Mitsubishi heat pump makes like jack hammer noise...

Skyline

My house got a Mitsubishi MUZ-GL09NA-U1, 9,000 BTU, Single Zone Heat Pump a little over a year ego. From the get go, this unit occasionally made the same noise, albeit it had not been this noisy until last night. The installer had been aware of it, but as usual, the unit did not make the noise when the sevice guy was here 2 - 3 times duting the last year.

AFAIK, the only moving part in the outside unit is the compressor and the fan. The noise isn't coming from the fan, it's from the compressor in my view.The indoor unit is quiete, the noise definetaly coming from the outside. About to schedule a service call for this unit.

My other unit is the Mitsubishi MXZ-3C24NA4-U1, 24,000 BTU, Multi-Zone Heat Pump with three indoor units, that quiete as a mouse. It's about six feet from the deck and I cannot heear it when there.

Anybody knows what could cause that noise for the MUZ-GL09 unit?

Skyline

Here's the jack hammer noise

GGross

Off hand sounds like a compressor issue.. unfortunately not much way to diagnose remotely. I would start back with the basics, is the unit level, is the refrigerant charge correct, compressor looks stable and level in the cabinet, lines properly vac'd? etc if this doesn't yield results I would seek to replace the compressor under warranty. This is all just based on a noise currently so its possible a good tech could find a different issue.

pecmsg

did you play the audio for the tech?

weakoak1124

Almost sounds like my unit in pump down

HVACNUT

Does it work otherwise?

With the unit running and cooling, you could pull the disconnect, wait 10 minutes and plug it back in. Then wait for it to start. It should start slow and ramp up. See if you can pinpoint it. Is everything registered? Warranty?

Skyline

Thank you all for your help….

The unit has been installed correctly AFAIK; it is in level, the unit mounted on the wall looks stable, lines properly vac'd, etc. The small unit has been making some noise, pretty much from the beginning, but never this level of noise. Of course, it didn't make the noise, when the tech was here to check out the unit.

I did email the recording of the noise to the installation company. Speaking of which, I liked this company from the get go, sales, installation and addressing the issue so far….

Both of the heat pump units had been serviced on the day prior to the hammering noise recording, just the standard spring service. The tech did hook up the manifold gauges and while I don't remember the exact numbers, both of the heat pump units had within couple of PSI the same pressure. We discussed the occasional noise that the small pump makes and of course, the small unit didn't make the noise, when the tech was here.

I did use the AC with the small unit last night and had no issue with the noise. This is what puzzles me the most. If it is a compressor issue the noise would be consistently on, correct? All AC compressors generate vibration. Maybe one of of the compressor mounting bolt is somewhat loose and occasionally makes the noise. Alternatively something else got somewhat loose, either internal or external. Like that flimsy fan protective cover, or anything else could make the noise occasionally. I don't know, but the tech will be here and let him find it. Of course, I'll let you guys/galls know what he finds.

PS: Searching on the web, found a Youtube video about the Mitsubishi heat pump units that make earily similar jack hammer noise:

https://www.youtube.com/watch?v=yg_99RmiXUI

pecmsg

Send the audio to the installing contractor.

mattmia2

Could be something scraping or rubbing intermittently, could be a charge or control issue so refrigerant floods back to the compressor under certain conditions. That it is intermittent doesn't tell you a lot about the cause.

Skyline

The tech came and looked over the unit, of course the heat pump didn't make any noise during the time when he was here.😕

He found some of the screws loose, like the fan mounting and the protective cover for the fan; the compressor screws were a OK. He tighten up, reset the screws in question and asked to monitor, if the noise comes back. He didn't think that there was any issue with the compressor, it was just humming nicely.

I do hope that the noise does not come back, but we'll see during the summer. We don't really use the AC much, maybe used it couple times so far this early season and some times last summer. That's probably the reason why this had not been detected earlier.

Thx everyone for your help…

mattmia2

It sounds like a fan scraping on a wire or a refrigerant line or piece of the cabinet or grill. Look carefully at the fan blades for rub marks on the edges somewhere.

HVACNUT

The first noise sounds like a zip tie or something hitting the fan. The second sounds like the compressor.