How to Check the Coolant Sensor Probe on CORSAIR AIOs

Many CORSAIR AIOs use a thermal sensor located on the cold plate of the cooler to measure the temperature of the coolant. This is an advantage over coolers that do not have any way to measure what temperature the coolant is. Thisn means that those are reliant on CPU temperatures to control the fans.

While not having a sensor like this is a cost effective solution since no controller is needed, it also means that the fans will fluctuate in RPM much more since CPU temps will jump rapidly up and down depending on what applications you are opening/using.

For example, opening a game and building shaders/loading a save game will often put heavy load on the CPU for maybe a minute or more, and as shown in the graph above, the coolant temp will rise steadily, giving you a much more pleasant ramp in sound level.

If the fan speed is dependent on the CPU temperature, then the fans will speed up unnecessarily.

The temperature probe is sitting on the inside of the pump housing and is surrounded by thermal paste to get contact with the cold plate.

In the vast majority of AIOs, the temperature is measured on the cold plate, and not from the coolant itself. This is to reduce points of critical failure (nobody wants coolant dripping from their AIO). This will however create a small difference between what is measured vs. the actual coolant temps, but thanks to the magic of water (specifically it's heat capacity, that difference is small enough to not worry about.

Technically yes, realistically no.

If you have an AIO with a large amount of LEDs and run them all at 100% brightness you will most likely see an increase in the temperature measured between 0 - 4 degrees. This is due to the plastic housing being heated by the LEDs (and also by the pump components, but those make even less difference to the temperature).

If this is happening then the unit is most likely incorrectly assembled and either does not have enough thermal paste mounted between the thermal probe and the cold plate, or the thermal probe is too far away from the cold plate to get a good reading.

As with all mass production, there will unfortunately always be a small amount of manufacturing errors, and if you see an abnormally large temperature increase outside of the expected 0 - 4 degrees by enabling the RGB on your CORSAIR AIO you should reach out to support for a replacement.

The problem is a very easy fix if you already have thermal paste on hand.

(It is important that the pump head stays higher than the radiator during these steps)

1. Take the AIO out of the case entirely and let it cool down to room temp (to avoid any pressure build up inside)
2. Hold the pump head as shown in the picture above and move the pump head and radiator around to get as much of the air inside the AIO up into the pump head
3. Place the pump head on a flat surface like shown in the picture above and unscrew the cold plate

4. Put a small dab of thermal paste where the thermal probe is located, and mount the cold plate back onto the cooler and screw it in (be careful to not strip the threads as the screws are self-tapping, and be careful to not get any thermal paste into the groove where the O-ring will sit)

If a small amount of thermal paste squeezes out, just wipe it off.