pin 3 is the supply voltage to relays coils from 5A fuse (21) pin 4 not 100% sure but looks like it a sensor wire to ecu to let it know the fans on (wire to connector C C4 of ecu) 2 pin. pin 1 output to fan Pin 2 supply voltage to fan from 30A fuse (f1) not sure what the wire colours are as the diagram i got show numbers. Fuse box diagram Citroen C4 Picasso and relay with location and assignment. Full designation of fuses and relays Citroen C4 Grand Picasso (2006 - 2021 ) with diagrams and photographs of Glove box Front passenger airbag deactivation switch 14. Centre switch panel (lower and upper) 15. Side switch panel 1. External lighting/direction indicator controls 2. Wiper/screenwash/trip computer controls 3. Steering mounted gear control paddles (with automatic gearbox) 4. Speed limiter/cruise control controls 5. Audio system setting controls Fuse and relay location. Fuse box diagram. Cigarette lighter fuse. Assignment of the fuses and relay Citroen C3 Picasso 2008-2017 Got the same problem with my wife's 2008 2.0hdi Grand Picasso. All the fan controls work etc but won't blow. Rear seat fans work ok. No fuse for the front blower listed. I think the fan is under the dash above the pedals but will be having a look tomorrow to see if I can sort it. Therefore I had changed the wrong fuse from 10amp to 15amp. But in close inspection i found out that the layout of fuses in my car was different, it is the same as in your car. The fuse had gone and once I changed the fuse it is up and pumping, so once again, thank you Daza. By the way I own a Citroen C4 Grand Picasso 1,6L Diesel VTR+. Here you will find fuse box diagrams of Citroen C4 Picasso II 2013, 2014, 2015, 2016, 2017 and 2018, get information about the location of the fuse panels inside the car, and learn about the assignment of each fuse (fuse layout). Willem's Picasso is the earlier model, so not of much use to you. I have created a 'conversation' for you to ask frenchie about towbar fitting if you want. Otherwise, call around the wreckers and find a 2014-on B78 series Picasso towbar kit, noting that not every car will have had the wiring in addition to the towbar fitting. I have a 15plate grand c4 picasso and exactly same problem has occured. Exit and lock the car and the Heater fan is still running. After approx. 5 minutes it goes off. Unlock the car and it immediately starts up again. The heater / air con never really cooled the car down and suspected I would need to have it regassed or something. Then for next eight months it would blow a fuse once a month I took it back but nothing was found recently that has now increased to fornightly or weekly and in some cases daily. I've recently fitted an standard fuse box rather that keep buying Citoen fuses at over £1 a shot, these fuses cost me 25p. Fuse rating is still 30Amp. Other info. fu8zb.