Fitting air conditioning in an old diesel BX

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mat_fenwick
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Post by mat_fenwick »

rmattila wrote:what information drives the compressor clutch? I would guess there's a pressure switch somewhere..?
Yes, but it gets a little more complicated than that...

The logic is like this:
Engine normal temperature, A/C off - no fans
Engine normal temperature, A/C on - both fans slow
Engine hot, A/C off - both fans slow
Engine hot, A/C on - both fans slow
Engine very hot, and/or A/C high pressure - both fans fast

Jaba has previously posted up the A/C wiring diagram, although there are apparently a number of variations on this:

Image

These sketches are a simplified outline of the current flow for the radiator/evaporator fans, if they are legible!

Engine Hot
Image

Engine Very Hot
Image

(I drew them up while I was having some problems with the cooling system).
Last edited by mat_fenwick on Wed Jul 13, 2011 3:06 pm, edited 1 time in total.
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Post by Defender110 »

rmattila wrote:
Jaba wrote:You can see a pic of a sump showing the compressor mounting lugs here:
http://cgi.ebay.co.uk/Citroën-BX-16v-Pe ... 3a67d17c9f
Thanks, that clarifies a lot. Does not seem impossible to weld the necessary fittings and supports to an ordinary sump.
I think you would need to beef it up considerably, looking at how strong that alloy sump looks. Citroen aren't renown for over engineering so I assume there must be a lot of strain on the compressor when it kicks in & out.
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Post by Philip Chidlow »

As a matter of considerable interest: how long to change a compressor?
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Post by rmattila »

Defender110 wrote:I think you would need to beef it up considerably, looking at how strong that alloy sump looks. Citroën aren't renown for over engineering so I assume there must be a lot of strain on the compressor when it kicks in & out.
Yes, I think so too. But there's plenty of room around the sump to weld the support structures, so I think it's doable anyhow.
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Post by mat_fenwick »

Philip Chidlow wrote:As a matter of considerable interest: how long to change a compressor?
Actually physically changing it - under an hour. So if you include the pump out and re-gas, I'd guess around 2 hours total. That is of course assuming that the fixing bolts come out OK (the top 2 are awkward to access without a ratchet spanner).
It may be a good idea to inspect the condition of the mounting bushes on the sump at the same time - mine had softened from oil contamination to the extent that they allowed the compressor to run out of line. Citroen were no use for replacements, so I made my own from fuel pipe drilled out to suit the original steel sleeves.
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Post by Philip Chidlow »

Thanks for the tip... :)
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Post by rmattila »

Got the reply from the guy who I got the parts from.

My initial hunch was correct:
Is an extra pulley fixed on top of the alternator one or what..?
That's how he said it was done in the BX he removed the parts from. So the extra pulley goes to the crankshaft end on top of the poly-v pulley turning the alternator belt, and the alternator belt remains untouched. The extra long bolt for fixing the pulley is included in the pile of bits I got. 8)
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Post by Jaba »

rmattila wrote:Got the reply from the guy who I got the parts from.
So the extra pulley goes to the crankshaft end on top of the poly-v pulley turning the alternator belt, and the alternator belt remains untouched.
OK that makes sense and will work obviously. Your biggest problem still remains though. Wiring it up and then seeing if you have any leaks. Unless you know that it was a working system before it was stripped.

It might be worth plumbing it all up together with new orings off the car before installing it and getting it leak tested. That way you will know that the condensor and evaporator are 100% and have no damage as well as the rest of the system.
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Post by rmattila »

Also got a couple of pics of another BX A/C installation, where the compressor is fixed to a steel bar fitted under the bolts of a regular tin sump:

Image
Image

So this thing is slowly starting to make some sense after all.. :P

Noted what you said about leakage testing the system prior to installation - certainly worth considering. Have no idea of the design pressure though, but that should be easy to find out.
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Post by Defender110 »

rmattila wrote: So this thing is slowly starting to make some sense after all.. :P
Apart from like you said ; why you want to fit it to a BX in cold Finland :?: Do we have some long distance journeys planned :?: :wink:
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