C4 coupe air coming out of any vents except when on highest setting

the fan speed resistor pack has failed, usual cause is that the pollen filter has not been changed as often as it should be. or may just be one of those things, some makes/models of cars are very prone.

Yeah common problem on many cars. My provious saab 9000 had same problem. Resistor pack just plugs in, but the original part can be expensive ~ £50. Some saabists were able to replace the power diode on the resistor pack. The pack depends on cooling from the fan blower. A low fan setting means highger resistor load; just when it's needs more cooling, doh!

Often the resistors are okay, it's just the associated thermal fuse that has blown. If you can get the pack out you can replace the fuse for a couple of quid.

Tim

Common problem also on Fords and it looks like that C4 has a similar circuit. On my car the module is actually part of to the cabin fan. On a friends French made car it was in the cabin air intake just below the cabin/pollen filter. More likely that the thermal fuse (which is part of the resistor pack) that has failed. The thermal fuse can be replaced on many units.

Ford example (written a few years ago)