[Richard L]

The FCM should not sound any different in cold or hot conditions.

There is an electronic circuit board inside the FCM performing two tasks. It converts the raw flow sensor pulses for the HFS-6 and drives the inline valve within. The driver can be temperature sensitive. If you know how to solder, I can send you instruction how to bypass it. It is a five-minute job.

This will avoid the necessity to relocate the FCM. Some time in the future when the system behaves well, I can convert the controller to V3 if you return the controller back to me. I don't charge for doing this, but you have to pay the return shipping.