The air con on my 2015 focus is only working through left hand vents (not as cold as it should be either). It's happened a few times now. My dealer says that this happens when the refrigerant gets low through leakage. Is this correct or am I being fobbed off?

The first time it went in they told me they were fitting a heater control unit and I kinda suspect that this is still the fault. They haven't been able to find any leaks in the system.

...So, is it right that air con only works on one side when it's needing re-gassing. Need definitive answer so I can challenge the dealer.

 

TIA Chris

Yes it can happen, my manual controlled heating/air con did this not long ago . I had 245g of refrigerant left so only got cold on left vents. I regassed it with the correct amount( think it was 570g ) and it works perfectly through both vents now. If you have dual climate control the temp difference  can be affected by faulty sensor