C5 2001 - aircon not cooling drivers side

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aspire_helen
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C5 2001 - aircon not cooling drivers side

Post by aspire_helen »

First use of the aircon this summer, and I found the aircon has stopped cooling the driver’s side air (right side). The passenger side seems OK, but may not be as cool as before – not sure. The driver’s side will only blow ambient to hot air. The immediate thought is – faulty driver side temperature mixer/blender motor or flap broken/stuck/restricted etc. A common problem on C5 Mk2 s and Peugeot 407s. But that turned out NOT to be the problem........I removed the motor and checked both the motor and flap for full and free movement - all worked perfectly.

After a lot more investigation than proved necessary (doh!), I finally removed the temperature probe, low on the driver’s side, and ran my own digital temperature probe across the output face of the evaporator matrix, and found that the passenger side was 6degsC whereas the driver’s side was 19degsC ie ambient. Note – the aircon was set to 16degs both sides, with max fan, engine idling.

Before I delve deeper into other possible causes, has anyone experienced similar, and is this indicative of typical aircon circuit fault?? Eg re-gas needed or more serious? I have read that.....“BMW HVAC systems, by design, will preferentially cool the driver's side when the total system cooling capacity is compromised by low refrigerant. “ I wonder if Citroen is the same. As Citroen's heater unit is designed for left hand drive, the passenger side on UK models would be prioritised, as in my problem.

By the way, I gained access to the drivers side mixer/blender motor by cutting away a small piece of the dashboard under the steering wheel and removing a plastic tubular conduit in the dashboard. See photos. The pollen filter and inlet face of the evaporator matrix are clean and dry.
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Re: C5 2001 - aircon not cooling drivers side

Post by ozvtr »

aspire_helen wrote: 10 Jun 2022, 21:38 is this indicative of typical aircon circuit fault?? Eg re-gas needed
Yes. If there is not enough refrigerant, only the part of the evaporator closest to the outlet of the thermal expansion (TX) valve will get cold.
The evaporator has a (refrigerant) "in" side and an "out" side. The 'in' side is closest to the outlet of the TX valve. So the evaporator will get cold on the 'in' side, absorb the heat of the air passing through it and then be at ambient temp on the 'out' side. Normally the entire evaporator and the vapor line (going back to the compressor) will be cold. If that 'in' side is split out to one side of the car, well, that side gets the cold(ish) air.
Typically the TX valve will tend to hiss louder as the refrigerant level gets lower and the valve is now passing just gas instead of converting liquid into gas.
aspire_helen
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Re: C5 2001 - aircon not cooling drivers side

Post by aspire_helen »

ozvtr
Thanks for your quick response. I have booked in the car for a leak test and full recharge.
It is interesting that the system measures the vent outlet temperatures of the left (passenger) dash and feet, but measures the evaporator output on the right (drivers) side. Normally, the evaporator output would be the same across the matrix face, but I wonder if there is a design reason why the right side is measured, not left.
Currently, the evaporator output sensor will be returning ambient temperature. I wonder if that would cause the compressor to go into "over-drive" trying in vain to reduce the temperature !!
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Re: C5 2001 - aircon not cooling drivers side

Post by ozvtr »

aspire_helen wrote: 11 Jun 2022, 20:34 It is interesting that the system measures the vent outlet temperatures of the left (passenger) dash and feet, but measures the evaporator output on the right (drivers) side. Normally, the evaporator output would be the same across the matrix face, but I wonder if there is a design reason why the right side is measured, not left.
The sensor closest to the evaporator is really only looking for a "freezing" condition. So that the evaporator doesn't ice up and block the air flow. The second sensor allows the climate control unit to measure the rise in temperature from one point in the duct work to the cabin and "anticipate" how much cooling is required to get the cabin to the required temperature. This reduces over and under shoot of the temperature. My guess is the sensor is before the air is split out to the passenger side but it's on the passenger side?
aspire_helen wrote: 11 Jun 2022, 20:34 Currently, the evaporator output sensor will be returning ambient temperature. I wonder if that would cause the compressor to go into "over-drive" trying in vain to reduce the temperature !!
There must be just enough refrigerant/pressure in the 'high' side of the system for the engine ECU to allow the compressor to run. If the pressure falls below a certain point the engine ECU wont engage the compressor. There are variable displacement compressors that are electrically controlled to compress more or less refrigerant. This produces a more controlled and efficient way to cool the evaporator and therefor the cabin. I do not know if your car has one or not. If so, yes the climate control ECU will be requesting maximum displacement to try and make the evaporator colder. If not, the engine ECU will be requested to run the compressor for longer (or continuously).
The climate control ECU, the BSI and the engine ECU all have their part to play in the air conditioning/climate control system. But the engine ECU has the power of 'veto' to engage or disengage the compressor clutch!
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Re: C5 2001 - aircon not cooling drivers side - and rusted service ports

Post by aspire_helen »

Thanks for all the info. It is always nice to hear from experts in such technical detail. Unfortunately, my first problem is that the service ports are badly rusted . The caps do not protect the external surfaces of the ports....and who thought it a good idea to position them adjacent to the compressor, facing down (with caps able to collect water!) and only accessible from underneath with the under-body panel removed!? Moreover, the expanding rust had split one of the caps. Fortunately, the cap seals have successfully protected the internal M8x1 thread and valve which look fine. I have de-rusted and smoothed the external mating surfaces in the hope that the quick release couplings will still attach and seal when I take it the aircon garage this week.

A note of advice - check the condition of your ports, and add extra anti-corrosion protection to the external surfaces where the quick release couplings attach.
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ozvtr
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Re: C5 2001 - aircon not cooling drivers side

Post by ozvtr »

That's strange. The fixed lines are typically aluminium, but those lines are 'rusting' (oxide of iron). Are they steel lines ( I wouldn't think so)? Where is the iron oxide (rust) coming from?
I'm glad I don't have to deal with salting of the roads over here.
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Re: C5 2001 - aircon not cooling drivers side

Post by aspire_helen »

The service ports, and both the high and low side pipes connected to the compressor mounted on the engine, are steel. The pipes attached to the bodywork are aluminium, with the usual flexible hoses joining the two. So, why did Citroen not locate the service ports on the more accessible, and better protected, aluminium pipes?!!! ....or use caps which protected the external mating faces (standard high and low port valve caps do not). Doh.

I de-rusted the ports but they were too pitted for the r134a quick connectors to latch and seal. So, it is impossible to re-gas, or even de-gas. I am exploring options to repair, replace or relocate the ports - I have a plan to utilise thread couplers and r12 / r134a adapters....possibly without even de-gassing. If successful I will post.
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Re: C5 2001 - aircon not cooling drivers side - UPDATE- and now No cooling!

Post by aspire_helen »

I finally manufactured an adapter to enable a quick connect QC coupling to seal on the rusty Low side. I will post that in the Aircon topic, but here is photo of both new adapters fitted to the existing service ports.
New R134a service ports fitted to rusted original ports - original valves untouched.
New R134a service ports fitted to rusted original ports - original valves untouched.
I was expecting the Low side pressure to be very low ie low refrigerant, but it measured 65psi at 23degsC, so is evidently not leaking. I have to confess that the aircon system has not been touched since new ie 21 years!
Low side static pressure
Low side static pressure
With the aircon running at max, it read about 30psi. Moreover, the condition has now worsened to virtually no cooling on either side and a gurgling noise coming from the centre vents. On engine shutdown, the Low dropped to 60psi before equalising to the previous static 65psi.
I intend to take it for a full vacuum pump out and re-fill. Any ideas?
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Re: C5 2001 - aircon not cooling drivers side

Post by GiveMeABreak »

That's what I would do - get a full A/C service. They should be able to vacuum out the entire system, undertake a pressure / leak test and then clean and disinfect it before refilling with the correct amounts of gas and oil where applicable. I paid a mobile A/C technician with all the kit on board to do this at home for £80! Well pleased with the results.

It had been to ATS a year ago for a recharge, so that failed and they over-filled it! They read the wrong amounts of their "chart". I won't be going back there needless to say, and will be using the mobile chap again in future.
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Re: C5 2001 - aircon not cooling drivers side

Post by ozvtr »

65 psi static pressure and the "gurgling" sound tell me the system is low on charge. The gurgling is a mixture of liquid and vapor on the high side going through the TX valve. It should all be liquid.
aspire_helen wrote: 25 Jul 2022, 21:08 I have to confess that the aircon system has not been touched since new ie 21 years!
If it has taken 21 years to get to this stage, while obviously leaking, the leak rate would be too low to detect and it would be considered acceptable.
However, if it has suddenly lost it's cooling ability over a short period of time, a bigger leak might be the case.
Finding big leaks is easy, finding small leaks is a pain!
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Re: C5 2001 - aircon not cooling drivers side

Post by aspire_helen »

I agree with you, Marc. I initially took the car to Kwikfit, but they treated me like an idiot, so I took the car away, and on to Halfords. I had a long chat with the manager who was most amenable to my involvement. So, they got the job. They removed (only) 100g of refrigerant (vice 600-650g), and vacuum tested it with no leak over 45mins. I was keen to ensure they refilled it in accordance with the Citroen mechanics handbook (doc ref CAR050007) specifications for my Sanden SD7V16 which was 600-650g of R134a and 135cc of PAG46 (vice SP10). Some references on line do not cover the 11/2000on 2.2Hdi. Fortunately, Halfords' reference was the same as Citroens. Oh , joy.......4.5degsC ! It cost more than expected, £90ish, but I was willing to pay extra for a mechanic that did not patronise me. Best thing....my R134a service port repair adapters worked a treat. I made a change to the earlier photograph....I replaced the fibre washers with 2mm aluminium sealing washers....hence final photo below. As the original Schrader valves remain in place in the old ports, the adapters can be removed.
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R134a service port adapters to repair rusted originals
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Re: C5 2001 - aircon not cooling drivers side

Post by GiveMeABreak »

Excellent - very pleased you are now 😎 again!
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