When I bought my 2010 G37 (seven years old), it had the greatest ice-cold A/C of any car I've ever owned. (Evidence being that the ONLY button on my dash that had the paint warn off, was the "fan - " (down) button.)

Anyway, a few years go by, and my cabin fan dies; replaced it for about $100, no big deal. Then the whole A/C system took a dump; fix including radiator was about $3k+. (Was it as cold as before? I never actually measured the original, unfortunately.)

About a year later, the fan goes out again; this time, the replacement doesn't work either, despite getting correct power (as far as we can tell). No clue, and I dropped it for a while. (It was winter, I didn't need it.)

Now, well, it's hot. Some research at the time (which I have since lost) pointed to a bad switch or intermediate module; the fan requires some sort of special "sine wave" signal, not just basic voltage. And of course, that's neither a cheap part nor an easy one to get to (i.e. somewhere in or behind the dash.)

Sorry for the long intro, but has anyone else had to deal with this switch/module? Is there any good way to diagnose it? Do I need someone with an oscilloscope? Any other recommendations besides "find the nearest cliff"?

Thanks!

 

First, is there any evidence that the blower motor is getting wet?

Assuming you have good power and ground at the fan connector, then the issue points to the PWM (pulse width modulation) signal from the amp to the blower. Unfortunately, without a oscilloscope there is no way for the home DIY'er to properly test that circuit. There is a self-diagnostic function built-in but that is not the easiest protocol to follow. Still, feel free to go here, navigate to your model/ year, and download section HAC (Heating and AC Control System) as that will have all the info you need.

That said, check to make sure you have 12V+ at the blue wire (blower connector/ key ON) and a good ground at the black wire. If those circuits are good, then more than likely the amp is the issue.

The amp is not that difficult to get to, but you will have to remove the radio headunit as the amp is attached to same:


For the 'Vert, NEW from the dealer the amp will run ≈$750. (p/n: 27760-JJ80A). I did find two (2) used amps on eBay: one for $80 OBO and the other for $250 OBO. With searching you can likely find others for sale. Some eBay sellers will sell both the amp and the radio headunit as one item and often at dirt cheap prices.

Friendly bit of advice: Please mark the two (2) connectors before you unplug them from your amp. This ensures that those two connectors go back to their proper location. It is VERY easy to mix up connectors in that area and doing so can "brick" the car.

Hope this helps some.