Thanks,
with the modifications to the stereo, I found two empty plugs and no sensor.
Turn the key to run, turn the fan to auto, wait one min on every setting on the temp setting. push the off and auto and nothing shows.
First off, there are two test procedures. The self test (which is what you were doing) and the functional test. The following is a link to the Wiki outlining the two tests.
https://www.nsxprime.com/wiki/Troubleshooting_the_Climate_Control_System
The internal cabin temperature sensor is, as jwmelvin notes, part of the aspirator fan assembly which fits just behind that little grill below and to the right of the ashtray thingy (or whatever that is supposed to be). If there is nothing behind that grill, then the aspirator fan assembly and the sensor has been removed. It may have also been disconnected. This is not uncommon because they can become noisy when they get dirty (a fixable problem). If the aspirator / temp sensor has been removed / disconnected, this should show up as an open sensor in the self test mode. If the sensor has been disconnected or is otherwise non functional, the climate control should continue to work; but, only in the manual mode. If the self test procedure does not light anything up on the CCU display, I think that means that everything is working (as far as the CCU is concerned). Try the functional test and see what happens.
Your description of how you did the self test procedure is a bit unclear. My recollection is that you set the temperature to minimum and wait 1 minute and then set the temperature to maximum and wait 1 minute. Not 1 minute on 'every' setting. If in fact you meant the 1 minute on min and 1 minute on max, the rest of the procedure sounds correct. If nothing lights up on the display, that means everything is working, including the internal temperature sensor. It has been 5 years since I tried the self test so I may be a little fuzzy on the specifics.
You used the term unstable. That implies that the temperature is varying up and down by significant amounts with no user adjustments. Or do you mean that there is just poor resolution on the temperature setting (either hot or cold and not much in between)? If the latter, I think that is not uncommon. The NSX has a great big glass greenhouse and if you have a black interior, suffers hugely from solar heat gain. If it were not designed as a car, it would probably make a great solar heat collector.
The NSX has an optical sensor on the dash which provides a 'solar gain' input to the CCU, effectively causing the AC to work more on sunny days. If it is sunny outside and the ambient is over 40 C, the CCU is probably going to crank it to the max just to keep the 'average' cabin temperature close to 25 C. Your feet are going to be cold when that happens. Try experimenting by covering the optical sensor to reduce the solar gain input to the CCU if you are running in auto mode. You may also have more success running in manual mode. That is what I do on hot clear days.
