Slight fog in left, combined instrument

[pmansson]

This is not a new subject, but today I took out the red one from a 13 degree garage, and drove it in 7 degree outside temp (Celcius). After a short while the bottom part of the instrument glass had mist/condensation on the inside. After a while the heat of the lamps (it was dark outside) cleared the fog.

On another occasion, another E9 had been parked outside over the night with similar outside temperature. Half the glass had condensation from the start.

It doesn´t happen on all such occasions.

Why does it only happen to the combined instrument on the left?
Can it be caused by vent flaps being open on the heater box?

Very strange....???

 

[Honolulu]

it's just condensation

Condensation of no particular source. It requires moisture and appropriate temperature to make airborne gaseous water condense.

It's possible you have a hidden windshield leak around there.

I've read elsewhere that some Downy or other clothes washer anti-static stuff, rubbed on the interior of the instrument glass, will prevent condensation, and deter bits of dust from sticking to the glass. But you'd have to remove the instrument and cover glass to apply.

 

[pmansson]

No leaks from anywhere around instruments. New windows and seals on all cars. The amount of fog/condensation is minmal but quite visible.
Doesn´t leave stains on inside of glass when dried up by instr. lighting.
Weird....

 

[tochi]

Fogging

I can think of several moisture sources.:cry:

The most obvious may be the windshield/gasket, but anywhere near the firewall where the heater and wiper assembly reside becomes a likely place for moisture to pool. Albeit unlikely, it is not impossible for moisture to be sourced to a coolant/heater leak, air conditioning condensation or even some aberrant windshield washer fluid. There is also a possibility that moisture can follow the lead attached to a radio antenna - under the dash. I discovered this happening in another car when trying to track down mold in a glove compartment. This, presupposes you have a car that might be washed or exposed to rain or even a humid climate. Although I do not expect this to be the case in E9's and especially in the underdash area, sunroof gaskets and drains are also notorious moisture concerns.

Just like oil leaks, gravity, coupled with wind can direct fluids/gases in the unlikeliest of places. :wink:

 

[Arde]

I have exactly the same symptom. The car is garaged, no driving in the rain, not much rain here anyways, and the condensation only occurs while driving in cool nights. I took out the instrument once and left it under the sun with
the lamp openings up to try and evaporate any internal humidity. Humidity came back.

I have a spare instrument, so next step is to try that one. I suspect that
sealing the instrument is more important in the back where the cables get in. We'll see.

 

[pmansson]

Exactly !!
talking about leaving the instrument in the sun... I have had Euro lamps (not sealed beam à la US) get foggy inside. I took them out and put them in the oven at atout 60 degrees C for a few hours, and it all dries up.
The cover cup is not tight enouh !!

Reg Tochi: this car has no sunroof or antenna in the front left fender.
One of the two has A/C but this system was checked last year.
Heating unit: perhaps, but why condensation on ONLY the combined instrument ???

As the condensation happens only once in a while, and only covers a quarter, at most, of the glass, it is not too much to worry about.

Still a mystery.....

 

[Honolulu]

condensation

The physical facts of condensation is that it happens when the air temperature drops to or below the dew point. In plain english, when the air in there gets cold (enough), water vapor will condense.

Ergo, keep the air in the pod warmer, or drier, or treat the surface with a material that lowers the surface tension of the condensation so it spreads rather than forming as little beads of moisture.

I doubt that removing and warming/drying the instrument will be effective for any length of time, but I could be wrong. That's certainly happened before.

Can you keep the instrument just a little warmer? That could work. Maybe one of the backlight bulbs on when the key is on? Higher wattage bulbs in there?

Another approach ... maybe MORE ventilation to that pod is what you need, so that the humidity isn't trapped in there and it can remain at or closer to ambient, which as you noted isn't causing problems with the other pod units.

 

['69 2800cs]

This is something the air cooled 911 guys have to live with as well. Those gauges are similar to the E9.

The suggested culprits are the same-leaky gaskets, water infiltration. However, my 911 hasn't been driven in the rain in years, yet the right combo of temperature and moisture outside and bingo! Fogged gauges.

It wasn't long after the E9 that most cars went to gauge "pods" with plastic lenses, as opposed to individual metal gauges with glass lenses.

I bet the change to plastic is one of the reasons we see this more in the older cars.

 

[bill]

foggy glass

I have always had fog on the temp gauge. My 74 is always garaged and never driven in any kind of airborne water. Must have something to do with moisture in the air and heat from the gauge? Just one of those things one must put up with to have one of the most beautiful cars ever made....

Bill