Hello all, would really appreciate some advice.

On my 1997 S420, I've been dealing with a mystery water intrusion problem into the cabin air filter compartment. Every time I wash the car (admittedly at a touchless automatic car wash) the blower fan resistor gets wet and needs to be replaced. I understand that at automatic car washes the water pressure is high, but I've never had a problem like this in any other MB. I've narrowed it down to the water entering around/above the cabin air filter, because it also gets wet. I've triple checked that the whole cover assembly is tight and installed properly.

The only thing I can think of is that there is a small hole in the back of the assembly right around the cabin air filter. I have no idea what it's for, possibly a vent?

I'd appreciate any advice, and would be extremely appreciative if someone with an M119 car could take a quick look at the back of the cabin air filter cover and see if on your car that hole has something attached to it. Maybe there was a hose that dried out and disintegrated and fell off.

Thanks in advance!

OP is the drain plugged up in the cowl at the base of the windshield?

I will check!!! Could you easily explain exactly where it is? I googled around but it doesn't seem very clear.

I don't have all the drain locations but I also wanted to find all my drains on a W219. I took a couple glasses of water and poured it around the front areas to see where the water went. Whereever the water goes there should be drains, you can then check to see if they are clear. Don't forget to look under the hood around the firewall as some water can get there. Anywhere the water can get, check for the drain and make sure it's clear.

Outside corners of the cowl under hood. If you can see leaves ect... start there.