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Old 04-17-2022, 04:42 PM   #1
jools99
 
Drives: 2010 Yaris hatch
Join Date: Dec 2016
Location: uk
Posts: 2
2010 1.3 UK hatch - AC operation & refrigerant leak

Am trying to fix the AC system on a 2010 1.3 VVT Yaris hatch (UK). The AC is operating but not cooling.
I’ve put a manifold gauge set on it and it shows a rest pressure of 42 psig at 16C and when I switch the AC button the low side goes down to almost zero and the high side only goes up a small amount – to around 50psig.
The fact that the low side pressure drops with the AC button tells me the compressor control solenoid must be getting a signal & operating which at least is a positive sign, but of course with those pressures it’s no surprise the system is not cooling.
I’m trying to work out how it’s controlled as I would have expected the pressure transducer to switch the system off when the low side drops down to zero – as per other cars I’ve worked on.
But I guess as the pressure transducer is fitted to the high side – the only “low” pressure it can sense is the rest pressure (on the high side) as it doesn’t know anything about the low side pressures – further I assume the 42 psi is above the min rest pressure so the system runs.
The SVP of R134a at 16c is 58 psig so I reckon there’s no liquid refrigerant in the system just gas and I found online the density of R134a as a gas at 42 psig and 16c is around 12 g/litre – and I estimate the volume of the system is around 2 litres – which means the mass of gas in the system is around 24g – which is very low compared to the factory spec of 360g.
So I think the system is simply very low on gas – hence the operating pressures and lack of cooling.
It was re-gassed a few years ago & worked fine blowing cold air – so it must have a leak – but a leak that only goes down to 42 psig is not the type of leak I’ve seen before ?! I’m used to leaks that mean a system goes down to pretty much zero.
The system had dye in and I’ve checked around all the accessible areas with UV light and can’t detect any obvious leaks. I’ve got a nitrogen set – so after evacuating the system I’ll do a proper leak down test – but would appreciate any thoughts/experience on the notes above.....
anyone seen a leak like this ?
If so what's the likely culprit ?
Is my guess on how the pressure transducer works correct ?
etc ?
Thanks
Jools
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