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Heater ducting - what is air route in dash?


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I've had a persistent air problem with my heater since the bulkhead was replaced years ago - heater went from foot-burning to rather feeble. I've done all the cable checking and adjustment as Western has suggested, also had the whole heater assembly out last year and cleaned up (it was fine from the previous removal and clean) and when 12v applied to it the motor was strong and freely running. It went back in and I replaced the bulkead/heater seal and cleaned the intake.

However it still wont shift as much air as before, although it does get hot, but there's a difference bewtween the passenger & drivers footwells output and I'm wondering if there's some blockage or incorrectly fitted pipes in the lower ddash/bulkhead. I know the upper dash vents were badly fitted and I sorted them.

But I'm not altogether certain what the layout is inside the lower dash. Is there a diagram showing what goes on in there - is it piping/ducting or is there simply a hollow section that air is carried through?

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Looking in to mine, it's just an open box with the linkages running across/through it at the height of the lower vents, two bottom vents and two top ones for demisters.

Have you checked the flaps in the lower vents are opening fully? 

What sort of flow are you getting from the top vents?

Edited by ThreePointFive
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48 minutes ago, ThreePointFive said:

Looking in to mine, it's just an open box with the linkages running across/through it at the height of the lower vents, two bottom vents and two top ones for demisters.

Have you checked the flaps in the lower vents are opening fully? 

What sort of flow are you getting from the top vents?

Well to be honest its a bit feeble from the top vents.

I'm just curious whether there's any obvious duct connection that might have slipped apart - there seems to be enough warm air, its just all in the back of the dash and not getting out.

The flaps work - I can pull the lever and with my fingers in the vent can feel the flap closes/opens.  If the fan switch is maybe on the way out would that cause a reduced 'blow' rather than it being a problem of reduced flow? (basically the fan works, the airway is clear but the motor controller is errant?)
 

46 minutes ago, western said:

Lower dash is hollow with 2 connected flaps to feed air to footwell, there is a diagram in parts book in cooling & heating section IIRC. 

Thanks Ralph, I'll have a look - ok its Page 429 in the manual I have and I already looked at it but missed the point that it was a hollow section! I was trying to find something showing actual pipes/tubes! Doh!

Edited by Jocklandjohn
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5 minutes ago, Jocklandjohn said:

Well to be honest its a bit feeble from the top vents.

I'm just curious whether there's any obvious duct connection that might have slipped apart 

There is a short hose on each side connecting the lower dash to the top vents. They just slip on with no clamps.

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Thanks lads -  think I need to start at the heater unit again and work back through all the bits and just check all is as it should be. At least I know now that the main transverse link is a hollow section rather than some wildly routed serpentine pipework - thats a great help!

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59 minutes ago, Mo Murphy said:

Lack of demist flow can be just the convoluted tubing slipping out of its rubber tube at the bottom so it warms your gauges up nicely.

Mo

Thats precisely whats happening at top. I can see some dash removal in my near future!

Thanks!

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For many years, since I replaced my bulk head, my airflow has been asthmatic as an elderley ant! 

At the start of lock down I stripped the dash off and added a couple of small PC fans just below the demister ducts to turbo boost flow upwards. See the photos - the white padding is some hydrophobic insulation and sound absorbing material.

I also added some seals to the lower vent flaps (bits of neoprene but might rip them off and replace with sponge draft excluder instead). I cut the seal for the passenger lower outlet to restrict air flow so that more is directed to the driver's side.

I put it all back together and the difference is significant. I now get a good strong blow to the demisters, on both sides.

 

 

image.png.719fb42630642ce069f9e8c9fd3732fd.pngimage.png.1b2ff87fb3921dac0f7efd207d774bd8.png

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Good use of old computer parts there! 

13 hours ago, fearofweapons said:

For many years, since I replaced my bulk head, my airflow has been asthmatic as an elderley ant! 

At the start of lock down I stripped the dash off and added a couple of small PC fans just below the demister ducts to turbo boost flow upwards. See the photos - the white padding is some hydrophobic insulation and sound absorbing material.

I also added some seals to the lower vent flaps (bits of neoprene but might rip them off and replace with sponge draft excluder instead). I cut the seal for the passenger lower outlet to restrict air flow so that more is directed to the driver's side.

I put it all back together and the difference is significant. I now get a good strong blow to the demisters, on both sides.

 

 

image.png.719fb42630642ce069f9e8c9fd3732fd.pngimage.png.1b2ff87fb3921dac0f7efd207d774bd8.png

 

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