Hello all, Ducato 35 maxi160 m-j xlwb 2011 I have a rear heater,did anybody ever find out exactly where the solenoid to allow the water through is.I asked the same question some years ago & never got an answer.
Also has anybody fitted a passenger air bag aftermarket & how much.
Thanks Rieaa.

Replying to this myself,checked the door pillar fuses/relays all ok traced piping back to main heater radiator & after lifting battery cover & trim with mirror & torch found solenoid on r/h side,there it was the solenoid activating wire was too short & had never been connected so released socket from it's fixing joined the two & it all worked fine. Thanks Fiat for six years rear heat not working !
RIEAA

Thank you for update , informative and will no doubt help others .