Airbox

[Big_Richard]

I know what he's talking about regarding acrobatics.

Its very uncomfortable doing anything under the dash with the front seats installed unless you are a very good contortionist. The window of opportunity to achieve anything is very narrow, until the pain becomes unbarable - sometimes its instantaneous

[WGB]

Can I ask some questions.

1) how many flaps are there in total

2) How many of these  rely on foam as the hinge .

3) how many with hinges are stable in respect to the levers without re-foaming.

The reason I ask is that obviously my foam hinges in the main flaps are gone because my levers were jammed
but the system works beautifully summer and winter with the 10 mm nut flap tension eased.

There is a rattle from the system on big bumps but not enough symptoms to make me rip my entire dash out.

Bill

[Big_Richard]

in the air box, there are 7 flaps, 6 are foamed, one central face vent is rubberised and doesn't fail, only 2 are foam hinged.

the foot/left right face vent box there are 2 flaps, (re-foaming these will achieve VERY little)

in the fan motor assy, there is the recirculate flap and the fan shut off flap. (re-foaming these will achieve little)

When i have my box back together I'll have a better idea of if its possible to repair anything without disassembly, TJ has pulled his box also, perhaps he will know more. I wouldn't specifically go in there to pull it when you've a functional AC and good interior, you may live to regret the decision, its something to do "while your in the area" 

[WGB]

Thanks for the detail.

I still have the option of the "Bentley" Technical Publications Article which shows removal of the pair of hinged flaps being removed and then held in place with a pair of springs.

This requires only removal of console and partial removal of the bottom of the heater with removal of flaps and drilling of a hole in each to take the spring.

This is looking a much more attractive proposition.

Bill

[Big_Richard]

that sounds like a very clever alternative with the springs.

I have just done a mock assembly of my air box, and made some final adjustments so it fits together properly.

the a/c coil is inserted with aircon grade foam rubber tape sealing it at the top and each side is sealed with bitumen tape. The only way for the air to go, is thru the coil now. The bottom 2mm underneath the coil is to be kept clear for drainage purposes.

the heater flap assembly then gets inserted on top - I noticed the reason for the cut outs in the top flaps now, because the one on the drivers side will ever so slightly foul on the copper pipework for the coil without the cut out. This isn't one of the foam hinged flaps. I have foamed over the complete flap and with the metal cut out there the foam moves smoothly over that section of copper.

The heater coil then gets inserted into the heater flap assembly - the heater coils outer edges are to be installed with foam seals so as to force all available air thru the coil.

The defrost and front centre vent unit then goes on, then the foot/side vent unit after that.

This is a mock assembly as i still haven't obtained the non hardening sealing putty required to assemble the thing so it doesn't leak condensate everywhere. everything however, moves perfectly and looks as it should. I will go hunting for the putty today, but i don't like my chances.

[Big_Richard]

airbox is now assembled.

have done a test run with the fan motor attached on the living room floor, powered by 2 battery chargers.

in full speed mode, and the fan output flap in the sweet spot, IE, central, the centre vent blows my hair around to show the receding hair line. The side vents do exactly the same, but with even more force. This is clearly how it should be. Bearing in mind though, the fan never gets to full speed unless in "DEF" mode anyway and this was a bench test.

[koan]

in full speed mode, and the fan output flap in the sweet spot, IE, central,

Don't understand, what is and what controls the fan output flap?

koan

[another sad 280s]

the foam output flap is the flap from the fan to the box. it's controlled by the cable on the fan speed switch (from memory). means that no air can be flowing through the box when the air system is off.

[Big_Richard]

I agree 100% with sad 280.

Luckily TJ came around and allowed me to mollest his 6.9, I discovered that i had the flap installed backwards in my fan motor housing. I wanted to double check before riviting it back together and very glad that i did now, Cheers!

[koan]

the foam output flap is the flap from the fan to the box. it's controlled by the cable on the fan speed switch (from memory)

OK, so the amount of air through the box is determined by blower speed and flap position, both of which are controlled by the one knob?

So there is no airflow through the heat section with blower off but the face level vents still let fresh through, and cooled air if the compressor runs with fan off - I suspect it doesn't.

Why is there a "sweet spot"?

Can cooled air come out of the heater/demister in a properly foamed system?

koan

[Big_Richard]

OK, so the amount of air through the box is determined by blower speed and flap position, both of which are controlled by the one knob?

*** Correct.

So there is no airflow through the heat section with blower off but the face level vents still let fresh through, and cooled air if the compressor runs with fan off - I suspect it doesn't.

*** With a correctly adjusted fan exit flap, there will be zero airflow with the fan in the OFF position, anywhere between that and position I starts the flap opening. The compressor should not be able to be turned on before atleast reaching speed I, thats how mine is anyway.
Why is there a "sweet spot"?

*** An incorrectly adjusted fan exit flap can go beyond fully open and start to close again, its a butterfly valve.

Can cooled air come out of the heater/demister in a properly foamed system?

*** Demister can have heated or cooled air through it, as can the foot/side vents. front central vent is ducted into the evaporator area only, so no heating can come from here.

[WGB]

This bit I have pulled down and fixed in my car.

There are two flaps in the incoming air supply.

1) First is cable controlled and runs off the fan switch.

When the fan switch is at the totally off point it is closed. As the knob is turned it opens via a cable (which is why there is that long white line) and after fully opening you then reach the first fan speed, second speed etc and the fourth speed is defrost.

2) The second flap is vacuum controlled and allows either fresh air or recirculated air ( with some fresh air blending).

This is pulled in when the Blue temperature control switch is turned past the line at about 8 o'clock and allows extra cooling from recirculated air.

It says in the book that Fan position "1" and the temp switch both have to be on to pull in the compressor but mine definitely pulls in with the temp control only which is really useful when cruising down the motorway at speed and the fan decides to go into "squeaky" mode.

The airflow is quite adequate on days other than real Perth heat to run without the fan operating in motorway running.

The system is fiddly but is capable of quite precise and infinitely variable control.

Bill

[koan]

Thanks for the info.

You've probably worked out I'm a bit nervous about this job, especially the dash damage possibility, my dash is in good shape and would like it to stay that way.

I'll try (when I get round to it) to get the unit out in one piece with the dash in place but not optimistic. Maybe separating the bottom section off and removing it will allow the top section to come out without dash removal.

koan

[TJ 450]

I'll try (when I get round to it) to get the unit out in one piece with the dash in place but not optimistic. Maybe separating the bottom section off and removing it will allow the top section to come out without dash removal.

koan

That sounds like a good idea, as vertical clearance is probably the main issue.

Tim

[nathan]

i was talking to our german mechanic yesterday. i was discussing the weekend work on the 6.9 and that the dash was out. he commenced a sentence saying in the 80s when the dashes had to come out they always - and i jumped in and said replaced the flaps! yes was his answer. he then proceeded to scold me for not doing the job this time around on goldie. my defence of not enough time fell on deaf ears! he however, noted that they used rubber for the hinges rather than foam.
nathan