Unloader valve sticking problem ☹️

Digitalflyer

Young Tutorling
Hi folks got a slight problem with my unloader valve.
I have a small fridge compressor sat on top of a 6ltr tank, that feed to a t junction that one port goes to the tank and the other to the unloader valve on the switch. Everything has been working fine up until the other night when I'd been AB'ing for a while, when suddenly the compressor kicked in at low pressure, but nothing going into the tank, deeper investigation found that the unloader appeared to be jamming, and when I lifted it, it filled the tank as normal. When full unloader switches power off and discharged excess, only I noticed a bit of oil mixed in with discharged air and a bit of moisture.
Also when it was leaking I notice oil vapour coming out like smoke.

Is the oil jamming the unloader (although it feels loose enough)? or is it a case that the switch unit has has gone up the shoot? and it there any problem with oil getting in the tank?

I have moisture and oil traps fitted in to outlet hoses and nothing coming out there except clean air.
 
Its a combination of a check valve and a piece that works like a diaphragm regulator, It lets the compressor start without any backpressure and closes off as it gets air normally. Then bleeds off when the pump quits running.

I would guess that yes the oil is causing the valve to stick....What was the original refrigerant type? That will tell you what oil was likely used and many of them get sticky when exposed to air. You can probably clean it out with mineral spirits,


That is the usual problem with fridge compressor conversion designs, most fridge pumps actually suck up and circulate the oil by design to keep the motor cooled, the original circuit returns that oil to the crankcase. Get rid of it and it is forever emptying its oil out. It will get low and burn up. (mineral oil is a good replacement for most)
Fridge style air compressors commercially made use an internal oil cooler design instead.

You can manually put it back in every so often or you can make up your tubing so that there is a nice vertical section after the compressor and before going anywhere else, preferably with a big diameter. That will catch oil and let it return to the compressor when its off.
 
It the little plastic piece that pops up when pressure is increased and drops when required pressure has been reached.
The original oil was R34 type which was drained off, and replaced with a thin 3 and 1 oil, which is a thinned mineral oil (although I have just found out that some make have ptfe and silicone added, therefore now wondering if this is adding to the problem). I've moved the fridge motor a metre below the tank, to help any stop/lesseon extra oil from getting to the tank. I've not not been able to use it for a few days due to health reasons, but noticed yesterday, that moving it seems to of helped, but if it sticks then a slight tap on the switch case will release it and all well for a while.
I did dose it with switch cleaner at weekend, but still it sticks, unless it's going to need several doses to clean it out.
I've read that some have used 40/30 engine oil, but this to me I think would be to thick, and gunk it even more.
 
It the little plastic piece that pops up when pressure is increased and drops when required pressure has been reached.
The original oil was R34 type which was drained off, and replaced with a thin 3 and 1 oil, which is a thinned mineral oil (although I have just found out that some make have ptfe and silicone added, therefore now wondering if this is adding to the problem). I've moved the fridge motor a metre below the tank, to help any stop/lesseon extra oil from getting to the tank. I've not not been able to use it for a few days due to health reasons, but noticed yesterday, that moving it seems to of helped, but if it sticks then a slight tap on the switch case will release it and all well for a while.
I did dose it with switch cleaner at weekend, but still it sticks, unless it's going to need several doses to clean it out.
I've read that some have used 40/30 engine oil, but this to me I think would be to thick, and gunk it even more.
Id try to clean it again, if it seems to help at all id try a couple more times, if that doesnt work then you might end up having to replace it....A lot of those work with a ball on the inside, when it starts to wear it can become almost like a press fit in its little socket.
 
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