# Hymer S700 screen demist problems.



## jasp (May 26, 2005)

Anybody else have problems with the windscreen demisting on their hymer S700. 
It's a 1999 model on the merc chassis and coming back from the lakes today, the front screen took forever to demist. Even on full fan speed with the aircon on.

Any solutions?


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## Drew (May 30, 2005)

Hi Jasp,

When I had a similar problem with my Hymer, I removed the carpet and board between the dash and window and found that the hose supplying the blown air to the ducting had become disengaged. Not a difficult job to do but unfortunately I also found that the edge of the board had rotted due to condensation from the windscreen.

I hope this helps.

Drew


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## BillCreer (Jan 23, 2010)

The only time this happens in my van is when someone, without telling me, decides to put the heater on "cabin recirculation" rather than "external feed".
They do it in my car too!


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## flyingscotsman (Jun 23, 2007)

Hi Jasp,
I have the same Hymer year and model and had the same problem! 
When I opened the bonnet and felt the ducting that runs under the windscreen, easily spotted where connection had parted. Some large cable ties pulled it back into position, job done. Hope yours is as simple to fix.
Aye the flying scotsman


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## jasp (May 26, 2005)

Had a look under the bonnet and both the inlet and outlet ducting are connected to the heater/fan housing. 

I cannot see where the oulet ducting from the fan goes as it disappears into the bulkhead somewhere.

The fan does blow, but even on 4 speed is not very powerfull!


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## Bethune (Apr 21, 2008)

Not that it is much help to you but our 2008 S800 also has similar de-misting problems. I have not found the right combination of controls (recirculation, temperature etc) to get a speedy de-mist. This problem may be genetic !!
Philip


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## teemyob (Nov 22, 2005)

*Mist*

Our Frankia starts to mist up when we stop at lights or in traffic.

It is a crap system.

There is a switch over the hab door, a 2 speed fan switch. It is supposed to stop the screen from misting up when you are parked up. that does not work either.

TM


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## aultymer (Jun 20, 2006)

> I have not found the right combination of controls (recirculation, temperature etc) to get a speedy de-mist.


I would advise NO recirculation, maximum air flow and the engine will be cold anyway so temp setting will make no difference.
If the air flow from the heater/demister is lower than expected then try removing the pollen filter (if fitted) since it will do no good until spring and only restricts air movement.
With the controls set to 'demist' you should get the same volume of air through as you get from the heater - if not, go looking for kinks in big plastic ducts - some converters are none to careful in preserving original equipment runs.


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## kandsservices (Sep 5, 2010)

Does your cab aircon work correctly if so try using it with your blower on normally works as it takes the moisture out of the air.


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## mickyt (Mar 24, 2008)

*Demister*

I have a1998 A class, Te demisting isn`t great , but noticed I get better blowing wwhen turning . on investigation , I went underneath . There are two air pipes near the front bumper rhs . They are just hanging near the vent slits in the bumper . I presume one is feeding the fuel system and the other connected to the interior air sytem .
I am trying to make a proper ducting from the bumper vent to the pipework to see if that gets a better ram air effect into the vehicle .


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## jasp (May 26, 2005)

The aircon works fine, just does not seem to be enough force coming out of the ducts to the windscreen.


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## teemyob (Nov 22, 2005)

*fan*

I have a similar topic running for the same problems.

I have already found that in one of the lockers, the ducting had come adrift. However, even after re-connecting, the airflow is barely a breath.

I am going to fit an in-line fan. 12v that can be run with or without the engine running and that is connected to the Cab heater matrix and the Alde habitation heating.

The design of this frankia is great, pity some of it's function, fit and finish are not up-to scratch.

TM


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## vicdicdoc (May 14, 2005)

I have the same problem [on my Fiat based Hymer E-510] . . . the fan works ok for dashboard vents but is non existent for feet vents & very feeble for the windscreen demisting too . . I also am trying to figure out a system using a small 12v computer fan to direct warm air to the screen. 
Apart from dismantling the dashboard [which I'm not even going to attempt] - I can't figure out how to get to the 'heater control' mechanism which is obliously the culprit


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## dikyenfo (Feb 16, 2008)

Surelt the easiest way is to fix a normal 12V fan on the broad dash and that works well in all cases I use mine.


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## jasp (May 26, 2005)

Anybody use one of these, although it does look a bit small

http://cgi.ebay.co.uk/ADVANCED-CERA...arts_Vehicles_CarParts_SM&hash=item334a4424d2


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## teemyob (Nov 22, 2005)

*ebay*



jasp said:


> Anybody use one of these, although it does look a bit small
> 
> http://cgi.ebay.co.uk/ADVANCED-CERA...arts_Vehicles_CarParts_SM&hash=item334a4424d2


Should not have too when you consider someone paid £125,000.00 for the motorhome when new!

Here is a new example with less spec.

2009/2010 model


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## teemyob (Nov 22, 2005)

*Frankia Problem*

Having taken apart the dash, I found where part of the problem is. The end of the ducting has been bodged by Frankia during production.

Rather than cap the end, it has been foamed. But not foamed enough to seal to cap it, leading to loss of airflow.

I have now sealed it and will fit an additional 12v fan to increase the airflow.

I have also removed the useless air vents from under the seats. This has increased the airflow to the shower. Warmth and flow of air is now more like that of a tumble dryer, so should make a better drying area for the ski gear/washing.

TM


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## teemyob (Nov 22, 2005)

*This is what they should have used*

This is what is supposed to be in-place.

And I will fit this fan.


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