View Full Version : Hitachi RAM-90QH5 possible locked compressor?

06-08-2017, 07:37 PM
Hello! Hopefully this is the right place for this...

I'm trying to diagnose a fault with my Hitachi multi split. I have a feeling the compressor might have locked up, but figured a second opinion couldn't hurt.

When the unit tries to start up, the fan runs, and an increasing buzzing is heard from the IPM area as it tries to start and ramp up the compressor. This only about a second after which it cuts off and LEDs 301 and 302 blink twice, suggesting over current.

I've check the compressor windings, and they're all in spec. I've put a DC amp clamp on each phase to the compressor, and when it tries to start up, on two of them it hits about 50-60 amps, on the third it goes over 100 and my amp clamp stops reading before it cuts off again.

Reversing two phases makes no difference - if the compressor itself is moving at all briefly I can't hear it in either direction.

I can't think of anything else to try to diagnose whether its the IPM board or compressor at fault. Could the IPM fail in such a way, that the phases aren't actually rotating and its just dumping the voltage on all three in sync? I have ~320v at the input to the IPM as it starts.

For the fault condition as indicated by the LEDs, the service manual says to replace the IPM board... but then, the same manual never points the finger at the compressor under any circumstance.

Hoping its not the compressor but wishful thinking I suspect... any suggestions welcome!

06-08-2017, 08:38 PM
I was just thinking... I may have not changed the amp clamp to DC... so those readings might be complete rubbish. Wish it would default to DC, that's all I use it for!

07-08-2017, 02:01 PM
If you can do safely, check voltage at compressor at start, 3 lines should be roughly the same, if they are most likely compressor is locked, but for similar faults (other brands), i change the board and compressor anyway.

07-08-2017, 11:39 PM
Thanks - I'll check those out and the things in that other LG thread.

I suppose pre-empting a dead compressor, is a JU1318D1 and IPM etc still likely to be something available for this?