azrichter

I have a 4cyl 2000 Frontier, 90,000 miles that recently developed the "goes on & off randomly" problem. Usually worked in the morning, on and off when it gets warm (Phoenix summer!). VERY frustrating.

Switching A/C on would not engage compressor clutch---but then it would suddenly engage for short periods. Impossible to figure out. Sometimes hitting a bump while driving would cause it to engage or switch off. Seemed so random.

I replaced the thermal amplifier switch behind the glove box inside the evaporator box. Success!

The part (Nissan #27675Z9000) cost me $40 bucks at the dealer---though its available online for $30.

Remove the glove box and trim (6 screws).

You will see the thermal amp connector on the outside of the evap box on the left. Three wires lead into the box.

6 screws: 3 larger ones that support the box, and 3 smaller ones that hold the halves together. Remove these.

The most tricky part is opening the halves wide enough to get your hand inside. I was nervous about breaking something. But with some patience I was able to pull the bottom half down and right enough to get my hand in.

Use a light to look inside to the left of everything---follow the wires to the sensor. The sensor has a 1" prong that just wedges between the coil fins toward the back.

Pull it out and push the new one into the same place. Push it carfully---it will work its way in easily enough if you wiggle it through the fins.

The second most difficult part was trying to remove the old connector from the outside of the box. I noticed that Nissan included a small plastic bracket with a mounting hole with the new part. I just used a small screw to mount the new connector next to the old one w/o removing the old one (there was a small hole in the plastic there)---didn't want to risk breaking something. Just clipped the wires on the old connector and left it there. No problem.

This was fairly easy (30 minutes). I galls me that I see some guys reporting replacement of the "thermal unit" at a dealer for almost $400 to remedy the same condition!!!! Same part, I bet...it seems to be a common problem.