Aircon electrical problem

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aneesh84
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Aircon electrical problem

Post by aneesh84 » 09 Aug 2011, 12:33

I am Aneesh from Portugal. I own a Citroen Xantia 1.9 TD (1994). Recently my AC compressor stopped working. I refilled the gas into the system but still have the same problem. I thought maybe the pressure switch is defective, and replaced it with one from a friend's car, but it still doesnt work.

To check things further I bought a multimeter today and checked all the contacts of the pressure switch.

My understanding of the pressure switch goes as follows. Please correct me if I am wrong. Contacts 1 and 2 should form the compressor clutch activation circuit while 3 and 4 should form the fan high speed switch. So, under normal conditions, contacts 1 and 3 should be supplied with 12 V DC. Under normal operations, the pressure switch contacts 1 and 2 should be normally closed and contacts 3 and 4 should be normally open.

Test Results

Now only the pin wire 3 has 12 V supply. Hence 1 is not receiving 12 V supply. seems like maybe some sensor somewhere is cutting of supply to pin 1. So i think it should not be a relay problem. Could you suggest what sensors are connected in series before the supply reaches pin 1.

Also, when pin 3 and 4 are connected, the fan does not start spinning in high speed. I guess this is another problem, but more related to safety than functionality.
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Post by addo » 09 Aug 2011, 12:58

Have you checked the gas pressures with the engine running and aircon switch on, using some pressure gauges?

Also test the compressor clutch by disconnecting the plug and jumping with 12V and earth direct to the compressor for half a second.
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aneesh84
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Post by aneesh84 » 09 Aug 2011, 13:07

The pressure switch is working normal, with contacts 1 and 2 as closed conn ections just as it should be. So i pressume it should not be a pressure problem. The problem is that contact 1 at the pressure switch is not receiving 12 V power supply, so it is not able to supply power to contact 2.

However contact 3 is receiving power supply. When i short contacts 2 and 3, the compressor works as normal and the cooling levels are also good.

Also when the AC switch on dashboard is pressed, the radiator fans start working at normal speed so its also not a problem with the AC switch.
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Post by addo » 09 Aug 2011, 13:19

Pin 3 always receives 12V as it feeds from F2. At 17 and 26 bar it allows 12V to Pin 4, which triggers the Bitron to operate fans.

At 2.6 bar and less, it doesn't. I think this is because 2.6 bar is considered inadequate gas pressure for successful AC operation.

Pin 1 connects to Pin 2 (this pin ultimately switches on the compressor) at 2.6 and 17 bar only. so, by sending 12V (pin 3 to the clutch (via pin 2) you have proved one of the relays (violet socket) is fine!

I would suggest that possibly either the other aircon relay (black socket), Bitron or A/C ECU is faulty. The reason I can't suggest one or the other of these two controllers is I'm not sure which one supplies the signal and which responds. Check this relay first anyhow.
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aneesh84
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Post by aneesh84 » 09 Aug 2011, 16:08

addo wrote:Pin 3 always receives 12V as it feeds from F2. At 17 and 26 bar it allows 12V to Pin 4, which triggers the Bitron to operate fans.

At 2.6 bar and less, it doesn't. I think this is because 2.6 bar is considered inadequate gas pressure for successful AC operation.

Pin 1 connects to Pin 2 (this pin ultimately switches on the compressor) at 2.6 and 17 bar only. so, by sending 12V (pin 3 to the clutch (via pin 2) you have proved one of the relays (violet socket) is fine!

I would suggest that possibly either the other aircon relay (black socket), Bitron or A/C ECU is faulty. The reason I can't suggest one or the other of these two controllers is I'm not sure which one supplies the signal and which responds. Check this relay first anyhow.


Thank you addo. Can you please tell me where exactly is the aircon relay. Is it on the driver's side, behind the fuse box. Can you tell me how i can spot it.

Thank you
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Post by addo » 10 Aug 2011, 00:26

It is probably in the fusebox located to the left side (when viewed from behind) under your "capot". I have a Ph.2 car, where the layout is slightly different.
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Post by aneesh84 » 10 Aug 2011, 01:12

addo wrote:It is probably in the fusebox located to the left side (when viewed from behind) under your "capot". I have a Ph.2 car, where the layout is slightly different.


Today I checked all the relays i could find both under the dashboard and under the bonnet. All of the relays except one orange relay located behind the fusebox under the steering wheel, are working. Do you think it could be the orange one?

I just took off all relays one by one and applied voltage to check them.

I pressume you are referring to relay 8015 in this circuit diagram?

http://www.eastment.net/xanwd/mk2achv.jpg

Also one more question, is 8010 (Refrigeration coolant temerature control unit according to haynes) the same as the bitron or is it somehing else?

By the way, 8007 is the pressostat and 8020 is the compressor clutch.
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Post by addo » 10 Aug 2011, 05:04

Yes, you correctly identified the Bitron unit as 8010.

The other relay I mentioned is 8015. The way to positively identify this one, is to look at the numbers on its feed wires; at least three of them should start with 807.

Rather than checking the relay itself works, you need to look for supply voltage at the wire C020, and a ground conductance when engine running and AC switch pressed on, for wire 8075.
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Post by Clogzz » 10 Aug 2011, 16:27

Maps of the Mk I air conditioning with mentions of aircon stop relay, violet relay and pressure switch.

Image Image Image Image
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2003 C5 2.0i AL4 183,000 km 76372389