Author Topic: Silent compressor from fridge motor.  (Read 29341 times)

Offline pycoed

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Silent compressor from fridge motor.
« on: April 08, 2024, 09:27:17 AM »
For all those who would like to use an old fridge freezer compressor as a small air compressor, I may be able to save you some trouble. I had a small compressor (Wolf Cub) in the garden shed used just for blowing up garden tractor tyres trailer wheels etc etc. this sort of thing:-

It used the very common pressure regulator controller widely available  (I know now) new for under a tenner on Ebay. Apart from the noise it worked OK for a few years until it didn’t: motor u/s, so bought another one for circa £50 which was even noisier – still for occasional use it would do. They both used the very common pressure regulator switch widely available new for under a tenner on Ebay.:-


In the garage/workshop I had a couple of old fridge compressors from long ago scrapped fridges (that’s wives for you: “It’s the wrong size, shape, colour it’s got to go etc etc.”) so I thought I’d couple one to the tank & regulator etc from the deceased Wolf. Come in handy as a blow gun for the lathe & mill without the noise of the big compessor - easy as pie I thought – all fitted with the aid of a couple of custom fittings turned to convert the fridge pipes to BSP etc. Emptied about 100ml of oil & refilled with 10W30 & away to go. No tank pressure all air leaking from what I discovered to be the unloader valve situated between the electrical glands beneath the switch.:-

 Cue a world of pain as I decided to dismantle the pressure switch to see how the unloader worked  literally HOURS later I finally got the little electrical switch return spring back in place & could refit the switch. - Still leaking & no tank pressure.
Took off the regulator switch & all guages & cleaned all thoroughly reassembled (now used about 20 yards of PTFE tape!) Result just the same.

Went online & finally found the reason: apparently there is not enough oomph in a fridge compressor to close the unloader valve against its (puny) spring so the valve needs modifying to remove the spring – see this video from about 4:40 for how to:-

Drilled out the valve keeper, removed the spring, refitted the core with a retainer of vac line from an old Merc & FINALLY all was well.

So – if you are doing this, since these regulator switches are so widely available:
1 Be aware of the need to modify the unloader valve if it  leaks – I assume it works as is for some people, since i could only find one reference to this on t’internet.
2. Unless you are a Japanese schoolgirl with uncommonly long strong fingers, do NOT dismantle that bloody pressure valve If I’d known they were £7.99 delivered on Ebay , I would have introduced it to Mr Sledge & his friend Mr Anvil.