Fogged-up gauges

[gouldsborough7]

With the cold weather, I expect a lot of us are experiencing problems with trying to read dashboard gauges through a fog.

Mine are Smiths, and the worst offender is the rev counter. Combined with poor electical lighting, this gauge is useless at this time of year. Strangely, the smaller gauges: petrol, volts and temperature are all OK. Same duff lighting, but otherwise no problem.

My Japanese wagon never has such problems, so what's the differnce? I guess the glass seal is poor, and irregular short journeys doesn't help.

Anyone got ideas on how to cure this? Take the guage indoors for a few days to dry out, and apply liberal sealant?

Cheers
Mike

[Dane_Rescueman]

Re: Fogged-up gauges

Mike I had the same problems with my VDO gauges. the problem was only with the 50mm ones for Oil, Temp, Fuel and volts. The clock,tacho and speedo did not have the problem. I removed several layers of skin upon removing all the gauges. The bulb holder is only a push fit in these and I guess that over the years damp air had entered the casing. When driving with the hood down, the glass cools and the humidity condenses on the rear.

I put them all face down on our mantlepiece above a powerful stove for a week. They looked dry enough so I refitted them leaving my remaining epidermis spread liberally on the various projections on the rear of my dash.

I tried to seal the bulb holders with suitable heat shrink tubing.

I took her out today (-2°C). Guess what? fogged gauges...Sigh!

[gouldsborough7]

Re: Fogged-up gauges

Dane
Yes, I know the feeling. Spend time and get bashed knuckles only to resolve nothing sometimes! One of the joys of kit-cars is to sometimes sort out a real puzzle at no expense.

On a nothing ventured basis, I'll probably yank out my rev counter this weekend, stick it near some heat for a day, seal every possibly orifice with sealant, and will have a 50% chance of success.

Even though my Berli is stored in a garage, with the current weather, the gauges experience different climate conditions either side of the glass. They need to be double-glazed! My Nissan spends 365 days a year outside, and never a hint of problem.

Cheers
Mike

[macdonald.dm]

Re: Fogged-up gauges

Hi Mike.

I wonder if the main difference between the Nissan's modern gauges and yours is that the former are made from plastic which is a much better thermal insulator than metal, so the surfaces will 'feel' warmer and will be one of the last surfaces inside the car to have condensation form on them? (I bet, tho', that the inside of the windscreen in your Nissan is pretty misty?)

In theory, if you could fully dry out your gauges and then make them 100% air-tight, then condensation shouldn't reoccur. In practice, however, you are unlikely to manage 100% sealing and - even worse - any condensation that subsequently does get in then not going to shift very easily...

Two things contribute to condensation forming - one is low temp surface (oooh...), and the other is lack of ventilation. Once the moisture-laden air gets inside your clocks and condenses on the cold surfaces inside (glass and metal), there is virtually no air flow in there to clear it up again.

I'd have thought, tho', that the illumination bulbs would warm them up enough to clear them? Is it worth driving with your side lights on even during the day?

[h_m_cumming]

Re: Fogged-up gauges

Mine only mist up when the panel lights are on. If you think about it , as the bulb warms up the air in the gauge it absorbs any moisture around and when it hits the cold surface of the glass condenses out onto the glass. Modern cars tend to have their gauges behind a plastic panel and often with LED lighting thus generating hardly any heat.
I get over it by driving around in the dark. No change there then!!!

[macdonald.dm]

Re: Fogged-up gauges

That's an interesting take, Hugh.

My understanding is that warm air can hold more moisture in it. Which is why, for example, it's when you turn off your central heating at night that condensation forms on the insides of your windows - the air cools and cannot hold the excess moisture any more. So, this then condenses out on the coldest surfaces it can find - your windows.

What might be happening inside your clocks is: the inside of the metal case and the bulb holder, workings etc all have condensation on them. When the bulb is lit, this warms these areas and the condensation evaporates into the air inside the clock making it pretty well saturated. The moisture in this air then condenses on the next coldest surface it can find - the clock glass.

Since the clock case is pretty well sealed, it isn't easy for this moisture to escape.


Ok, someone would need to be willing to try this, but I suspect very strongly that if you drilled a few little holes in the top and bottoms of a problematic instrument case to allow gentle air circulation, I bet your condensation problems would soon be over.*

Anyone here have safety goggles? The ones that seal against the face? See all the vent holes which helps prevent the 'glass' from misting up on the inside?

(*But don;t come crying to me if... )

[b_caswell]

Re: Fogged-up gauges

If your keeping the car in the same garage as the butane heater then the air will be moist as the heater produces water when it burns the butane. Then as everyone else has said the inside of the gauge gets warm and the clock face is colder than the moist air. If you can take the glass off you could try using an anti fog agent on the back of the glass.

[milliemarlin]

Re: Fogged-up gauges

Millie suffers from foggy gauges. I have driven out of the garage with clear gauges, have them fog up after about 20 minutes driving, then clear again. This was all during the morning with no lights on.

The speedo and tacho are the worst by far. I think that the bulbs do contribute to the problem but in Millie’s case the windscreen demister pipe is close to the rear of the gauges. The gauge housings are metal and will conduct the heat into the interior of the gauge well. Certainly the draught free area under the dash is much warmer than the air on the front face of the dash. The fairly saturated moist air inside the gauge condensates out onto the cold glass. I suspect it is the warm air cold glass combination that causes the problem. I think the smaller gauges are less susceptible because they do not extend back towards the demister pipe and the plastic housing is better insulator. The modern gauges are a think plastic and will not be as cool as the glass ones.

I have not found a good solution to this. I have contemplated two ways. The first is to increase the flow of cold air around the inside of the dash and gauges, as suggested above. The second is to increase the flow of warm air to heat the glass. The second method is the one that stops the windscreen misting up. I don’t think you will easily seal these gauges. Even if you did I think you will need to “dehumidify” the contained air or gas some way.

These gauges are not cheap and I have been disappointed that this has not been solved by the manufacturer.

Paul

[gouldsborough7]

Re: Fogged-up gauges

I wondered what happened with gauges in genuine open-top classic cars, especially the pre-war Jags, Lagondas, Bentleys or whatever? The owners would not have accepted these problems.

You will see some of these in Agatha Christie dramas, where they did't even have a hood over the Chauffeur! The gentry sat in comparitive comfort in the covered-in back-seat area, while the driver was dressed in waterproof clothing, and suffering whatever the sky threw at him!

Mike

[Dane_Rescueman]

Re: Fogged-up gauges

My '58 frogeye and '52 TR2 didn't fog up - they were old Smiths or Jaeger instrument types. They were all mechanical including the tacho and had lost a lot of accuracy in their time. During this time I owned no hood for either car. I no longer own the cars.
I had a Rover SD1 in which everything fogged up regularly but these great cars had ropey seals on the bulkhead heater hoses which caused a lot of hot moist air (steam!)to circulate around the rear of the dash.
My ancient Ferguson tractor fogs it's gauges all the time in most weathers. This has no heater so I guess moist air gets past the seals and condenses on the glass.
Miss Marples would quickly work out the causes I expect!!

[macdonald.dm]

Re: Fogged-up gauges

I suspect it's down to the combination of heat and cold in our 'modern' marlins...

Warm air holds more moisture. Get in to your cosy Marlin and the air inside begins to fill with moisture. When it cools, the excess moisture it can no longer hold condenses out on the coldest surfaces first.

Hoodless pre-war cars were pretty much the same temperature throughout!

As pointed out in the posts above, there are other factors too - where the car is stored, whether it's shut or open (or hood on or off*), proximity to heater pipes, cold draughts... etc.

I still reckon the single best solution to this problem are a series of tiny (eg: 2mm dia) vent holes top and bottom of each clock case.

Attempting the opposite solution - making the clocks airtight - will almost certainly lead to problems; remember when your 'waterproof' watch finally became misted up inside - and no amount of heating dried it out completely?!


(*When I park my Berli in the garage with the hardtop fitted, I always leave the car doors open especially if it's wet from rain. The inside is always remains bone dry due to air circulation - I'm pretty sure it would be misted up if I kept them shut.)

[dogoncrazy]

Re: Fogged-up gauges

On a slightly different note my 'Omega' wristwatch fogged up in the heat of Death valley U.S.A .Completely sealed waterproof unit, anyone explain that?

[Dane_Rescueman]

Re: Fogged-up gauges

I find that with my Omega the screw down winder sometimes undoes itself. I found this once after diving. Drat! I sent it off to be cleaned out and serviced. Ker-ching! I often check that the winder is screwed fully in now!

[h_m_cumming]

Re: Fogged-up gauges

Get a Seiko

[b_caswell]

Re: Fogged-up gauges

My Casio would fog up after being in a burning building at 800c at ceiling level then being soaked with cold water at 100psi. It was water proof to 100metres and Casio couldnt work out how it kept leaking!