Last night our mitsi heat pump starting making louder than normal noises.   Going up close it was almost like its 'pulsing' or 'surging', it sounds like it is blowing harder for say 2 secs then softer for 2 secs, then harder for 2 secs and so on.

We've never heard this before.  Did the old turn off and on again, no change.

Anyone know what this could be?  I've turned it off for now in case it is serious, and will get someone in that's the thing to do.  But perhaps there's a known solution out there.

Thanks