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Help please temp guage

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by martyj200, Jan 24, 2014.

  1. martyj200

    martyj200 Member

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    HI all
    I have changed my thermostat when having my temp gauge only reaching 70 (i got the thermostat from GSF car parts)
    Temp seemed fine for a while then started playing up again, i have since replaced the rear temp sensor and things were fine for a little while again ( temp sensor also from GSF)
    I have just this week bought and fitted audi genuine thermostat and temp sensor and if i have my heating off the temp will get to 90
    when i turn the heating on it starts dropping???
    any suggestions folks?
    thanks
    Martin
     
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  3. hades-

    hades- Yorkshire & Humber Rep.
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    faulty gauge
    air lock
    heater matrix blockage
    was it the temp sensor on the engine you changed or the 1 on the rad ?

    aldo you could scan for fault codes with vcds etc.
     
  4. martyj200

    martyj200 Member

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    Hi bez101
    thanks for reply
    yeh it was the temp sensor on the engine i changed.
    I have a feeling it might be an air lock, heater matrix blockage.
    do you have any idea how to tackle this?
    cheers
     
  5. hades-

    hades- Yorkshire & Humber Rep.
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    mine was suspected to be blocked so we took inlet and outlet off the matrix and ran water through it
    it was partly blocked so we blasted air and loads of water after a while it unblocked
     
  6. Mike B

    Mike B Well-Known Member

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    If the heater works and the engine warms up quickly and doesn't overheat everything is OK apart from the gauge
     
  7. martyj200

    martyj200 Member

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    I have just been out for a drive and have noticed....
    when temp fuage is sitting at 90 and i turn the heater on hot, the temp gauge starts dropping.
    If i then turn it to cold it starts creeping back up to 90.
    and its also stays at 90 if the heater unit is off.
    the hot air blower blows hot air and doesnt take too long from start up to blow good hot air.
    it seems as though the temp gauge will only go funny when hot air is blowing???????????
     
  8. yendall24

    yendall24 Member

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    hi mate its possible you do not have a problem . you dont say what engine is in your car but if it is a diesel then you have got the most thermally efficient engine there is also its cold outside so when you are driving your engine radiator is battering through freezing air then you put your heating on in the car then in effect you have 2 radiators extracting heat from your coolant combine this with a very efficient diesel engine and theres your issue . totally ignore everything i have said if its a petrol engine
     
  9. martyj200

    martyj200 Member

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    Yeh mate it is the 1.9 TDI 130 engine
     
  10. martyj200

    martyj200 Member

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    is it normal for this car not to stay at 90 when it reaches it regardless of outside temp and heater blowers?
     
  11. yendall24

    yendall24 Member

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    mine does exactly the same if i have the heating on full inside the car i have the exact same engine as you
     
  12. Mike B

    Mike B Well-Known Member

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    My 2.5tdi just stays on 90.The gauge isn't meant to be accurate just to warn if it overheats.Isnt there another way of checking the temp using the display?
     
  13. yendall24

    yendall24 Member

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    if you are blasting down the motorway then it will stay at 90c regardless of your heater setting once everything is hot when i say hot i dont just mean temp at 90c i mean fully hot ie engine oil hot car engine being held at high revs then the temp should stay at 90c . but if you are pootling around town on a cold day stop start then it will struggle to hold 90c . its all about energy/heat being produced so if you are burning diesel on a run then it will be ok
     
  14. yendall24

    yendall24 Member

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    i believe you can display the temp on the aircon unit not sure what you have to press someone will be along to tell us shortly
     
  15. martyj200

    martyj200 Member

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    If the temp gauge is not registering at 90 when the car is hot and been running for say an hour, will this not affect the fuel consumption?
     
  16. Mike B

    Mike B Well-Known Member

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    No its just a gauge and doesnt control anything.If everything else is OK its just a nuisance
     
  17. bradh

    bradh Active Member

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    mine does the same as this takes about 20 min of constant driving for it to reach 90 and stay there as said above these engines are very well cooled and with the cooler temps out side it will take even longer to get up to temp

    also i once brought a cheep stat and the temp never worked quite right i fitted genuine vw/audi stat and it worked spot on from there on
     
  18. Issac Hunt

    Issac Hunt Active Member
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    Surely if the engine is over cooling then the ecu will inject more fuel since it thinks the engine is cold . I know the gauge doesn't control anything but the temp sensors that sense the temp of the coolant certainly do control other things.

    Mine drops to 70 in traffic and when you put the heater on, it's my only audi to do this and it's deffo faulty. It's in with audi next week for repair.
     
  19. stu_m

    stu_m Well-Known Member
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    mine takes forever and a day to get to 90 but once its there it stays there unless I stop in traffic and have the heating higher then about 22 - 23 then it will eventually drop a little but never as low as 70

    these diesel engines takes ages to warm up in this cold weather due to the fact that they are really efficient

    I can take the missus to work in stop start traffic about 8 miles and takes a good 25 mins and it gets to between 70 and 90

    the cold air on the front rad wont make a blind bit of difference as the stats job is to keep hot water in the engine and not let it flow to the front rad

    the first port of call for any hot water though is the heater matrix to heat the cabin running with the heating off allows it to heat up quicker

    take your car for a decent drive down a motorway to warm it up with the heating off once it gets to 90 turn the heating on and see if it stays there if it wont reach 90 down a motorway within about 10 miles you could have a lazy stat......its not uncommon for a stat to be faulty from new
     
  20. PetrolDave

    PetrolDave Well-Known Member

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    VAG Group water temperature gauges do not display the actual water temperature, if the actual temperature is within a few degrees either way of 90 then the gauge will display 90 anyway, only if it's significantly different from 90 will they display a different value - to stop customers complaining about small, and unimportant, changes in water temperature.
     

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