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[SOLVED] Cold air switches from face to demister under load 

 

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 Post subject: [SOLVED] Cold air switches from face to demister under load
Posted: Thu Jan 16, 2014 4:26 pm 
Getting Side Ways
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Hi guys,

I'm loosing my mind here, and really need some help :(
EB Fairmont - on LPG & Petrol (Petrol runs shocking, Ive replaced all components)

When my car has cold air on blowing through the face vents, under acceleration / load it switches to demist.
However when its on heat - 25degrees or more, this doesn't happen?


When I accelerate underload, I can hear the duct in the dash clunk to the demister.

*I've noticed the arm that pulls the duct open and closed next to the ECU on the passenger side is broken (however I don't think this would cause any issue?)


I've checked EVERY line and can't see a popped hose or hear any leaks, also went to town with carby cleaner in the engine bay looking for leaks.

Any help would be appreciated :)

Thanks all
- Ash

 

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Last edited by Hybrid34 on Mon Jan 20, 2014 9:27 am, edited 1 time in total.

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 Post subject: Re: Cold air switches from face to demister under load
Posted: Thu Jan 16, 2014 6:46 pm 
Getting Side Ways
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Also wanted to know what this is for,
it connects into a line and a regulator the front of the bbm and another line into the back of the bbm

Image

 

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 Post subject: Re: Cold air switches from face to demister under load
Posted: Thu Jan 16, 2014 10:14 pm 
Getting Side Ways
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You have a Vacuum leak related to one of the servo flaps in the dash - probably the one that closes over the heater when heat isnt required. Under acceleration the available vacuum is emptied, and it switches
Have you checked out the Vacuum joiner behind the glovebox? - and if you have cold selected and kill the engine, can you hear a vacuum leak at all?

Picture 2 is the BBM Solenoid - switches the air supply to the Broadband Manifold to change the Runner Length on ECU demand
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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 3:59 pm 
Getting Side Ways
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Thanks Nigel for the response
I've taken the glove box out and checked all hoses and all are connected (all in the red)
Unless there are ones hidden in the dash that are not accessible from the glove box area?

The area in the green box has a hissing sound ONLY when the aircon is on (this hissing/whirling noise dissapears under load, when it goes from face to demist), however the hissing noise is not present when the aircon is off.

When I kill the engine with the aircon/cold air on - I hear something close ever so slightly.

Vacc hoses I've Checked:
- All in the pic
- T piece at the back of the fuel rail
- Black hoses coming out of firewall
- Heather tap vac hose
- MAP Sensor
- PCV Valve hose on rocker
- Hose under BBM
- Valve that connects to two vacc lines next the A/C Compressor

Image

Cheers,
Ash

 

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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 4:02 pm 
Getting Side Ways
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Ash. Have you tried swapping out the Solenoid pack there? - The Black box 2 inches by about 6 inches with both wires and vacuum? - Its a frequent fail point. You need to make sure you get the right one though (by part number)
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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 5:50 pm 
Getting Side Ways
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Nigel wrote:
Ash. Have you tried swapping out the Solenoid pack there? - The Black box 2 inches by about 6 inches with both wires and vacuum? - Its a frequent fail point. You need to make sure you get the right one though (by part number)



Cheers Nigel, are you referring to the black box with all the coloured vacc hoses going into it? (the ones that i've squared in red?)

I haven't changed that yet - fingers crossed thats the issue as its easy to fix :P.
I'll head to the wreckers tomorrow and find an identical one by part number and keep you updated.

Thanks again,

Ash

 

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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 5:52 pm 
Getting Side Ways
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Ash. It could also be the other end of those vac lines - under the dash, mostly to the drivers side of the airbox where all of the "servo"s are. Theres one or two behind which you may be able to reach, a dual-stage one for demister, and one or two "under" the heater in the middle of the car. Worth making sure
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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 5:56 pm 
Getting Side Ways
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Ok great, thanks for the heads up.

Apart from dismantling the dash and pulling it forward - wheres the best place to hunt for the ones that could be the culprit

Cheers,
Ash

 

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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 6:04 pm 
Getting Side Ways
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I cant think of any that will require the dash out.
You have climate control - so instead of vacuum running inside the dash you have that Black Servo Pack. The others you should be able to reach. I assume at this point that youve checked in the engine bay and made sure that the two black vac lines go one to the engine (For Vacuum), and one to the heater tap. Actually the heater tap could cause most of your problems. It often comes off
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 Post subject: Re: Cold air switches from face to demister under load
Posted: Fri Jan 17, 2014 6:16 pm 
Getting Side Ways
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yeah was the first thing I checked, heater tap vac line i've had issues before, so ive gone at it with duct tape (not coming off now :) ).

I've also been told it could be that blue/black round thing that is behind the solenoid (behind the washerbottle in the first picture).

Apparently its a one way check valve?

 

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 Post subject: Re: [SOLVED] Cold air switches from face to demister under load
Posted: Mon Jan 20, 2014 9:29 am 
Getting Side Ways
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And we have constant Air!!!

Thanks Nigel for all the help, really appreciate it.

It looks as though it was that blue/black one way check valve.
Upon taking it out and inspecting, it was blowing both ways.

WD40, shaking it vigorously, then tried blowing in and out. The valve now closes off one way.

Cheers,
Ash

 

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 Post subject: Re: [SOLVED] Cold air switches from face to demister under load
Posted: Mon Jan 20, 2014 9:31 am 
Getting Side Ways
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Location: Brisbane
QLD, Australia

Score!. Good work.
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