BX Air conditioning R134A conversion (all you need to know thread)

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Jaba
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by Jaba »

Aaah I get it now. This is normal behaviour with the blower motors on high speed because you are blowing air through the evaporator at a higher rate than the aircon system can cool sufficiently so the compressor will be on permanently to try and provide enough cooling.
You might be getting low on refrigerant as this will reduce the aircon performance. Have you had it recharged recently ?
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by senmathal »

Maybe it´s my explanation that is odd :) What do you mean sounds odd? What I mean is that the high speed only com on when I short circuit the pressure switch but not when I run the A/C.

/Mats

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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by Jaba »

senmathal wrote:
Thu Jul 20, 2017 8:47 am
Maybe it´s my explanation that is odd :) What do you mean sounds odd? What I mean is that the high speed only com on when I short circuit the pressure switch but not when I run the A/C.

/Mats

Yes, I have got that now.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by senmathal »

Sorry I did not see your last answer when I did my reply. Yes I have recently have my A/C charged. But it has not been in use fore a couple of year so maybe it´s a leakage somewhere in the system. I think I will take it to the garage and looked at it with ultra violet light. But it´s still very cold air blowing and it´s work properly. Maybe the cooling fan will get in high speed a hot day. As I understand the pressure will rise when the system get hotter. Sadly this summer in Sweden seems to be the coldest summer in many year.

/Mats

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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

Conversion to R134a
O-rings

Have just taken delivery from Citroen of the four sizes of pipework O-rings, and run a vernier over them.
The dimensions might be useful in the future, should the items go NFP/difficult to source.

part no ¦ Int.∅ parts listing ¦ int.∅ × thickness, measured
6460 CR ¦ 14 ¦ 14.0 × 1.80
6460 V0 ¦ 10.82 ¦ 10.8 × 1.80
6460 C2 ¦ not stated ¦ 8.75 × 1.80
6460 T9 ¦ 7.65 ¦ 7.60 × 1.80

All of these are used on a huge range of Citroen vehicles, right up to Aircross and Cactus.
Last edited by white exec on Sat Apr 24, 2021 10:01 am, edited 2 times in total.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

.
Conversion from R12 to R134a — Citroen documents

While browsing servicebox Parts for something quite unrelated, I found these four Service Documents.
They are detailed conversion instructions for converting from R12 to R134a — for AX, BX and CX.

By simply going into BX parts (not repair procedures, which I don't have a subscription for), and doing a Search for "blanking" (which is what I was looking for), you get this:
.
click to enlarge
AC conversion - Parts page, listing documents.JPG
.
The last four items are on-screen PDFs (which can be printed or saved), are are:
.
1 - Cleaning - air conditioning circuit
2 - Oil drainage - air conditioning compressor and dehydrator
3 - Conversion of air conditioning (up to RPO 3341)
4 - Conversion of air conditioning, single A/C, for RPO 3341→
.
The full documents are available to ServiceBox subscribers, via the page above.

EDIT
Don't get excited over this. There was/is obviously a bug in the SB system that intermittently allows some access to documentation, even when a subscription doesn't cover that. Most of the time, the site works normally.
Chris

UPDATE (June 2021)
The details in those four Citroen documents are now posted on FCF, in the Members' > Resources area of the forum.
Last edited by white exec on Sat May 01, 2021 10:07 pm, edited 6 times in total.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

BX etc Pressostat
Advice in the Cit documents is to replace with an updated one, because of the different operating temperatures of compressed R134a.

Original Cit pt.no. listed as 95 496 899, now NFP.
6455T2 replaces it, and is fitted to a string of PSA vehicles.

6455T2 also appears on Mister Auto - choice of half-a-dozen makes.
It's a triple pressure sensor. One spec reads:
<2 bar OFF [no gas]
>26 bar OFF [over-pressure]
17 bar ON [normal wkg pressure; replaces the earlier 19 bar]
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

Sanden SD-709 compressor — PAO and PAG oils

Having just completed (July 2021) the conversion from R12 to R134a on the BX's factory fitment here, I thought I'd add a couple of bits of information to the very helpful guide above. It relates to the use of PAO68 oil in the system.

As well as the dryer, pressostat and O-rings (and eventually the expansion valve as well), the compressor needed to be replaced, as the original one had a significant leak. I went for a Nissens 89171 (from Mister Auto), which is actually a Sanden SD-709, spec'd for R134a. Sanden was the OE fitment on the BX, and it appears that most (all?) of the aftermarket replacements for the BX are Sanden, just re-badged:
.
DSCF3903r.jpg
Sanden produce an excellent Service pdf for the compressors – see below.

The new compressor arrived with a clear warning that it was pre-filled with standard PAG46 oil, and that PAO oil should not be added:
.
DSCF3902r.jpg
.
Behr-Hella (Mahle) in their AC Compressor Oil pdf (below) make it clear that PAO and PAG oils are not completely miscible, and will separate out when left.
Even though the advice is to remove previous (PAG) oil from the system before switching to PAO, this is unlikely to be totally successful, and so a certain amount of mixing will happen.
Sanden are obviously not happy with significant mixing of the two oils, hence the yellow label, and the instruction in their Service document to use PAG46 oil.
I thought it worthwhile pointing this out.

There is also the issue of having a system topped up with refrigerant and the accompanying small amount of oil. AC workshops seem to standardise on PAG oil for R134a, and if the system is being run on PAO, the contents will only become more of a mixture.

https://www.sanden.com/productlibrary/m ... _Rev_2.pdf
https://www.hella.com/partnerworld/asse ... BHS_EN.pdf

Echoes of silicone brake fluid?
The chief stated advantage of PAO oil is that it is non-hygroscopic, where PAG is. Those of us with very long memories will recall the marketing of Silicone Brake Fluid in the '70s and after, which was also non-hygroscopic. It turned out to be far less lubricating than standard DOT3/4 fluid, and left many remote brake servos creaking and hesitant, with owners having to switch back to the DOT formulation.
I'm just wondering whether Sanden could have reservations about the performance of PAO, or remnants of it.

Re-gas quantity
Followed the Citroen conversion document, and used 85% of the original R12 800gm — so 680gm (700gm in practice) of R134a — along with PAG46.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by David »

This information is very useful. I couldn't find anything specific for the BX when I had mine filled up last week, so I went off a generic chart, which stated that it would need 606g of R134 when replacing 800g of R12.

I'll have to post the details of the compressor that I've used on here, as I too had to replace it. Only I used one that was for a Lamborghini Diablo. It bolted straight on the car & the only thing that I had to alter was the plug to power the clutch.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

Would be good to read about how you got on with yours.
The Sandens got fitted to lots of cars. One variable was the diameter of the driven pulley, to limit max comp revs.
On the BX, Citroen changed from a single cable feed to the compressor to a double one (+12 and Gnd), with a change of plug. The new Nissens/Sanden here was single cable, chassis Gnd.

AC BXs in the UK must be a tad rare. Not even that many in France, and even fewer in Spain. Maybe it was a comparatively high-cost option back then.
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by Jaba »

Something to bear in mind about charging is that the quantity of Rxxx refrigerant varies with the type of condenser fitted.
The copper tube based one fitted to the 16v and TD needed 800g of R12 and the folded aluminium one fitted to the others in the range needed 1000g as far as I remember.

They vary in physical size too, the copper one is smaller but as the thermal conductivity of aluminium and copper is different cooling performance is presumably the same.

I have had three BXs with a/c but never more than two at a time. I was going to convert a TD estate with a kit I acquired but the rust at the back end got to it first. R12 was deffo a better more efficient system than R134a
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Re: BX Air conditioning R134A conversion (all you need to know thread)

Post by white exec »

Wonder whether the copper condenser was dropped on cost grounds, or just superseded by the ali one? Most more recent cars use ali.
Using R134a requires its own TXV*, and it's possible many conversions (d.i.y. and trade) didn't include changing it. I originally intended to leave it alone here, but was obliged to replace it. Possible that the system cools less well with the incorrect valve.

* Replacement TXVs are labelled as either R12 or R134a, although Citroen's conversion document does not list it in the items that should be changed.

The refrigerant conversion documents (for AX/BX/CX) are available on FCF, in the Members' Area > Resources > Mechanic's booklets table. Donors to FCF have access to this area. There are BX Mechanic's workshop (Private Cars) booklets available there too. Downloadable and printable PDFs.
Chris