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ross kowalski
Grand Master
Username: cdfpw

Post Number: 337
Registered: 11-2015
Posted on Friday, 31 March, 2017 - 08:35 pm:   Edit PostDelete PostView Post/Check IP

Patrick,

Great, photos thanks for posting.

The fog in the gauges is your car reminding you to run it more often. I just started my car for the season and while it fired right up, the gauges all had that fog until I ran it for a couple days.

The heat of the gauge electronics eventually causes the fog to evaporate.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1367
Registered: 9-2004
Posted on Sunday, 28 May, 2017 - 02:38 pm:   Edit PostDelete PostView Post/Check IP

"but what causes the fog in the first place?"


The fogging up on my cars amp meter was caused by heat built up on the connections, the cause, a high resistance on the connections.
When I first use the car when the charging is shown 50amps and decreasing the problem then shows itself.
The air con helped take the moisture away!
Undo the connections and clean after dash removal.
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Christian S. Hansen
Grand Master
Username: enquiring_mind

Post Number: 603
Registered: 4-2015
Posted on Sunday, 28 May, 2017 - 08:28 am:   Edit PostDelete PostView Post/Check IP

Ross...

...but what causes the fog in the first place? More specifically...why might some gauges get the fog while others do not? I have just that circumstance with an EPW Silver Dawn. One set of cluster gauges gets fog. The other does not. Since the moisture in the atmosphere (humidity) is theoretically the same, I have assumed that the moisture must be coming from some other source. While I have casually (and worriedly) observed the phenomenon, I have found no correlation as to when it happens, day vs night, hot weather vs cold, dry weather vs rainy, et cetera, other than when first using the car, and noticing that after 30 minutes or so, it dissipates (evaporates?).

.
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John Beech
Grand Master
Username: jbeech

Post Number: 402
Registered: 10-2016
Posted on Monday, 29 May, 2017 - 03:43 am:   Edit PostDelete PostView Post/Check IP

OK, I see we've hijacked the thread about ethanol so I will start a new one, instead of continuing. Else nobody will ever be able to find the conversation and gain anything useful.
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Jeff Cheng
Frequent User
Username: makeshift

Post Number: 94
Registered: 2-2016
Posted on Monday, 29 May, 2017 - 10:54 pm:   Edit PostDelete PostView Post/Check IP

Going by experience from window glass, the cleanliness of the glass can determine how quickly it will fog up.

A dirty windscreen will fog up more easily than a perfectly clean one. Similar to clouds, the water droplets form easier when there is a particle to start on (grime).
Ever fog up the bathroom mirror and wipe it down, then the next time, it first starts to fog on the old water marks where it was wiped? Those watermarks is the 'grime' for the fog to start.

The story with clouds goes something like the air above Antarctica was once so pure that clouds never used to form, as there was no dirt particles to act as a nucleation point for the water particles.

But I digress...

Applying a surfectant such as Rainex, dish soap or even a potato (on spectacles) will delay the formation of water droplets, as the surfectant reduces water surface tension, so the water moisture doesn't form 'drops' as easily. Next time AFTER you clean your windscreen, put a few small drops of dishwashing detergent onto a paper towel and really wipe down the inside of the glass with it. Then buff the glass with a clean cloth until clear. Try breathing onto the glass and you'll see that it will barely fog from your breath.
Try it on any glass (glasses, picture frame) if you are sceptical.

Same theory goes for instrument glass. As the instruments heat and cool, the air expands and contracts, often sucking in airborne dirt. Now think of the last time the inside of that gauge was cleaned, and imagine not cleaning your windscreen for the same period and you can understand the 'dirt' inside those instruments.
Pull the glass, polish the backside with some dish soap and you'll never have fogging issues again.



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ross kowalski
Grand Master
Username: cdfpw

Post Number: 435
Registered: 11-2015
Posted on Tuesday, 30 May, 2017 - 01:39 am:   Edit PostDelete PostView Post/Check IP

Christian,

The mechanism by which the lens of a gauge fogs on the inside is pretty much like this. If you wear glasses you know it quite well. Work outside for a while on a cold day and then come inside. The warm humid are condenses on your glasses and there you go fog.

Because the gauges are fogging from the inside the air inside must be humid, and warmer than the lens.

As to how the humid air gets in there, well I suspect it's something like the heating coil on the bimetallic spring (and bulb if at night) heats the air in the fuel gauge, after the car shuts down the air in the car cools first then the contracting / cooling air inside the gauge pulls in outside air.

I think modern gauges with plastic lenses have a coating that prevents fogging so it might be possible to order a relacement gauge lens from VDO or Autometer and fit it. Also, if a cheap gauge from ebay had the treated lens, you could order it and strip the lens out if it was cheap enough.

Good Luck.
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Christian S. Hansen
Grand Master
Username: enquiring_mind

Post Number: 604
Registered: 4-2015
Posted on Tuesday, 30 May, 2017 - 05:40 am:   Edit PostDelete PostView Post/Check IP

Ross...Yes, condensation as the fogging was a given and understood. My inference was as to the likely source of the humidity contributing to the condensation and why it sould be any different in one gauge than another gauge inches away. I had thought that perhaps there was a leak in the windscreen allowing moisture to penetrate behind the dash, but eliminated that as a humidity source as the fogging occured whether or not there had been any rainy weather (increasing the abmient atmospheric humidity) and irrespective of whether the car had actually even been out of the garage and into the rain.

I suppose that this will simply be another of those "you will never know" situations, but next time I am driving the subject vehicle I will pay more attention to which cluster gauge has the condensation and which of the gauges within that cluster seem to have it more than others in order to visualize the nature of that gauge in terms of the generation of heat that you referenced. Both cluster gauges have the same lighting so perhaps that can be eliminated as having an effect. I will also observe whether the fogging is there immediately, or develops after the engine is started and then dissipates after a time interval and as everything eventually warms up. My only recollection is that there was fogging and that it eventually dissipated

.
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Patrick Ryan
Grand Master
Username: patrick_r

Post Number: 1564
Registered: 4-2016
Posted on Tuesday, 30 May, 2017 - 07:31 am:   Edit PostDelete PostView Post/Check IP

I had fogging on my fuel gauge last weekend, when the car spent 2 days in the rain the weekend before.
Never had it before this though.
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ross kowalski
Grand Master
Username: cdfpw

Post Number: 436
Registered: 11-2015
Posted on Tuesday, 30 May, 2017 - 07:40 am:   Edit PostDelete PostView Post/Check IP

Christian,

When I get fogging it is usually the fuel and sometimes the coolant temp gauge. Never the speedo or the clock.
Both the speedo and the clock have more space inside, so maybe there is something to case size?

I ordered some anti-fog acrylic and will laser cut a lens from it for fitting in my cars fuel gauge.
I ordered .080 which has to be close to the OEM thickness.

I have been quite busy lately and have several RR projects that I have to get done so it might be a while, but if it works out, I will post a how to on the whole install.
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John Kilkenny
Prolific User
Username: john_kilkenny

Post Number: 264
Registered: 6-2005
Posted on Tuesday, 30 May, 2017 - 12:03 pm:   Edit PostDelete PostView Post/Check IP

Here's my theory about fogging.
During the colder months my car has always exhibited some fogging of the drivers side gauges (including speedometer) if it has not been driven for a few days.
The fogging does not appear until a short time after starting and remains until the engine warms.
We know that as air becomes warmer it will absorb more water so while the engine is running the under-bonnet hot air will also be contained within the gauges.
When the engine is switched off the gauges will cool to the ambient temperature.
Because water precipitation (dew) requires a temperature difference between the glass and the air within the gauge dew will not form at this time.
However when the engine is started again the back of the gauge and the contained air will warm quicker than the glass face and this will cause precipitation on the glass. This will disappear as the temperature equalises.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 73
Registered: 5-2016
Posted on Wednesday, 31 May, 2017 - 07:57 am:   Edit PostDelete PostView Post/Check IP

I've read in another forum that an owner came to the conclusion via trial and error that the gauge fogging occurs when the rubber glass seal gets brittle and allows a certain amount of air in. His cure was to either replace the rubber seal with a new one or remove the seal altogether and allow the air to circulate creating a vent for the moisture. I haven't tried either of these solutions myself.
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Patrick Francis
Prolific User
Username: jackpot

Post Number: 142
Registered: 11-2016
Posted on Wednesday, 31 May, 2017 - 04:53 pm:   Edit PostDelete PostView Post/Check IP

There are two little cork stoppers on the back of some igauges that block off the adjustment screws that sometimmes dry up and fall out - this may contribute.....
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Jeff Cheng
Frequent User
Username: makeshift

Post Number: 95
Registered: 2-2016
Posted on Wednesday, 31 May, 2017 - 06:05 pm:   Edit PostDelete PostView Post/Check IP

Ignoring temperature differentials; a 'dirtier' (old) gauge will fog up more easily than a clean (newer) gauge. And once it's fogged up the first time, it will fog up easier the next time.
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Patrick Francis
Prolific User
Username: jackpot

Post Number: 143
Registered: 11-2016
Posted on Thursday, 01 June, 2017 - 12:33 am:   Edit PostDelete PostView Post/Check IP

Maybe some "Mr. Sheen" on the inside and outside of the glass?

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