Help heating problems

[Dingelnutzz22]

the temperature on the instrument cluster showing normal temp just under half
But when im turning up the heat to 90 it’s only blowing cold air!
The car never over heats
I check the rad hose in the front end
Both top and bottom hose are warm
Could it be a faulty thermostat? Or blown head gasket?

 

[Old Guy]

Check the heater control valve on the left side of the heater housing (facing forward) in the front compartment.



The clamps holding the control cable may have come loose allowing it to slip. If the cable is in place and not slipping, with the engine running and up to temperature, have someone operate the CCU temperature control to see if the cable moves. If it doesn't move:

1. the valve may be jammed and require replacement. You can check this by disconnecting the cable to see if you can manually move the valve.
2. the cable control motor may have failed. I think if you run the CCU self test it will diagnose a failed motor
3. the CCU temperature control / measurement may be bunged. I think the CCU self test will diagnose a temperature sensor problem

 

[Jerry@Mobile]

Mine was the opposite. Once the heat was on, it would not turn off. It turned out to be the control motor. I manually turned the valve to off as I am in Florida and don't use the heat. I did order a motor and got it from Japan after a six month wait. I have yet to install it. Good luck. Jerry

 

[Dingelnutzz22]

Mine was the opposite. Once the heat was on, it would not turn off. It turned out to be the control motor. I manually turned the valve to off as I am in Florida and don't use the heat. I did order a motor and got it from Japan after a six month wait. I have yet to install it. Good luck. Jerry

U mean the digital controller?

 

[Honcho]

U mean the digital controller?

No it's the actual electric motor that pulls the cable on the water valve. It sits under the HVAC unit.

 

[Dingelnutzz22]

No it's the actual electric motor that pulls the cable on the water valve. It sits under the HVAC unit.

Do I have to take out the whole dash? To get to it?

 

[Honcho]

Do I have to take out the whole dash? To get to it?

No- you should be able to remove it from underneath the HVAC unit, but it's going to be very, very difficult. IIRC there are three screws holding it to the HVAC. Then, you have to release the cable. Access is super tight- you'll need a flashlight and a mirror.

When I did mine, the SRS module was already removed, so I had a lot of room to work. I would recommend setting the motor at either full cold or full hot so you can remember what the cable setting was when you put it back together.

 

[Old Guy]

Do I have to take out the whole dash? To get to it?

No; but, you are likely going to need bandages for all the scrapes on your hands. Go to the NSX Prime Library and download a copy of the service manual for the gory details on the location of the servo motor and testing it.

Have you confirmed that the cable is not moving and that the motor that controls the cable has failed? This is not something that you want to be doing unless you are sure that it is a failed motor. Also, as @Jerry@Mobile notes, have a replacement motor in hand before you go in for the deep dive. No point pulling stuff out and then finding out its a 6 month wait.

 

[Dingelnutzz22]

No; but, you are likely going to need bandages for all the scrapes on your hands. Go to the NSX Prime Library and download a copy of the service manual for the gory details on the location of the servo motor and testing it.

Have you confirmed that the cable is not moving and that the motor that controls the cable has failed? This is not something that you want to be doing unless you are sure that it is a failed motor. Also, as @Jerry@Mobile notes, have a replacement motor in hand before you go in for the deep dive. No point pulling stuff out and then finding out its a 6 month wait.

Yes the cable isn’t moving when I changed the temperature settings at all, how will I know if the main temperature controller isn’t damaged or not working at all,

 

[Old Guy]

Check page 22-12 of the service manual

Factory Service Manuals

As our NSX continues to age, it will become more and more important for member to be able to service their cars. Most Acura dealers no longer employ technicians who are familiar with the NSX, as the original techs are long gone or retired. As...

www.nsxprime.com

This describes the self diagnosis test and the next page describes the function test. The air mix control motor does double duty as the control for the heater valve. The test should indicate whether the air mix control motor has failed. The test should also indicate whether there is some other problem such as a temperature sensor that may be preventing the motor from operating.

Pages 22-26 and 22-90 describes the test for the air mix control motor to confirm that the motor is functional / non functional. Unfortunately, this describes the test from the plug attached to the pigtail on the motor which means that the test is effectively impossible to do with the motor in place unless you fabricate an adapter cord to bring the motor terminals out to a location where you can attach the tester and apply voltage. However, if you look at the wiring diagram for the CCU on page 22-11 you will see that all of the air mix control motor terminals are accessible from the plug on the back of the CCU which should allow you to carry out the service manual tests on the motor once you have removed and disconnected the CCU and can access the plug on the back of CCU. This diagram from the ETS shows the pin connections for the air mix control motor plug and the matching pin connections on the CCU plug





If you run the the self diagnosis test on the CCU and it indicates failure of the air mix control motor and you are not particularly comfortable with reading electrical diagrams and doing electrical tests I would skip that and just move to replacing the air mix motor. You do run a small risk doing this because the problem could be in the wiring harness between the CCU and the motor; but, unless somebody has been messing around with the vehicle wiring the wiring harness on the NSX generally falls into the last thing to fail category so this is a low risk.