Fiesta air-con switches off

[bitey]

When the engine switches off with start/stop - the air-con also seems to switch off - the fan speed is unchanged but the air is not being cooled.

When engine restarts - the air-con is back in business.

I don't think this is how it should be and is frustrating in this weather - is there a fix?

 

 

[Tiexen]

I don't think it has enough power to run the a/c without the engine, if it does turn off it must think the temp inside the cabin is OK - it should restart if needs to run the a/c

[jsk]

I am sure I read somewhere that with air con running the stop/start mode was inoperative. ie air con running engine won't automatically turn off when stationary and out of gear.

[MJNewton]

Generally speaking that's right, if the aircon is explicitly required to be actively operating (or the heater matrix for that matter) then the engine will remain running or be restarted. There can however be sufficient residual cooling/heating capacity in a stopped engine and so this won't always necessarily occur though.

In these recent hot temperatures (~30C for the sake of anyone reading this in the archive!) I have found my start-stop to rarely function. This is either down to the full aircon capacity being required but could also be that the function doesn't operate at all when above 30C due to the engine's own cooling system being required to remain fully operative.

[bitey]

The stop/start works fine on my 2017 Fiesta EcoBoost with air-con on full blast (it's just the cooling that ceases along with the engine).

 

 

[martin2345uk]

I have climate control on all the time and the start stop hasn't worked since I bought the car couple weeks ago, I assumed that was the reason [emoji52]

[kingsblue]

The air con pump is run off the aux belt, without the engine running the pump isn't being driven.

[MJNewton]

The evaporator does have thermal inertia though and so can still provide cooling capacity for a period without the compressor running. This actually happens regularly as the evaporator could eventually  ice up if the compressor were to be run continuously. 

[bitey]

That's interesting particularly Kingsblue and MJNewton - however this from Ford UK:

Quote

When you stop at traffic lights or your car is idling in a queue, this technology can automatically switch off the engine while still supplying power to essentials like the headlights, air-conditioning, radio and the Ford SYNC system. When you're ready to move, just depress the clutch and select first gear as usual, or press the accelerator on an automatic, and the system restarts. Auto-Start-Stop is particularly effective in towns and cities, where it can cut fuel consumption by up to 10% 

 

[MJNewton]

That aligns with what we're saying but it's not going to go in to the nuances of when it will and won't operate (the manual gives a bit more information in this regard such as min (0c) and max (30c) temperatures, battery charge level etc).