Engine temp and AC

[Matt Knight]

I normally drive my 1991 NSX with the AC off and the temp gauge (after warming up) is rock steady at 1 line below the halfway mark.

Today while running the AC I noticed the temp was registering 2 lines below the halfway mark. I was cruising on the highway at 60mph in 5th gear and when I turned the AC off the temp came back up to normal within a few minutes. Turning the AC back on resulted in the temp dropping again. I repeated this for a couple of cycles and the results were consistent.

I've never noticed this before; is this a problem?

TIA,

Matt

 

[davidf]

The condensors are not positioned in front of the radiator thus should not directly affect the engine temp or gauge reading. That is weird. Mine stays rock steady either way.

 

[NRG TRADR]

Mine stays steady either way too. I don't know exactly how the NSX cooling fan is setup but on some other cars this happens if the low speed fan circuit is not working (but should be running), and when you switch the AC on the high speed circuit kicks on creating a noticeable temp difference. However it seems this large effect would be more noticeable stopped at idle when there is no airflow. Any updates?

 

[Matt Knight]

Drove to work today; the car warmed up normally and the temp gauge stayed constant with the AC off or on.




Today's temperature is about 20 degrees less than when I noticed this problem and today the vents were blowing warm air (both times the CCU was set to 70 degrees).

In my original post I neglected to mention that this happened while driving in the rain. And as they say on Mythbusters "Well there's your problem.".

Any insight would be appreciated,

Matt

 

[Honcho]

I normally drive my 1991 NSX with the AC off and the temp gauge (after warming up) is rock steady at 1 line below the halfway mark.

Today while running the AC I noticed the temp was registering 2 lines below the halfway mark. I was cruising on the highway at 60mph in 5th gear and when I turned the AC off the temp came back up to normal within a few minutes. Turning the AC back on resulted in the temp dropping again. I repeated this for a couple of cycles and the results were consistent.

I've never noticed this before; is this a problem?

TIA,

Matt

This sounds like an electrical problem, as the A/C and coolant systems are totally separate. Maybe the A/C switch and temp gauge share a ground? Or the gauge sensor in the water jacket?