C4 interior blower not operating

don

don

Active member
Fellow Frogger
Joined
Oct 23, 2004
Messages
533
Location
Mayfield Newcastle
Morning all
2008 C4 sx multi zone aircon blower not working
Everything on the panel indicates working and AC compressor runs but no blower motor

Where should I start the problem solving please
 
There is usually a controller box between the aircon controller and the blower motor.

Usually the brushes on the motor wear down until they start to spark excessively, and that destroys the electronics in the controller. So new controller required and new brushes in the blower motor.

Cheers, Ken
 
The blower fan draws a lot of current and puts stress on every part of the electrical chain, from the battery to the fan motor. I have seen nearly every part of the fan circuit fail (in different cars).
The usual suspects are the fan motor, the fan speed controller, the BSI fuse holder and the relay in the BSI. It could also be melted connectors.:(
First point of call is the fuse in the BSI (under bonnet fuse box). Prey that it's that! If not...
You will need a multi meter to check for power. With the relevant controls on, start at the blower fan connector and check for power. Work back to the electronic controller (or resistor pack if the controller is not electronic). If the fan controller is NOT electronic I.E. a resistor pack, the next stop is the control panel fan switch. After the control panel, the next stop is the BSI. If the fan controller IS electronic the next stop is the BSI (after the controller).
Take note of the colours of the power wires. You will find the power wires are larger than the other wires.
If you track it down to the BSI and no other electrical devices in your car have failed you WILL have power at the fuse. At this point the failure is in the BSI and it will need to be replaced. The BSI's in the C4's are potted with RTV and virtually impossible to repair!
If your C4 has an electronic fan controller (digital controls), I would look for power there first. Of all the likely suspects, the electronic fan controller is the most likely.
 
Some of those C4s had a fan resistor unit with a soldered joint that would let go. It was a form of overheat safety I guess.
 
D'oh! Not the BSI, the the BSM! Sorry, the BSI is the fuse box in the glove box and the BSM is the fusebox in the engine bay. The power for the fan comes from the BSM in the engine bay. :mallet:
 
Thanks for the update fellow froggers, it has finally stopped raining so Ill get out and under. will update this thread as we go along
 
Ok so pulled the fan brushes worn but fan works OK.
Bearings quite stiff so hit them with some lube, much better but this little fan sucks some amps !!!!
the front panel is the digital type and my meter indicates 13.9Volts initially when the fan is turned on and increases on up to 14.3 volts.
So Im moving to the MSI have I got that right ?
 
Don,

I am presuming you measured no volts on the fan motor wires. If so,
I would follow the wires from the fan back to the fan controller box and see if you can see some volts there. There should be power and earth and a control voltage which varies as you change the fan speed control.

Cheers, Ken
 
don said:
Ok so pulled the fan brushes worn but fan works OK.
Bearings quite stiff so hit them with some lube, much better but this little fan sucks some amps !!!!
the front panel is the digital type and my meter indicates 13.9Volts initially when the fan is turned on and increases on up to 14.3 volts.
So Im moving to the MSI have I got that right ?
Click to expand...
I don't understand, did you get the fan running? You said "fan works OK"?
Where are you measuring the voltage? How did you test the fan motor? Did you apply external power to the fan motor and monitor the current?
If you are measuring voltage ("12V" in the loom connector) when the fan connector is disconnected from the fan but the fan wont run when you reconnect the loom to the fan, then the problem will be the speed controller.
Am I correct? When you pull the plug out of the fan motor you can read voltage (13.9-14.3V) in the loom connector but when you plug it back into the fan motor, the fan will not run?
 
I pulled the fan out and connected it directly to a 12 v battery and it worked, that's when I realised how much ampage it uses
The loom connector to the fan gave me n o volts with the fan switch off
And as I switched the fan switch on it gave me 13.9 and on to 14.3. But there was no variance as I selected the higher speeds.
From this my thinking is the problem is the front panel.
I'm thinking the stiffness in the fan bearings has required more amps to make it run intern placing stress on the front panel electronics.
 
Not sure what you mean by the front panel electronics but if you mean the dash controls it wont be that. There is a separate electronic fan controller module in the air distribution box. It is in turn controlled by the "front panel" electronics. But your theory is probably correct. The large currents drawn by the fan motor tend to burn stuff out.
I believe the fan speed controller is "leaking" voltage when switched on but the power is collapsing when you attach the fan.
These controller modules typically have one large Field Effect Transistor (FET) running the fan motor and the high current causes them to fail. There are a few repair videos on Youtube.
I think (but I'm not sure) the controller is up high on the air distribution housing on the passenger side. You might have to remove the glove box to get to it.
My son had a C4 VTS coupe with a similar problem a couple of years ago but that turned out to be the BSM.
There will be 4 large wires and a couple of smaller wires going into the controller. 2 large wires will go to the fan motor and 2 more large will go back to the engine bay. The two to the fan motor might be black and red, the two going to the engine bay might be white or gray and green (not sure but should be easy to figure out).
The two wires going back to the engine bay will have "12V" with the ignition on (or engine running) and no volts with the ignition off.
If you can hook up a load (like a 12v lamp) to the connector of the wires going back to the engine bay, that will test the BSM circuit.
Unfortunately a multi meter will read voltage but is not enough of a load to test the circuit's ability to carry current. Which is why you are reading volts with the fan motor out of circuit but the fan doesn't run when plugged in.
It's still possible it's a problem in the BSM but if you can get a lamp onto the wires going back to the engine bay that will tell you if it is.
An alternative would be, if you can get your multimeter probes into the back of the connector on the speed controller (and get a reliable connection). Plug everything in. With the fan set to run there should be 12V at the input to the speed controller (wires from the engine bay) with the ignition on or engine running.
 
C4 heater assembly
c4 heater.jpg
 
Don, 20 is the fan control module you are looking to test next as per my post above.

Cheers, Ken
 
Have bought new Fan controller resistor unit #20 and ordered another fan as there was a cracked blade on the existing unit.
Swapped the BMI over from the C4 Vtr to the troubled C4 vehicle. Definately a fault in the BMI as no blower in the donor car when swapped out.
 
We have a positive result. Replaced BMI resistor and fan motor. All working as they should.
many thanks to everyone that contributed to the fix with advice and wealth of knowledge.
 
2005 Citroen C4 2.0L Exclusive, dual climate control. This little car has me beat. Previous bridge fuse hasn't fixed it as fan would turn off; tried a different BSM -it destroyed that then 2 hour dangerous wait for tow on the Houghton Highway/Hornibrook bridge, so replaced the Fan (from a 2010) added a new controller, then that was faulty and had to send back (always ran on high with the ignition on or engine running a/c off) actually the old controller still worked, then the throttle body actuator failed - again towed. Replaced the the throttle body works again now car drives yet the fan doesn't. What else can be replaced?? the car is destroying everything within the electronics due to this fan issue. it is a friends car; my daughters same model has been a great car. Engine is fine, AL4 actually good, 152K. Old BSM is back in, need another that matches as it must be damaged yet something externally to this must be causing the issue. Why does the bridge fuse work? is it bypassing a relay? Wouldn't that mean it would always run?
 
If the Fan was running flat out with the switch off its the resistor unit just under the fan itself.
I replaced the Fan and the BMI and the resistor unit. The old fan cooked the new resistor unit so I replace the fan after the BMI and put the old resistor unit in and all good. Make sure aircon is all turned off before you start the car after replacement.
my main problem was fan motor wear that caused all the other problems. Have a read of the other posts above theyre invaluable.

Try using the BMI out of your faulty vehicle and test it in your daughters car, if eveything works then its all good. They are plug and play so no problems with the vehicle not being happy there. This is what I did as we have two C4s. Second hand BMI is about $120 to $150 and the fan motors are about the same, the resistor units are $40 on ebay made in China from local source.
 
Thanks so much Don. Actually a day later with the replacement Throttle body, replacement fan & original resister back in the faults have disappeared & the car & auto Ac is working again. Fingers crossed 🤞
 
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