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75 Bay heating system – blowers, tubes, ducts etc

Discussion in 'Bay Tech Clinic' started by Micky O, Jul 27, 2018.

  1. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    Righto folks, with this often chilly winter mountain weather, I made an executive management decision to get my heating and de-misting system working better in my 75 Bay 2L Microbus. I have investigated all over the interwebs and there is some confusion out there. Some questions so far:

    1) Blower fan above engine - is this supposed to kick in automatically after the engine warms up as part of the engine cooling system? (Some sources say it is automatically controlled by a thermostat, but where/how/what is a mystery to me.) If so, that would make the LH red lever on the dash control simply whether the warm air is blown outside or inside the vehicle (as per this handy diagram http://myweb.tiscali.co.uk/freemefromthishell/vw/T2 Heating.htm ).

    2) Which fan or fans are designed to be operated by the knob on the dash? On my other Bay, a 76, both the rear and front blower fans are switched on by this knob! - but on my 75 it seems only the front fan. (Which sounds like a klaxon btw, so that's something else to look at.) Is the front fan designed to blow either hot or cold air, or is it just a cooling fan as some on this site have previously suggested? Is the rear blower (when actually working) strong enough on its own to send a decent stream of hot air all the way through the system?

    3) Ducting - some of the hot air ducts are shot and need replacing. Fair enough, and that helps explain why hardly any heat reaches the cabin. But (see pics) has anyone seen these thick fabric shrouds over some of the main ducts and joints before? Are they original? Are they of any use? Are they full of asbestos?

    20180727_110454.jpg 20180727_110332.jpg

    And this third pic shows how the main duct is squished into the space above the front axle - surely this constricts hot air flow? Someone tell me it aint right and it should be suspended below the axle.
    20180727_110442.jpg

    4) If the RH lever switches hot air between feet/de-mister, is there no control over the other heat outlets - the one below the middle seat (where there is an elbow for an absent heater) and the rear-facing vents on the floor between the two bulkheads?

    5) Do I need to source proper VW concertina ducting or is the Repco stuff OK? (presuming they have the right sizes.)

    Thanks for whatever advice you can give me. Mick
     
  2. paul77

    paul77 Well-Known Member

    Messages:
    926
    Location:
    Brisbane
    Can't answer all your questions but on my 77 bus the rear fan above engine operates when demist position of dash lever selected. There is no thermostat in place afaik. General cabin heating occurs (without that rear fan) as part of air from engine cooling fan is pushed through heater boxes towards front of bus. The only front fans I am aware of are those 2 ambulance fans? located in the fresh air ducting near cab doors. The fresh air and heating systems are isolated from each other.
     
  3. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    Ta. I now realise some of my terminology was slightly confused. It's the normal engine cooling fan which does most of the pushing of heat around.

    The fan above the engine is the heater 'booster' (or 'supplementary') fan. You're right, in my 76 that booster fan only comes on if both heat and de-mist red levers are selected. It would be nice if it came on to heat your feet, but we can't have everything.

    It may be the same in my 75 ... I just can't get the booster fan to work at all. And there's so many other gaps in the heater tubes that the entire heating system is a bit useless...
     
  4. Mordred

    Mordred Super Moderator Staff Member

    Messages:
    2,672
    Location:
    Penna, Hobart
    The booster fan is a special beast. It has a relay that only comes on once the alternator is charging the battery, so normally doesn't work unit a few mins after startup. Also it is activated by the heat lever only as there is a contact behind the cluster that makes when the lever is in the last bit of travel.

    Start at the main cooling fan, make sure the 2 flaps in the bottom of the fan housing are opening and closing properly. Make sure the covers are on top of that little duct to make a good connection. Make sure the heater valves are opening fully. The cables will stretch and need adjusting or replacement. Check the flap are moving the other valves further down which allow heat into the cabin. If it is a microbus it will have another to feed heat out through the floor to the back seat. The last valve is the one to feed air out the vents near your feet or up on the windscreen. Make sure that cable is adjusted too.

    If all that is right you should only need the booster at low engine revs to increase the heat a little. It was never designed to increase the heat through put at highway speed.

    Hope that helps a bit.

    Adrian
     
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  5. Wayne murray

    Wayne murray Well-Known Member

    Messages:
    1,880
    Location:
    Seven hills
    The insulting material is original material.
     
  6. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    That is good to know. I suspected as much. I will wear the safety gear when removing it, as gawd knows what's in it.
     
  7. Andy.

    Andy. Active Member

    Messages:
    439
    Location:
    Brisbane
    As others have noted, one lever selects heat on (opens both flaps at the heat exchangers at the engine), and at full travel turns the fan on. The other lever selects between heating the cabin and demisting. Looks like you have heating to the middle row outlets, this is closed for demisting also. All up two lever, but 4 cables.
    In practice the fan only boosts air flow at low revs, at higher engine speeds the engine fan will push more than the booster fan (flap valves in booster fan close it off)

    Replacing the ducting is best to get something insulated to get the warmest air to the front. The common VW paper/aluminium hose is not, so check what your getting. I did mone years ago with a thich rubber hose and has worked well.

    The extra outlet for the rear most seat is a hole under the middle seat, originally there was a spreader under the middle seat for this. That junction is controlled by the one cable when you turn the demister on.

    Great system when working, but outside of QLD and NT they struggle.....
     
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  8. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    Thanks, a good description Andy. Yes, mine would have had a spreader under middle seat, but I'll probably close that hose off as I don't have the spreader thing any more ... unless anyone knows where to get one :D. Good to know about the double cable action of the de-mister lever - no one anywhere has mentioned that before! - so the cables are making more sense now. Just gotta get em working ...
     
  9. Andy.

    Andy. Active Member

    Messages:
    439
    Location:
    Brisbane
    Don't have photo's of mine (too long ago), and the bus is in storage at the moment, so not easy to get pictures.
    If you get to working on it and send pics, I should be able to give you pointers.
    I have a spreader bar, but it's staying in the bus :) The other thing most are missing is the hole in the floor had a spring loaded flap. Probably the US (Samba?) would be a good place to look for bits as I have not seen many here. It bolts down with two of the rear seat mount bolts.
    Cables are available new, but the tubes are attached to the body. I cleaned mine out fine, but if they are very rusted, might be easier to run new cable outers.
     
  10. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    Yeah I still have a fully functioning springy flap for the middle spreader, so that's something. If I ever get a spreader I'd just have to cut an extra hole in my new rubber floor.

    Cable tubes look OK. What did you use to clean them out?

    Cables are moving OK at the lever end, but there's no corresponding action at the flap ends. The flaps themselves seem OK, I can wiggle em open and shut ...
     
  11. 76kampa

    76kampa Active Member

    Messages:
    117
    Location:
    Perth
    The front fans are just the air conditioning (vent fans) the only heater fan is the one in the engine bay which was missing in mine lol
    I have bought a heater fan now but have no hose, but I only need one as someone has blocked off the left side heater box as they installed a oil cooler that is in the way.
    None of my heater cables work so I would have to wire up the flaps to get any heat.
     
  12. Andy.

    Andy. Active Member

    Messages:
    439
    Location:
    Brisbane
    I had my bus back to a bare shell, so I just over a few days put kerosene down them and blew out with compressed air. Once free, I got the old cable and shoved a small piece of rag (soaked in kero) down the tube. Don't make the rag too big, you don't want it stuck 1/2 way along the tube. If you get movement one end only, chances are cable is snapped or rusted through somewhere along it's length.

    I left my system stock and works well (for Brisbane). I know a lot of people in the US messed with many idea's to improve the system. The good factory solution of course was the additional petrol fired heater (Eberspasher)
    I think for out climate (maybe not for the snow) additional booster fans would get it working well. You can get now nice inline/axial fans that could fit into the heater hose and boost the flow. The problem is they would be in the heated air.
    In the air cooled T3's they used a booster fan running off the engine. Not sure how well they worked though.
     
  13. AC-T3

    AC-T3 Well-Known Member

    Messages:
    834
    Location:
    Woy Woy
    Real good. Even in the dead of winter it only takes a few minutes for hot air to circulate. The "booster" is attached to the alternator pulley.
     
  14. Grantus

    Grantus Well-Known Member

    Messages:
    14,495
    Location:
    Southern ACT
    Dead of which winter? o_O

    Central Coast winter? :rolleyes:

    About as cold as a warm spring day elsewhere.....:p
     
  15. Wayne murray

    Wayne murray Well-Known Member

    Messages:
    1,880
    Location:
    Seven hills
    I think it means in the middle of winter when it is meant to be the coldest, shortest hours of light. or Siberia winter perhaps.:eek:
     
  16. AC-T3

    AC-T3 Well-Known Member

    Messages:
    834
    Location:
    Woy Woy
    Yep, thats about average here. But bus has been known to wake up in some places with wipers frozen solid to the windscreen covered in sheet ice - heater and de-mister still worked good there too.
     
  17. Andy.

    Andy. Active Member

    Messages:
    439
    Location:
    Brisbane
    Out of interest, when I re-built my engine, I had the piston crowns and heads ceramic coated. I did the same to the (outside) of the heat exchanges and did notice and increase in heat to the front.
     
  18. KateTheKombi

    KateTheKombi New Member

    Messages:
    1
    Location:
    Brisbane
    The original insulating material like you have in picture is asbestos
     
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  19. Micky O

    Micky O Member

    Messages:
    79
    Location:
    Blue Mountains
    Yeah that was my suspicion ... gonna have to wear a space suit!
     
  20. 1500king

    1500king Well-Known Member

    Messages:
    1,532
    Location:
    Adelaide, SA
    Of course! It kept all the heat in the motor!.. lol!
     

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