Pressure Relief Valve for aircon.

[Tim Leech]

I have purchase a new one for the tzi as it was removed by the a/c and he promptly disappeared! Its the right part but has come with a plastic cap with sponge in it and a weird bracket and only two o rings.

I can see that it will only fit one way but am struggling to get the pipes to connect to it as its very fiddly
Anyone fitted one before?

[Vanny]

Do you mean the pressure switch? The only relief valve that i know if is integral to the Sanden compressor. It's not normal to vent refrigerant

Edit

Following a quick Google, I think your referring to the expansion valve, which is incorrectly called a 'pressure relief valve' on some ebay listings.

In which case i change them from time to time, and never found them that tricky tbh though i change them off the car. You will typically find only 2 seals with a new one for the evaporator side (ie not for the pipes). You need to lube the seals before assembly with ND8/PAG or risk them not sealing properly and failing early.

Not sure why you would take one off, but are you absolutely sure its the right one for the BX? There is a spring inside calibrated quite precisely for the system it is designed for. Get the spring rate wrong and you'll eject the liquid refrigerant with too much pressure (leading to poor performance) or too little pressure (leading to ice ups of the evaporator), and probably find the TXV (Thermal eXpansion Valve) will hammer open and closed!

[Jaba]

If you mean the expansion valve that fits on the LHS of of the lower part of the central part of the dash console then it will probably help if you loosen the two connections that come through the bulkhead to allow those two pipes to move a bit allowing them to align better with the new valve. Its not usually difficult to get them in Tim.
Don't forget its ally and those threads are easily crossed and damaged.
The plastic cap is just a feeble but worthwhile attempt at insulation.

Stay cool.

[Tim Leech]

Thanks Guys, I will have another look when I have more time, the old one was no good so the aircon guy took it away to get me a replacement and I never saw it or him again!

[Tim Leech]

Got one side connected but I've skinned most of my knuckles so will have a look another day. Does the plastic cap need to be fitted?

[Jaba]

Doesn't 'need' to be Tim but I would pop it on to protect the diaphragm dooberry.

[Tim Leech]

Will do!

[Jaba]

Tim, sods law really works. Some more expansion valves are now on ebay for half the price you paid !!FF.

Looking at the picture of your one, which has R12 marked on it those two o-rings look like black ones suitable for R12 use only. You should use green ones with R134a. So you may need to get hold of some and swap them over.

Here's looking at you............

[Vanny]

You should use green ones with R134a.

Or brown ones, as Citroen supply, or yellow ones supplied by most Japanese OEMs, or purple ones etc

You want new Neoprene ones, basically. Avoid black seals and you should be okay. I think the black ones might be made from Vitron and harden and crack when PAG oil is applied to them (and a few years of use!).

Pretty much any car AC seal you buy new will be backwards compatible with R12, and forwards compatible with R134a and R1234yf, but only when used with PAG oil (ND8/ND12).