More aircon problems

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Jaba
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More aircon problems

Post by Jaba » Sun May 21, 2006 9:59 pm

My aircon is playing up too.

It seems to work normally for up to the first hour and then the air temperature at the vents quickly rises to ambient temperature or close to it anyway.

My brief checks when it is failing show that the compressor remains in circuit and is turning continually but the temperature of the refrigerant pipe into the condensor is the same as the exit pipe. So the compressor keeps pumping because the evaporator temperature never drops and is always at ambient.

When it is working initially then the compressor cuts in and out as normal.

Any of you experts know what might be going on here ??
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velosolex50
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Post by velosolex50 » Sun May 21, 2006 11:17 pm

Hi
Are the condensor fans blowing when it stops working? If they are not you may just be geting compressed gas out of the condensor instead of liquefied gas, so no liquid to evaporate in evaporator, & no cooling of your vent air. No doubt the proper experts will be in with ideas shortly.
Good luck
Huw

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Post by AlanS » Mon May 22, 2006 1:41 am

Sounds as though you are icing up the evaporator.
If you're trying to run the system with the air vent open it will happen all the time. On BXs, it is essential that the air vent is set on recirculate. I know the Xantia can operate on fresh air supply, but the Xantia also has the later style of system that can do this, the BX isn't and will choke on the frozen condensation which will in fact cause ice to pack around the sensor and keep it at a temp that is within its operating range whilst the ice will continue to pack on the coils of the evap which is why the discharge line also feels normal temp as there's no load passing over the coil because it's packed with ice. Switched off for say half an hour, pool of water under the car, switched back on all works as normal again???
Easy fix, either close off the vents or find out where the air is leaking into the cabin or coil area and causing the iuce build up on the coil.


Alan S
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Post by ernst stavro blofeld » Mon May 22, 2006 8:51 am

Sounds spot on to me Alan. This is why those intending to retrofit aircon are strongly counselled to fit the recirculating kit! Incidentally, the system fitted to my own BX with your considerable help has been in for two years now and still works beautifully; many Thanks.

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Post by Jaba » Mon May 22, 2006 11:42 am

Thanks guys. I had worked out some of this already, so I only use recirculation - but it still fails within the first hour. I do get a pool of water when I stop the car, but not always.

It seems to me that it is icing up when it should not be. My other BX with a/c does not fail in this way and I do not get the pool of water either.

So either I have an air leak/bypass from the recirculate air flaps or is the thermistor or its circuitry playing up ??

I am still a bit puzzled by this though. The thermistor, in failing condition sticks on - the compressor and fans run all the time the fans are running at LOW speed but there is no refrigeration taking place its just pumping presumably gas and oil. If the sensor becomes ice bound would it not then be too cold to still want keep the compressor running. What is it for if not to regulate the temperature of the evaporator.

I am not disagreeing in any way with you guys - But there is more going wrong than just the position of the airflaps.
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Post by AlanS » Mon May 22, 2006 11:56 am

The temperature is obtained by air passing over the fins and pipes of the coil (evaporater) but as soon as it ices, it is no longer acting as an air/con should, but is in fact trying to keep a bit of ice frozen. Water freezes at 0 deg C and once frozen solid, that is as far as it is ever going to get, as a result, it loses its load and as a result will lose the heat on the discharge side as it is no longer drawing heat from the coil. Ice is an insulator in its own right, so it will just keep the temp at a levelthat will allow it to keep on running without either getting colder or turning the compressor off.
If "gas and oil are circulating" then the system should be operating unless the load has been removed as an iced coil will do. Another reason it will not be heating is that once it is iced, then the lack of load causes the refrigerant to "pump down" and leave the majority of the gas in the sump as the T/X will not be operating normally due again to the lack of load.
I recently had a call from another member and his BX had the T/X valve cover missing. He had knocked up another and has noticed a large difference in the efficiency of the system.
If anyone has ever had the fans off and stuffed up putting them back, it may not be recirculating the ait which is another cause of icing and lack of efficiency but my guess is either a problem with ambient air getting in, the t/X cover missing (accessible once the glovebox is out) or maybe even a partial blockage of the drain.


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Post by Jaba » Tue Jun 13, 2006 8:42 am

I now have this car back in UK and have had a good look at the A/C.

Here is a typical failing scenario. Temperature in car 45 -then with a sensor in the airflow and ac on the temperature quickly goes down to 9-10 degrees (too high ?). Drive for half an hour temp in car around 30 + in vents it gradually drifts up to 14-15 degrees.
Park up for 30 mins. Temp in car 40 degs. on return drive back and no cooling - temp in vents 25 degs. but the compressor is on and there is no heat coming in the condenser.

The next day it is back to working again - it seems that the hotter the ambient temperature the less it likes it.

I can now definitely say that it is NOT icing up - it is just not cooling properly all the time. Another clue is that when I switch the engine off there is a noise from the evaporator that sounds a bit like a kettle switched off just before it boils.

The expansion valve cover is in place and there is a tiny amount of oil on the valve.

My other BX does not make this noise and also cools the air down to 2-4 degrees.

I am reluctant to take it to a specialist with these symptoms as I know that they will want to do the R134a conversion first and they wont cure the problem.

So any further ideas. I think it might be the TX valve not opening fully, partially blocked or just faulty.
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Post by tom » Tue Jun 13, 2006 9:03 am

Oil on the valve will be part of the problem. That will be causing a loss of gas. The cost of a proper conversion is worth it because you'll need to remove the valve from the evap. to stop it from leaking.

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Post by Mr B » Tue Jun 13, 2006 12:30 pm

Jaba wrote:when I switch the engine off there is a noise from the evaporator that sounds a bit like a kettle switched off just before it boils.
Mine makes this noise too, what does it point to? Mine cools fine though :roll:
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Post by RichardW » Tue Jun 13, 2006 1:41 pm

Dunno, but you can hear it on my Xantia when the A/C is running now I've put some more gas in it - needs more yet though. I'm ignoring it.....
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