Loud clattering noise from freezer when compressor starts

[Mike Clarke]

Our Bosch fridge freezer has started to make a loud and ominous clattering noise as the compressor starts up, it then continues to run quietly. There's a recording of it on my Google Drive

The compressor starts up with a loud rattle about 3 seconds into the soundtrack after which the compressor can be heard running quietly, there's another loud clunk at 11 seconds followed by a subdued click at about 15 seconds. Before this started happening I think it used to start up with a single clunk, similar to but quieter than the one at 11 seconds, followed by a click similar to the one at 15 seconds.

The noise doesn't happen every time it starts which makes me think it might be associated with the changeover valve for switching between fridge and freezer.

Any thoughts on the likely cause and whether it's a sign of impending total failure. The freezer is an old (> 20 years) frost free one and logic suggests this is probably the time to be replacing it but none of the likely models currently on the market seem to offer such good flexibility of storage space so we're tempted to consider a repair if it's practicable.

[Peter Parry]

After 20 years it may just be the rubber mounts on the compressor have perished/worn..

[Bob Minchin]

I get this on my chest freezer when the compressor stops and the back pressure virtually stalls the motor on the power is removed. On start up the there should be no significant pressure on the output of the compressor and should start smoothly.

[Mr Pounder Esquire]

Almost certainly the compressor is on the way out. 20 years is not bad. In a past life I used to repair refrigeration and once fitted new mountings for a problem such as yours, even though they looked okay. I wasted my time, the compressor was on the way out. A new compressor is your call. Don't. Sorry .................

[tabbypurr]

A bit of rubber should fix it. It's just suspension deteriorating.

NT

[The Natural Philosopher]

+1.

[GB]

+1

But can I add that some of these motors run both forwards and reverse. That stops the cooling fans getting clogged with dust. (I have no idea how the compressor works when run either way, but clearly somebody figured out a system.) It starts up randomly going either forwards or reverse.

If the rubber mounts on just one side have perished, it would explain why it only makes a clattering sound sometimes, ie half the time, depending on which way it's running.

:)

[Mike Clarke]

Oh well, the problem has sort of resolved itself now in that it's packed up completely.

The compressor cuts in and hums loudly for just a few seconds every ten minutes or so. Despite appearing to be inactive for most of the time the casing of the compressor is permanently warm.

Looks like an emergency shopping trip tomorrow :-(

[Andrew Gabriel]

If it has an external start or run capacitor, it may be that this has died. They're only a few quid. You might even be able to nick one from something else, such as an old fluorescent lamp which may have one if it uses a magnetic ballast.

Test it by running a 60w or 100w filament lamp in series with it. It should run dimmer than normal. If it's either full brightness, or doesn't light at all, the capacitor is dead.

Not all fridge/freezer compressor motors use an external capacitor.

[Brian Gaff]

compressor mounting grommets perished? I had an Hitachi that had this, but fixing it only lasted a few months before things like thermostats started acting up and plastic cracking in the freezer part. I guess after many years things do not like being disturbed. Brian