benefit to making the blower work.

I’ll be looking online for how to test a six pin relay. (Or should I just go buy a new one?)
 

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Discussion Starter #9 (Edited)
I’m hoping I’m doing this correctly.

Based on the diagram in the ‘Manual Air Conditioner Nissan’ pdf, page 39, I’m guessing that my probe is on terminal #1(?).


Based on the table on page 39 of above, I should get battery voltage on the first six pins (the one shown, and the 5 below it) (?) but I’m not.
 

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Discussion Starter #10

With the knobs set as shown, all three indicator lights light up. Compressor runs, but no air blows with fan speed knob set on ‘one’.


Once I turn the knob to fan speed two, three or four, the AC compressor shuts off, the fan blows the appropriate speed, air is cold (very briefly), and the AC and Recirc lights go out.




Once I turn the right hand knob up one notch, the two outer lights go out, the AC compressor turns off, and fan runs appropriately on speeds two, three, and four, but not on the lowest speed.
 

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Sup Mod keeping the peace
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I’m hoping I’m doing this correctly.

Based on the diagram in the ‘Manual Air Conditioner Nissan’ pdf, page 39, I’m guessing that my probe is on terminal #1(?).


Based on the table on page 39 of above, I should get battery voltage on the first six pins (the one shown, and the 5 below it) (?) but I’m not.
The diagram on page 39 shows pin 1 being on the top row starting on the left. Your probe is pointing to pin 13. With the harness connector unplugged from the air control unit, there is no power to the unit, so of course you'll never see voltage. Plug the harness connector into the control unit and measure voltage with a very thin probe into the wiring side of the harness.
 

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Discussion Starter #12
Thanks rogoman.

I’m trying to determine if the control unit is cooked, before trying an $80 used one from flea bay. It seams like it’s dysfunctional simple from the pictures I’ve posted above.

In the event I’ve called the wrong pin, #1, I’ll try finding the true #1 pin as you have said I’m on pin 13. Thank you!

I thought the unit was powered by the white plug shown in the picture, which has a very large white and very large black wire in the five wire plug, and the large white wire does have battery voltage.

The control unit on my picture is turned 90° from the one shown in the picture on page 39 because the wire harness doesn’t allow me to fully turn it around.

It’s my understanding that the tiny pins are there to send current out the (not shown) plug to the various regions of the AC system that enable it to direct air, blow air, etc.

The back of the plug that makes contact with all the pins that are shown, that is currently not plugged in, has the wires protected and as they are exiting the back of the plug at a 90 degree angle from the plug face, and are not accessible on the back side of the plug (unless I puncture the insulation on wires).

The female holes in the plug that mate with the pins shown, are too small for the probes on both of my multimeters.
 

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Sup Mod keeping the peace
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The female holes in the plug that mate with the pins shown, are too small for the probes on both of my multimeters.
Power to the front air control unit is provided through the 26 pin connector (M49).

I use a very small safety pin to probe the wire side of a harness connector:

6459
 
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