Citroen C5 (X7) auxiliary heater

[Repmojer]

The main fans will only work when the engine is running, it requires a pre determined battery voltage to run them which you only get with the engine running.

Peter

Either way there are something that drives the circulation and making warm air blow out from the openings and that is spreading the heat to the windscreen and the cabin, and that wasn't working before I swapped the Battery Charge Status Unit.
There might be an auxiliary pump or something that drives the circulation of coolant? Also, I might be misremembering but I'm pretty sure every car can have cabin fans running without having the engine on?!

[wheeler]

The majority of Citroen & Peugeot models require the engine to be running for the interior fans to operate. In my opinion all cars should be like this to stop the battery being rapidly discharged by the fans. Pretty pointless to run the fans without the engine running anyway as there will be no coolant circulating so after a few minutes no (meaningful) heat anyway, same for A/C, only works with engine running so no proper cooling.

[Peter.N.]

I thought the aux heating was done by an electric element which is why it comes up so quickly and why it has such a large alternator. Also why the heat comes up when the engine is stone cold.

Peter