Instrument Condensation Cured

[virden]

Many thanks to the person whom a month or two ago recommended cutting a small slot in the rear of the tub containing the instrument gubbins,  I did this to my fuel guage and for the first time in ten years the internal glass face has remained dry in all conditions.

[Jonathan Kay]

Even with the decreased heat output of LEDs?

:-)

Jonathan

[SM25T]

Once the air inside the gauge is at the same temperature and humidity as the air outside it ... condensation won't form. So any aperture between the two will help. Just don't saw into the internals !!

[virden]

For some reason my fuel gauge always has suffered from condensation,and surprising quickly.  I am wondering if its position as first on the left side meant that it received a hot air stream from the extended footwell which is close to the  4:1 manifold. 

[Jonathan Kay]

Once the air inside the gauge is at the same temperature and humidity as the air outside it ... condensation won't form.

Imagine a cold car at the same temperature as the dry air outside and inside the gauge. The air is then replaced by warm wet air just warm enough to hold all of the water. With a big communicating slot that replacement is instantaneous inside the gauge when the air changes outside. But the new air cools on contact with the cold gauge below the point where it can hold all of the water. Water is then deposited on the surface. 

It's the thermal inertia of the gauge etc that's responsible, not only what's in the two air spaces.

Jonathan