Hitachi indoor fan fault

[ianros]

heres a bit of a head scratcher for you guys. we had a fault where the internal fan starts and stops intermittantly(runs for 5 secs thenthen cuts out and starts again straight away and cuts out and so on.....) when on heating or cooling but will run constant on fan only. we have replaced the coil thermistor and fan control board with no success i have a feeling we may be looking at a main board but there is another cassette with a simlar fault connected to the same circuit. any ideas???:confused:
the gas charge has been checked and the other 3 systems on the circuit work fine. there are no BS boxes it is a basic and old system.

[thebigcheese]

have you checked the motor itself, could be an over load or like wise devise fitted on it

[ianros]

motors fine runs well on all speeds on fan only amps all normal windings intact

[al]

If it runs on fan only then motor and board are probably fine.
Have you a common remote control between the two units? If so try changing it.

I had an issue with a wall mount which did a similar thing, controller was at fault.

alec

[install monkey]

is it a vrv fs2 2 pipe -try the float switch for the condensate pump,u can test the indoor pcb via a self test where all outputs are sequenced to prove signal to the fan at each speed.hold check button to scroll through sensor values b1 controller temp b2 ret air b3 discharge temp b4 heat exchange temp-any fault codes on controller?