On our car there were two issues relating to the heater/aircon box.
On the side of the box, under the bonnet, there is a drain spigot that comes out just above the footwell and near the ECU cover. Condense water from the aircon drains out there and used to run under the ECU cover and past the main cable grommet to drip into the footwell. In my case, LHD car, on the passenger's feet. To resolve this I added a silicon drain tube to the spigot and put a neoprene gasket under the flange on the ECU cover. To tell the truth we have started to get an occasional drip again so I must check both the drain tube and the gasket.
The other issue was water spraying out of the lower vents, from the lower airbox, again into the footwell. It turned out that the drain tube(s) (can't remember if there is one or two) are in a flexible, fairly soft, clear plastic and were bent or squashed flat. Some re-routing resolved the problem. I must also check this again to make sure it is still OK.

Both these issues related more to the aircon than rainwater so I suspect that in some way rainwater is draining out before getting in to the main chamber of the heater box.

Last edited by Gambalunga; 07/10/20 08:26 AM.
Peter

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