Condensation in cab

[71 C20 CS]

My cab is getting really wet inside on the roof and windshield. The door seals are new and I checked they’re sealing properly and there’s no leaks, carpet is dry everywhere, but somehow moisture is getting in, there is so much condensation on the roof, it gets really wet, I have to towel it off.

Anyone have any experience with this? I was told by a mechanic to put dynamat on the roof and it will stop, but that sounds odd to me.

[GASoline71]

I'm assuming by your handle that you have a '71 C20. How is the driprail seal? Is it all chipped out and rusted?

I live in western WA and know how wet it can be, and we've had a LOT of rain lately.

Gary

[71 C20 CS]

Originally Posted by GASoline71

I'm assuming by your handle that you have a '71 C20. How is the driprail seal? Is it all chipped out and rusted?

I live in western WA and know how wet it can be, and we've had a LOT of rain lately.

Gary

The drip rail is in good shape, no rust on the roof.

[truckster]

Do you have leaves blocking the cowl drain holes under the vents?

Also check the bottom of the windshield, the cowl area, and the firewall for rust.

[dagnabbitt]

Generally speaking indicates a heater core issue, even in modern vehicles.

[68 C10 Driver]

Originally Posted by dagnabbitt

Generally speaking indicates a heater core issue, even in modern vehicles.

Good starting point...71 C20 CS, does it smell or even give you that "taste" of anti-freeze when you drive it?

[71 C20 CS]

Originally Posted by 68 C10 Driver

Good starting point...71 C20 CS, does it smell or even give you that "taste" of anti-freeze when you drive it?

I don’t think it’s the heater core, no coolant smell or leaks, the cab seems tight I don’t understand where it comes from. Even with a waterproof cover and tarp over it condensation still builds up.

[71 C20 CS]

Originally Posted by truckster

Do you have leaves blocking the cowl drain holes under the vents?

Also check the bottom of the windshield, the cowl area, and the firewall for rust.

Cowl is free of debris.

[Getter-Done]

Are the Fresh air vents opened or closed?

Do they have debris or leaves in them?

[GASoline71]

Oh, and do you have clearance lights on the roof?

Gary