identifying relays

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sdelasal
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identifying relays

Post by sdelasal » Sun Sep 21, 2014 11:20 pm

My BX, 1.9D, has A/C and twin rad fans. The fans are not working correctly and i'm trying to figure out the wiring - I've looked at the various threads on the subject in the archives but the question I have is as follows. In the scuttle, under the NSF windscreen, I have a row of 4 relays + one spare. Can anyone identify what these are - left to right? I can't find any reference to them in haynes or snippets I have from the citroen files. Steve
Last edited by sdelasal on Mon Sep 22, 2014 6:52 am, edited 1 time in total.

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Way2go
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Re: identifying relays

Post by Way2go » Mon Sep 22, 2014 2:08 am

My A/C system awaits recharging so I cannot verify the order of the relays but IIRC the operation of the relays is as follows :) :

One relay overrides the first over-temperature output of the radiator switch and is triggered by sliding the cabin temperature switch off its stop. (This works even if the system is out of gas.)

A second relay overrides the second over-temperature output of the radiator switch to bring In both fans and is triggered by the high gas pressure switch in the system.

I believe the other two relays operate in conjunction to control the A/C system, one not allowing the clutch to be engaged If the low pressure switch is not true, the second controlling the duty cycle of the clutch based upon the position of the slider in the cabin and hence the intensity of the cold air.

I also seem to remember that some folk have had problems when recharging with R132a that the lower gas pressure does not trigger the low gas sensor and as a result they short it out to gain operation. The compressor would be at risk now if the system charge failed. :shock:
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mat_fenwick
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Re: identifying relays

Post by mat_fenwick » Mon Sep 22, 2014 10:20 pm

I can't be certain of the order of the relays, as I fitted the system myself and am not sure I put them on in the same order they came off the donor car. whilst trying to get my head around the system, I drew up some rough schematics with current flow superimposed on them, which may help?

Image

Image

I can email you the complete wiring diagram I have for the AC system, but I've heard there are several variations on it.
Image

1993 1.9 TZD Turbo Estate
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sdelasal
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Re: identifying relays

Post by sdelasal » Tue Sep 23, 2014 8:23 pm

please do Mat, i'll pm you.