BX16V.com Forum

Hi all I'm drivin' my valver with a lot of fun and since all (strange) ecu errors are solved and she's drivin' like a dream it's time to solve the little things. one of these things is the aircon pressure valve. the aircon has been rebuild for r143a. I've checked the system, replaced parts necessary and filled the system. It's freezing could and the system works perfectly. only thing is the pressure valve (or is it called 'expansion valve' the one near the evaporator inside the car?) is still for r12. I'd like to replace it for the right one for r143a but which one should I get or where to get it? There's never been a BX shipped with r143a.... maybe you guys know which valve I should get? Only thing I know it's from valeo and the original r12 citroen part is 6461j3. so for example is the valve from XM r143a the same?

Why do you want to change it?

Without checking i'm pretty sure it is NOT a TXV (Thermal Expansion Valve) but an older technology. TXV's are tuned so that by the time the refrigerant has reached the end of the travel in the evaporator, it 100% state changed, ie all the liquid has expanded giving the maximum efficiency.

If you look at the valve on your vehicle you should see that there is a thin pipe coming from the diaphram on the top of the valve, which runs down to the bottom pipe of the evaporator. This temperature sensing bulb measure the temperature of the refrigerant coming out and controls the valve for maximum efficiency.

While you could tune this yourself, i suspect you are loosing less than 10% efficiency in the existing system with R134a.

I'm also pretty sure the valve is not Valeo, certainly the evaporator is not made by valeo and it is unusual for an evaporator manufacturer not to fit there own valve.

In the case of fitting the valve from a Xantia or an XM, this is likely to make the system worse. Because the expansion valve is tuned to the size of the evaporator, refrigerant type, system pressure etc and the Xantia and XM have different sized evaporators, i suspect you will make thing much much worse.

I know that recent testing on systems with R134a and a new refrigerant (R1234yf) shows very very little benefit in changng TXV settings specifically for each type of gas.

So basically, unless your going to do the full testing to check for improvement, and or you have means to tune the expansion valve settings, then i really wouldn't bother.

the initial problem was/is that my fans are now and then going to high speed when using the aircon (most probably due to the pressure in the system / heat because my coolant temp is perfect). one of the reasons could be a faulty switch/valve. I'm not eager to changing it for R143a, but if I'd change it why not for the right valve for R143a. that's the reason because the bx has never been factory fitted with r143a I don't know the right part

Sounds more like you want to change the pressure switch. The TXV doesn't control the pressure in the system, the pump does. The fans permenantly one, are only controlled by the pressure switch.

Sorry to hijack the topic, but is that valve your talking the one inside the car, that you can see if you take a little panel? I've checked that in my and it appears it's leaking gas.

I went to the citroen service site and there was no rubber seals to use there, only the complete part. Do you know how I can solve that? Does that part use rubber seals?

It uses neoprene seals, you can buy them individually in virtually any size.

This guy is fantastic;

http://www.carairconditioningsupplies.c ... n/home.php

Citroen DO sell a sal pack for around £15 which would have the seals in. But i would suspect if you can find a friendly AC engineer they would likely give you the seal for free as they cost pennies.

Ok thanks.

The air cond is a common block valve, ask any a/c parts supplier and he can supply one.
The old R12 on the BX has the same one as the MB 123 series.