Aircon only temporarily cold

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Agour
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Aircon only temporarily cold

Post by Agour »

Hi all,

Been having an aircon issue with my m2 citroen c5 estate.

Sometimes (not every time) I start the car, it comes on cold for a few minutes, then tails off and becomes ambient temperature air. That said when it was blowing cold, I don't think it was as cold as it had been in the past.

I took it to get regassed, and the man at qwik fit said that if its blowing cold at all, I probably have some other issue. So we didn't bother with the regas.

It has been about 2 years since the last regas, so I'm thinking maybe the system is just low on gas and the remnants are settling in the system when the car is off.. hence why I get a blast of cold-ish air for a few minutes? I figured I would ask on here first before commiting to the regas, as funds are tight right now.

However my temperature sensor has been a bit wild recently. It was reading -15 when outside temp was about 7c. It has been normal a few times (and made no difference to the aircon), so I'm guessing these issues are unrelated.

Any thoughts?

Thanks,
Paul

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GiveMeABreak
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Re: Aircon only temporarily cold

Post by GiveMeABreak »

The outside temperature sensor (as displayed in the vehicle) is located in the wing mirror and has nothing to do is used with the other systems so do get this replaced first.

As for your A/C - leaving it low on gas for any period of time and certainly 2 years is bad for the seals in the A/C system. It is why we recommend operating the A/C at least once a month as a minimum to ensure the seals maintain their integrity. If there is a leak in the system, air will enter and the system seals will rapidly deteriorate.

If the A/C is low on gas, the compressor will be shut off automatically to prevent damage to the compressor. You can check this by getting another person to switch on the A/C to ON (or AUTO if you have climate control) whilst you check under the bonnet and see if a) the fan comes on at slow speed, which it will of the A/C is working, and b) you should be able to see the clutch engage on the compressor, making a clicking noise as it energises. Switching the A/C off will stop the fan (as long as the engine isn't hot and the engine has been running for ages) and you will see compressor clutch is engaged. Getting somebody to engage and disengage the A/C while you are watching will tell you if the compressor is running or not.

If it isn't engaging, then the system is either low on refrigerant and / or there is a leak in the system. The most common issues are a stone chip hitting the condenser radiator (the small radiator that sites next tot he main engine radiator. These are particularly vulnerable to getting hit by stone chips and other debris.

So the only way is to get it leak tested - where they will charge the system up with fluorescent dye, operate the system for a while and then look for traced of dye to determine if and where there is a leak.

Agour
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Re: Aircon only temporarily cold

Post by Agour »

That's awesome, thanks for the very indepth reply Marc!

I have always had the AC switched on, even in winter. So hopefully shouldn't be an issue with the seals :)

Just ran it now and the compressor is definitely engaging and disengaging (whilst car still pumps out cold-ish air).

I'll pay to get it regassed, at least then when they pressure test it I should have a decent idea if it's OK or not.

Thanks for the help!
Paul

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GiveMeABreak
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Re: Aircon only temporarily cold

Post by GiveMeABreak »

No problem, Kwik Fit do a 'Recharge or No Charge' if they don't cool it by more than 10°C from the coolest vent in the car. The fact that it is engaging is good - but switch it off now until it is gassed up again.

wheeler
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Re: Aircon only temporarily cold

Post by wheeler »

GiveMeABreak wrote:
23 Mar 2020, 13:54
The outside temperature sensor (as displayed in the vehicle) is located in the wing mirror and has nothing to do with any other system.
That's actually incorrect, the outside temperature sensor most certainly does have have an input (via the comfort CAN) to the AC system on the C5. A faulty external temp sensor can affect the AC operation.
The mk1 C5 was notorious for external temp sensor failures & also caused A/C issues.
I'm not saying this is what's causing your fault but I would definitely replace it before attempting to diagnose any further.

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GiveMeABreak
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Re: Aircon only temporarily cold

Post by GiveMeABreak »

Apologies - Wheeler is correct - I was obviously on another planet at the time. The exterior temperature sensor is used in the A/C system so yes, do get the sensor replaced first as it could be affecting the operation if it thinks it is a lot cooler than it actually is! I'll correct my last post on that to avoid future confusion.

Agour
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Re: Aircon only temporarily cold

Post by Agour »

Ah ha!

I didn't get notifications of the older replies, so hadn't seen what you said.

I recently got my AC topped up, and was working fine for a week or so. Today on an hour drive the car temperature sensor read minus 39C, and the air con didn't work.

On the way home the temperature sensor the correct outside temp, and low and behold the air con worked...

I know it's in the wing mirror in the black plastic shroud. Any tips on pulling the black plastic off?

Agour
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Re: Aircon only temporarily cold

Post by Agour »

Swapped my temperature sensor over tonight.

For anyone who wants to remove the sensor on a mk3 c5 with folding mirrors, as it took me a little while to figure out:

Remove the mirror by carefully prising it out with a screwdriver.
This then reveals two clips for the painted section, unclip these.
Then carefully prize the coloured section off with a flat head screwdriver.
Lower black section is then revealed which can be clipped off with the now obvious clips.