Can't find a condenser!!

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Re: Can't find a condenser!!

Postby poprivet » Thu Jul 23, 2015 2:58 pm

Thinking aloud, I'm no expert but hey!

The oil will be PAG I assume as it is 134a, I guess the system was open for quite a while, PAG is highly hygroscopic, maybe moisture in the system is freezing in the expansion valve?

Reading up on 134a it seems there may be incompatibility with the normal receiver dryer material causing it to break down, maybe that is causing a blockage?

Is the heater water valve shutting? they are normally open but close with vacuum.


There is information on the later XJSs that were designed for 134a but they use many different components not least the compressor and condensor, however, there must be many earlier systems converted successfully. Surely not all are either still on R12, a drop in gas or not working at all?
1988 3.6 XJ-S coupe
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Re: Can't find a condenser!!

Postby davidr » Sat Jul 25, 2015 11:16 am

Hi Pop and thanks for your thoughts - the oil was drained as far as we could when the system was converted. Most oil sits in the compressor and a new one was fitted as the old one had seized. The oil added back was ester as its compatible with both the old oil and PAG oil and so wouldn't react and cause an issue.
Mindful that the system was open for quite a while we left it on vacuum for much longer than one would normally in order to boil off any moisture. The system wasn't left completely open as I plugged all the hoses etc when I was working on it.
A new receiver/dryer was fitted when I put it all back together and I'm pretty sure that it's compatible with the new gas. If there was any residual moisture (which I think unlikely considering the measures we took) the new receiver/dryer should have captured it.
The heater valve is fairly new and is working properly.
1996 XJS Celebration Conv. (shown on the JEC stand at NEC Nov 2015)
2001 XKR Convertible

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Re: Can't find a condenser!!

Postby almcl » Sun Jul 26, 2015 8:20 pm

Coming somewhat late to this, but several things occur.

If there's foaming in the sight glass then there isn't enough refrigerant. I know you said 1100 gms (the Tech services bulletin on retro fitting R134a specifies 1150) but getting a bit more in there might help.

The high and low side pressures should NOT be similar. Low side (depending on temp) should be in range 20 -30 psi; the high side (again depending on the temp of the condenser) can be up near 200. If the high side isn't making this then the output from the compressor is being blocked somewhere along the way. Receiver drier could be one possible culprit. What were/are the high and low side pressures?

As regards performance, I've done three of these systems now and have always managed to get the output air temp from the face vents down below 4°C when in full cooling mode (image below in case this sounds like an idle boast). So while 134a may not be quite as good as R12, it should still produce a chilly blast.
air con performance.jpg
Air con test
Al McL
'93 XJS 4.0 - '05 X type Est 2.0D - '13 XF 2.2D Sportbrake

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