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Thermo fan T3

Discussion in 'T3 & T4 Tech Help Clinic' started by Greg N, Jan 20, 2015.

  1. Greg N

    Greg N Member

    Ok, I'm having a problem with the thermo fan not operating once the temp passes the half way position on the guage and the led begins flashing. I replaced the thermo switch in the radiator with the correct part and no change.
    I have just tested the fan by direct wiring it and it's fine. I have tried changing the relay, no change, I have checked and cleaned the earth where it attaches to the earth tree and it's fine. Fuse is fine and the red led continues to flash at me and no fan. Grrr!
     
    Last edited: Jan 20, 2015
  2. Grantus

    Grantus Well-Known Member

    Messages:
    18,622
    Location:
    Southern ACT
    Is there a working 30amp fuse in position 1 of the fuse box? (Closest one to the LH door) :rolleyes:
     
  3. Greg N

    Greg N Member

    I just looked and it is a white 8amp fuse there, I changed it to a 25amp just to check. That's the highest amp fuse I have and no change. I get a short burst from the fan, but the light continues to flash and the temp foes past the half mark. Can of petrol and matches are close by
     
  4. Greg N

    Greg N Member

    The only option I can think of trying now is to go to a lower temp switch. The current one and the original are 95 and 102 degrees. I think there is a 75 degrees switch available
     
  5. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    7,046
    Location:
    Gosford
    I thought you were going to get a new sensor, the one that screws onto the radiator.
     
  6. Mellow Yellow 74

    Mellow Yellow 74 Active Member

    Messages:
    847
    Location:
    Sydney
    My understanding is that the flashing light is coolant level warning not coolant temperature warning - check your coolant level.
     
  7. Greg N

    Greg N Member

    Yes, I have bought a new switch, it is the large screw in thermo switch that activates the fan. It screws into the lower right hand side of the radiator behind the lower grille. The coolant level is fine, I think the flashing led does have two purposes, low coolant warning and high temp warning.
     
  8. Grantus

    Grantus Well-Known Member

    Messages:
    18,622
    Location:
    Southern ACT
    Correct, (from personal experience), there is some clever electrickery, that makes the light flash in 2 different modes - low coolant and /OR high temperature..;)
     
  9. Grantus

    Grantus Well-Known Member

    Messages:
    18,622
    Location:
    Southern ACT
    Isn't it one and the same with the switch? :rolleyes:
     
  10. yeah fan should be coming on way before light starts flashing (both speeds I think)......not sure if the dash pod electronics may be your problem?
     
  11. Greg N

    Greg N Member

    Oh ok... I didn't realise that a problem with the dash pod could cause issues as well. Oh god, I just hope a lower temp switch may work
     
  12. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    7,046
    Location:
    Gosford
    There is always the Gowesty hard wiring kit for the dash pod to replace the blue plastic harness
     
  13. Greg N

    Greg N Member

    Hopefully I don't need one of those Phil, I'll wait until tomorrow and if I don't get any other clues I'll try a lower temp switch and see what happens.
     
  14. syncro

    syncro Well-Known Member

    Messages:
    10,288
    Location:
    Southern Highlands
    Is it actually getting hot?
    It could be the low coolant sensor. Try cleaning it.
     
  15. Grantus

    Grantus Well-Known Member

    Messages:
    18,622
    Location:
    Southern ACT
    Good point, and easiily done.

    Carefully unscrew from the top of the coolant bottle, clean the prongs, but don't overtighten when refitting to the pressure bottle, as they are both plastic threads, and eeasily damaged.....;)
     
  16. Greg N

    Greg N Member

    The temperature is getting higher then it normally does yes, but only when sitting in traffic. I'll order a new coolant sensor as well, it appears to be the original, so wouldn't hurt to change it anyway.

    Damn electrical gremilns :mad:
     
  17. syncro

    syncro Well-Known Member

    Messages:
    10,288
    Location:
    Southern Highlands
    Sometimes when you change these sort of things you take out a good quality working part and replace it with a short lived poorly made part. Many Kombi owners have done this with coils.
     
  18. Greg I would have an original working 2 stage fan switch here somewhere if you would like to try another.
     
    Greg N likes this.
  19. Greg N

    Greg N Member

    Thanks mate, I've got another thing to try tomorrow morning. I have just been onto the Vanagon Owners page on Facebook and another guy thinks the symptoms I mention could indicate air in the system... I'm not sure how considering I changed the coolant 18 months ago and it hasn't been an issue until recently. I'll bleed it again tomorrow though. Any thoughts on this?
     
  20. Grantus

    Grantus Well-Known Member

    Messages:
    18,622
    Location:
    Southern ACT
    Air in the system will do that..... but only if there is enough air in the coolant pressure bottle, to expose the coolant sensor.....

    ie, if the coolant bottle is full, any air pockets in the rest of the system, won't trigger the red lED flashing low coolant light.
     

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