I know - doesn’t make any sense to me either! There must be air getting in somewhere ‘cos it’s getting blown out of BOTH ends of the system! Yeah - good call!

Hi Flossie, Yeah - you can really feel it if you put your hand over the vent. It’s also definitely leaking round the join between the vent and the heater box (the one with the round foam seal). Got some copper pipe - going to take it all off at the weekend and strip it down.

Right - so didn’t have any time today other than I managed to confirm that the same thing happens when hot or cold is selected. So - job for next weekend is stripping the lot out and having a look. Thanks for replies - really helpful - will post what I find!

Hi Nobber. Pretty sure the flap opens and closes. I get decent air flow into the cab as well - just a lot escaping via the wing vent too. I’ll check again on cold tomorrow and also have a look with a torch. Need a new seal on the flap maybe?

No - it’s definitely blowing into the cab as well.

Hi all, when my heater fan is running (defender TD5) a LOT of air is being blown out of the wingtop vent. I presume this can’t be normal? I must be losing a lot of hot air out of the truck, and presumably letting cold air enter the system? The heater has never been brilliant - thought this...

Cheers both - will give that a go.

Hi all, Is this normal. When I rains in end up with a huge amount of water just sat on top of my roof (defender 90). Can't be normal?roof looks like it's sagged - anything I can do to support it from inside? Not sure you can see in the picture. Any advice appreciated!