C4 Heater/AC not working

[snawheed]

If i bridge connection from resistor and it works whats at fault??

[Paul-R]

If you bridge the control unit (resistor) and the motor doesn't work then it could be a fuse, faulty wire/connection or the motor itself at fault. Or any combination of those. And the control unit hasn't been ruled out by that test either.

If the motor works and then when the control unit is reconnected continues working properly then it could be the motor putting an extra load on the control unit (due to "stiction" after being left unused for a while) causing the control unit to register a fault and close down. It's also possible that the control unit has become too fussy about the load it can handle.

If the motor works and then when the control unit is reconnected doesn't work then it could be either the motor or the control unit. Or both.

[snawheed]

Iv changed motor, controls and resistor still nowt so going to try an bridge it

[Paul-R]

I'm assuming that the control unit is the same or similar to the one in the X7. You could rule out a faulty earth connection by, instead of bridging the Black and Green/Yellow wires, connecting the black wire directly to a good earth and then starting up the engine.

[snawheed]

Il give it go again later, of nothing al try and purchase another fusebox, everything else has been replaced lol

[Paul-R]

Be careful with replacement fuseboxes (I think the correct term is BSM). Again, assuming this is the same as the X7, there are many different types and they are not interchangeable.

[snawheed]

Im going to check part no. before i buy

[snawheed]

Looking to replace fuse box under bonnet which no. do i go by or is it both?

[Paul-R]

I really think you're jumping the gun on this. If it were me I would be tracing the live feed to the motor back to the fusebox first.

Have you tried the wire jump yet?

[snawheed]

Looked at it but ive no green/white wire
Mine has red, 2 black and a thin white wire

[Paul-R]

I was hoping the colours would be the same as the X7. I suspect that the green/yellow wire on mine is black on yours but the clincher is the fact that these two wires are much thicker than the other two. It's the two thick wires that need bridging.

To check the actual earth connection you could run a wire from the bridging wire on the plug to a good earth point.

[petef]

The 'bridge' referred to is detailed in the post I originally started here https://www.frenchcarforum.co.uk/forum/ ... 4&start=30.
I am attaching a photo of the bridge wiring above the under bonnet fusebox - the BSM, which was done by a local auto electrician. Everything then worked fine, but eventually, I decided to replace the BSM itself. Basically I wasn't happy with the potential strain on the ignition switch - if the heater blower was on when the ignition was turned off it would come back on straight away when the ignition was turned on again, instead of kicking in when the BSM relay operated after the engine was started. All I had to do after installing the new BSM was remove the fuse from the bridge.
As Paul says, make sure you get the correct BSM, the original one on I got on ebay was nearly right - except you couldn't turn off the wipers.......

[Paul-R]

Ah, that's not the same bridge as I was talking about although it's very interesting and possibly worth investigating.

The bridge I was talking about is across the plug that connects to the control unit.

[snawheed]

Got car back from auto electrician, its the under bonnet fusebox

[Paul-R]

Have they just diagnosed it or has it also been fixed/replaced?