407 HDi Coupe AirCon oddity?

Graydog

Graydog

Member
Fellow Frogger
Joined
Jul 19, 2004
Messages
97
Location
Central Coast NSW
Sorry for what might be the dumb question of the day........something I've never experienced before. On two recent occasions on trips that were frequently on freeways (at 110kph) and on hot days, the A/C has really fallen away. The first trip was up to QLD in OCT...the A/C was quite cold when I hit the freeway at the Central Coast to Coffs. Next morning, not long after leaving Coffs on the motorway (and temp reaching 29/30°C) the cold air temp just dropped away? It functioned OK while we were tooling around the Gold Coast, then the weather was cooler on the return journey so the A/C wasn't 'stressed' and I wasn't as bothered about it.
Back home over the weeks since, no problems...until a trip to the Blue Mtns a week ago on a hot Sunday. All good and working OK until about when I hit the M7 and it dropped away again for the rest of the trip. Puzzlingly, it was OK on the way back. I typically leave the temp set at 18°C, but no amount of fiddling could give me the cold air on either occasion! I've got it booked for an A/C service + (probable) re-gas.....that may be the simple solution, but I'm puzzled about the circumstances described above. Anyone experienced something similar?
BTW: I'm on the prowl for a 2020 (or later) 508 Wagon to replace the ol' girl, so I need the A/C problem resolved either way.
 
Sounds like the evaporator is freezing up. Would you say that the failure is associated with more humid weather?

Check the drain hose under the car and make sure that it's not blocked. It's a favourite place for mud wasps to build their houses, and a buildup of moisture in the evaporator will cause it to freeze.

The second cause is a common fault, the evaporator temperature sensor can fail. This will prevent the system from disengaging the compressor when the evaporator temperature gets too low, causing the temperature to get below zero and subsequently humidity freezing to the evaporator.

From memory on a 407, you can get to the evaporator temperature sensor by removing the glovebox and some trim, and then standing on your head.
 
Don't forget to change the pollen filter!
 
Thanks Gents for those replies. A few quick responses to Dem's comments....
1. I couldn't specifically tie the events to humidity. I guess I am so acclimatised to humidity it doesn't quite register with me :unsure: The only common denominator I observed was the highway speeds....at suburban speeds things seemed OK?
2. Drain hose beneath the car is clear.
3. I'll mention the evaporator temperature sensor when I put the car in.
4. I take your point in the closing sentence re: standing on (my) head! Been there, done that - but for other tasks! :giggle:
 
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I've had roughly similar air con issues with two cars (Peugeot 306 and Subaru Forester). Problem was that on very hot days (well over 30), with the air con on, it would stop working after some time. Not exactly the symptoms you describe I admit.
In my case, it was excessive clearance on the clutch assembly. Easy fix was to remove a shim and everything has been fine since on both cars. Well worth checking the clearance as it is easy to do. You can also visually check if the compressor is spinning correctly and feel for the temperature difference between in and out lines when the problem occurs.
 
Can somebody tell me where to find the drain tube under the car . It sounds like it would be a good thing to check for blockage. Thanks in advance Keith
 
Drive your car around with A/C on for while. When you come home, stop the car and wait, look for the drips of water on the ground then look up.
 
If it's blocked then I expect your passenger would get drips on their feet - the water has to go somewhere!
 
I have been through this with my 06 407 v6. After rebuilding the compressor, getting a new BSI unit, we worked out that the compressor clutch connector wasn't connected as someone had probed it and opened up the connector so it wasn't connecting. Prised it back a bit and a/c working like a charm! Might be worth checking since it doesn't cost anything.

Also probably a good idea to hook the car up to Diagbox and see what errors are showing.
 
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