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Temperature gauge versus OBDII reading.

Discussion in 'VF Holden Commodore (2013 - 2017)' started by Stroppy, May 25, 2019.

  1. Stroppy

    Stroppy Member

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    Okay...this is a weird one. I bought a bluetooth OBDII scan unit that works with an app on a phone. I set it up correctly and everything works fine...the speedo and tacho are true to the dials in the dash, etc. BUT the temperature gauge climbs to just below half way and stays there (regardless of engine load, etc...) whereas the OBD unit shows the temperature climbing to 81% (still out of the red danger zone but I tested this on a cold Melbourne day so I was a bit alarmed). I don't get it... the dash gauge says one thing and the OBDII says something else.

    I have been told that there may be more than one temperature sensor involved in the engine and that manufacturers keep the temp gauge "dumb" (not overly reactive to engine temperature fluctuations) to stop people freaking out when the gauge climbs when they are belting down a freeway or up a hill. Me...I don't know what to think. Are there any tech gurus out there who can advise please? The car is a VF Evoke with the 3L engine. Only done 55,000 km thus far. It is driven sedately, regularly serviced...etc...etc... In fact I have the services done more frequently (and have the synthetic oil changed) to prevent the dreaded timing chain stretch. I treat my cars like gold.
     
  2. Forg

    Forg Well-Known Member

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    Temp gauges in cars are nowhere near linear, they’re designed to only show you if something is way over the top too hot (or way too cold).

    The actual temps of coolant, oil, intake-air etc can be quite different.

    I don’t think it’s anything to be worried about; just interesting info. :)
     
  3. Stroppy

    Stroppy Member

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    Thanks Forg. I was really freaking out about it. Started imagining having to replace the coolant and the thermostat and maybe the water pump. Typical "car hypochondriac." LOL. :)
     
  4. 07GTS

    07GTS Well-Known Member

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    what is the degrees the engine coolant sits at ? u had 81% not sure if u ment 81c deg ?
     
  5. Stroppy

    Stroppy Member

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    I should have looked more carefully but "81" was the percentage it gave. There was a temp reading but I didn't write it down. One thing, though, was that at no time did the OBDII dial go into the "red danger zone". The needle climbed when the engine was working hard and then backed off as the engine slowed. Just to be on the safe side I will ask my mechanic (who is a great bloke and very trustworthy) to change the coolant anyway. Can't hurt. I might ask him to pull the thermostat out and have a look at it as well. They are a cheap replacement part anyway, from memory.
     
  6. 07GTS

    07GTS Well-Known Member

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    sounds like u are looking at something related to temp but not actual temp, the engine temp shouldnt move around that much when driving under normal loads and its never in %, find the SAE ECT readout in deg C it should be about the 90c when at operating temps and anything upto 110c is normal if ur sitting idling
     
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  7. Stroppy

    Stroppy Member

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    I will set the thing up again tomorrow and pay more attention to the temperature and let you know what it reads. Thanks for taking the time to reply...I really appreciate it. I'm buggered now (I'm an old fart) so I am about to have a nana nap on my armchair. Dog is already asleep and dog's dad will be very soon...LOL! :D
     
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  8. vs-lover

    vs-lover Well-Known Member

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    Stroppy, it sounds like you used to own a VR or VS Commodore at some stage as their temp gauges are something of a amusement ride as they continually go up and down if you are not at a constant speed of 60kph. I must admit they can strike the fear of God into you if you're not used to them, but the VF certainly has the temp gauge dumbed down just like you suggested so as not to alarm the driver like they did in the VR~VS vehicles. If I recall correctly changing the Thermostat isn't an easy job in an Alloytec.
     
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  9. Stroppy

    Stroppy Member

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    I did drive my father's old VR Acclaim but never noticed any variation of the indicated temp. I drove a TJ Magna for years and the gauge in that was rock steady...once it reached operating temperature it just didn't move EXCEPT if you did something stupid like I did in changing the coolant without properly bleeding the system... Then the gauge did a foxtrot all over the place until I got all the air out of the system. With my VF the gauge needle will reach just below half way and stay there, rain, hail or shine...but the blasted OBDII was reading differently...it was doing my stupid head in!
     
  10. 07GTS

    07GTS Well-Known Member

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    jap vehicles from the 90's have use dampening for the temp gauge (and fuel) more so then Aussie cars, but now days its all data flowing thru the car and they can do anything with it so they just make it read one position for all the normal driving conditions if it then goes outside that hotter it will first move a little higher just so u notice something is going on then if not fixed and gets worse it will go into the red H to say stop driving u have an issue
     
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  11. Mattricho

    Mattricho Active Member

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    I think @07GTS is on the money with the temp gauge reading normal operating ranges between 90c and 110c.
    To the car this within the normal range so the gauge shows it at the normal setting (just under half way on the gauge)

    I’d say if you where towing up a hill and the temp started going over like 115 or something like that then the gauge would start going up higher.
     
  12. Kingcarl

    Kingcarl Active Member

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    Hahahahaha what a ride!
    I miss the simplicity of those VR VS days you have bought back some funny memories. I had a ss cold air intake on mine and on a cold night cruising it would drop to C, or in traffic the gauge would go up and down with the thermo kicking in and out.
     
  13. abuch47

    abuch47 Active Member

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    Just to piggyback whats a good obd2 reader/scanner to use?

    already have the torquepro app.
     
  14. stooge

    stooge Well-Known Member

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    I use a scan gauge
    https://www.scangauge.com.au

    Ultra gauge
    http://ultra-gauge.com/ultragauge/ultragauge_wired.htm

    EDS
    https://www.4wdsupacentre.com.au/engine-data-scan-computer.html

    All of these are standalone and do not require a mobile app.
    They are also for use while driving.
    if you need one thats for the shed just to read codes than most of the cheap bluetooth ones on ebay that work with the torque app are fine.
     
    Last edited: Jun 2, 2019
  15. Terry57

    Terry57 Member

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    Has anyone one used the American made " Bluedriver " OBD. ?

    I've just ordered one.
     

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