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Old 01-19-2010, 11:16 PM   #1
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weird defroster issue

We are heading to AZ and it is getting Biblical with rain and besides the wipers almost falling off (tightening them from inside the generator slideout is a job for a 30 lb monkey not a grownup) the defroster has decided to get weird.
When we are sitting still it works great, but when we are going down the road the volume of air drops by at least half - maybe more, I can't really tell - and the windshield really fogs up. Exciting; foggy windshield and detaching wipers make for an interesting trip in the rain.
The actuator and the switch seem ok and my guess is that airflow coming in at speed is opening/closing the defroster flap.
Anyone experienced and solved this?
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Old 01-20-2010, 01:43 AM   #2
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I would, when possible, look for a vaccum leak under the hood area. You should be able to find the reserve tank, usually a black round plastic tank with hoses connected. If you have good airflow while setting still, and loose that much airflow while driving , I suspect a bad connection or vacuum leak. The defroster does not use outside vented air, it is recirculated inside the coach area. For the time being if possible, use the dash a/c, which sometimes works better than the defroster, and momentarily switch it to defrost and if it starts to cloud up, switch back to a/c. I hope this works for you, it's worth a try. Good luck, travel safe, and Happy trais to you and yours.
David G.
USAF 1959-1963/ JFK Innaguration parade 1961,
1997 Fleetwood Southwind 37Y, 460 ENGINE on FORD chassis, Power Platform with Tag Axle.
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Old 01-20-2010, 12:20 PM   #3
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Thanks David....

I looked under the dash and in the generator compartment (it is a 2007 36' FDTS Alpine) and couldn't find an accumulator. I did find a number of vacuum or pressure controlled actuators - judging by the airlines running into them - but no accumulator.
Frankly, it looks a lot more complicated under there than I expected.
I did see exterior intakes for the a/c plenum but no intakes for the cabin.
So, the confusing, along with my anti-rain cussing grows.
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Old 01-20-2010, 02:05 PM   #4
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See link for a picture of the vacuum pump for my 2006 Alpine Coach Limited. It is located on the driver side, outside the firewall above the master brake cylinder.

Dale & Karin
2020 Winnebago ERA 70A
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Old 01-20-2010, 02:39 PM   #5
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I am not sure if this is what you are talking about or not, but will share with you my experience with the Alpine dash Heating and AC system. The air intake is behind the front cap and the air feeding to it, comes from under the coach. As the coach speed increases, there seems to be a slight vacuum created at the air intake. I have found that at speed I always have to turn the fan speed up to have the same air flow as at low coach speed. A head wind will also exacerbate this problem. This has been the same on my 2002 and this coach.
Dale Gerstel
Las Vegas, NV
Had: 2007 Limited SE 40fdts
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Old 01-20-2010, 04:44 PM   #6
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I have found the same thing as Dale. It depends on which way the wind is blowing. On vent I get little air flow unless I crank up the fan. I typically use the AC on recirculate to get consistent air flow.
Jim A
'04 Alpine Coach 36' MDDS
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Old 01-20-2010, 08:31 PM   #7
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Thanks Dale, Dale and Jim....

I found the vacuum pump right where you said it would be. I thought it was the motor for the wipers. I'll check for good connections, cracks, holes etc.
The air flow issue seems to be a design flaw that maybe some sort of shroud/deflector would cure. Maybe even boost the flow.
Has anyone given that a go?

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Old 01-21-2010, 11:05 AM   #8
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I hope that you aren't driving to "Q" today. Sit somewhere, today is not the day to be traveling in a high profile vehicle in the desert! It isn't raining cats and dogs anymore, we're way, way past that.

Barbara & David O'Keeffe
Figment II (Alpine 2002 36 MDDS)
On The Road since 2006
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Old 01-21-2010, 11:09 PM   #9
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No, we aren't headed to Q, but we did decide to stay in Needles today and it rained as hard as I've ever experienced in the Northwest.
Bullhead City (my juvenile, evil twin wants to sneak up to the city's entrance sign and cross the two "L"s) had about as much water in the streets as I saw in the Colorado River today.
Time for SUN.
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Old 01-22-2010, 10:50 AM   #10
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I have never had that problem with the Defroster (Read on) but have with my AC.. When accellerating the A/C basically cut off, or so it seemed. I thought it might be the ECC doing so to amp up the power to the wheels but turns out it was not.

I had a vaccum leak, and when I hit the gas the vacuum went to zero, so the HEVAC system went to it's DEFAULT setting which on GM designed systems is DEFROSTER (Which is why I've never had that problem)

Other makers may default to "FLOOR" or "VENT" I don't know.

But the symptom sure sounds like a different version of the exact same problem I had.. The leak, in my case, was internal to the cruise control.
Home is where I park it!
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