Constant blower fan at full speed - Citroen C4 Picasso

[8v_chris]

Hi all, my brother picked up a 2008 C4 Picasso which he loves but it has the blower fan for the heating going full chat all the time. I’ve been fiddling with it to try and sort it but so far we’ve tried the following with no change;

- changed the resistor that sits into the bottom of the fan itself and also checked voltage. 13ish volts down the live feed which is then passed through the resistor and out the other side to the fan itself with no voltage drop. Smaller black square plug has no voltage at all under any circumstances. The resistor isn’t a cheap Chinese one, I deliberately looked for a decent one which ended up coming from AUTODOC.
- reset the BSI but no change either
- pulled the relay from in the front of the fuse box in the engine bay and cleaned contacts with no change. Also swapped the relay out for a known good one but no change there either, pulling the relay out stops the fan altogether.

I’ve been in under the dash and can’t see a master relay or anything else that might control the fan. The loom from the big resistor seems in good order when the tape was peeled back and when tracked back into the car it disappears up behind the dash.

His vin number is VF7**************[VIN obfuscated, can be read by forum staff].

Is the something I’m missing or should be checking? Thank you

[GiveMeABreak]

So just to confirm this is what you've replaced?

[8v_chris]

Yes although his was a different shape, it’s the squarer type with him not having automatic air con. He doesn’t have the digital screens controlling temp either side, just the twist dial

His was this shape -

[GiveMeABreak]

Yes, that's the one. Just wanted to make sure - I used a poor picture previously.

So if this has been replaced with a decent branded replacement, I would be looking to the actual control unit on the Driver's side. These are still electronically controlled, but are no longer available new from Citroen.

[8v_chris]

The actual twist dial? I’ve seen some on eBay for about £20 so at least there’s second hand ones available. Are they prone to failing?

[GiveMeABreak]

Like all electronic components, with buttons and dials, they will wear out the tracks or the contacts, so it's likely something like this may have happened.

There are multiple versions of these depending on model and options, so make sure you get the correct one.

Like this....

https://www.ebay.co.uk/itm/276489543980 ... BM0oPyubRk

Or this one in better nick, you can just remove the vent from the control.

https://www.ebay.co.uk/itm/296644684387 ... BM0oPyubRk

In either case has to be worth a punt for the money.

[8v_chris]

Thanks for your help, I said to him and ones in the post. I’ll report back how it goes!

[8v_chris]

Like all electronic components, with buttons and dials, they will wear out the tracks or the contacts, so it's likely something like this may have happened.

There are multiple versions of these depending on model and options, so make sure you get the correct one.

Like this....

https://www.ebay.co.uk/itm/276489543980 ... BM0oPyubRk

Or this one in better nick, you can just remove the vent from the control.

https://www.ebay.co.uk/itm/296644684387 ... BM0oPyubRk

In either case has to be worth a punt for the money.

So he got a new (to him) unit but it made no difference, still at full chat. Now I’m really lost as to where we go next

[GiveMeABreak]

So what brand was the heater blower control module he purchased - and where did he get it from?

[8v_chris]

Exactly this, same brand, but was bought via autodoc.

https://www.ebay.co.uk/itm/23562208056 ... SwC7tmeQwm

[8v_chris]

Bump - does anyone have any other suggestions before I swap out another resistor to see if I’ve a bad one out of the box. Or is there another resistor somewhere else behind the dash? I see some have rear resistors too, can anyone verify if this is the case with what I’m looking at using the vin in the first post? Thank you!

[8v_chris]

SOLVED!! So it turns out the it had the wrong blower motor fitted and therefore the wrong resistor pack in the bottom. I swapped it out for the other type of resistor and blower motor and it’s back to normal so I guess that was the issue from the beginning and it also explains the reason the the plug on the loom for the motor appeared to be the wrong one.