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Temp Gauge 2004 4.9

Discussion in '1994-2004 V6 Mustang Tech' started by dirk, Oct 20, 2019.

  1. dirk

    dirk New Member

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    High everyone im just new today. I just purchased a 2004 3.9 Conv. Everything seemed fine until I noticed my temp gauge don't move. I ghanged the cylinder head sensor but no luck. I don't have any codes up. I have heatand the cooling fan kick off an on.Im starting to think I might be the stepper motor in the gauge. Any body out there got any ideas Thanks for any help Dirk
     
  2. Pete fender

    Pete fender Pete Fender

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    Check all of you fuses.
    The temperature gauge on the 99-04 is really not accurate.
    They only read a bit above nothing, and if it gets hot, it will peg the needle.
    In 20 years since I bought mine new, I have never seen the needle stay in the center.
    It's more or less a glorified idiot light.

    By the way, where is your sensor?
    Mine, a 2000, is next to the heater supply pipe, the one with the coolant air bleeder.
    After 2001, some are in different places.
     
  3. fasterthanyou

    fasterthanyou Active Member

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    I would check with a scanner to see what the coolant sensor is reading. If the coolant sensor is providing relevant data then I would assume the gauge is defective. However, I don't believe I have ever seen a defective coolant gauge but I suppose anything is possible.
     
  4. dirk

    dirk New Member

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    Mine is on the back of the drivers side head
     
  5. dirk

    dirk New Member

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    I was told at the ford dealer that the 2004 3.9 don't have the coolant sensor it is all run buy the cht sensor.
     
  6. fasterthanyou

    fasterthanyou Active Member

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    Pretty sure they are incorrect about that although my only experience is with 96, 99 and 2000 3.8's. I doubt they would suddenly get rid of the coolant sensor in the intake manifold but I could be wrong
     
  7. Pete fender

    Pete fender Pete Fender

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    Before 99, some Mustangs had two sensors, one for the gauge and one for the fan.
    99 on up, there is only one, but in some years they were in different places.
    Some were in the rear of the block on the driver side, if you have one there, you MIGHT have one in the front.
    My 2000 has a two wire plug, and controls both the fan and gauge by way of the PCM.
    The most common place is the front top of the lower manifold near the heater tube that has the bleeder valve.
    My 2000 has it there, and two drilled round flat spots.
     
  8. dirk

    dirk New Member

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    I have nothing up by the heater tube,just the one at the back of the drivers head. When I do a search for the coolant sensor it look just like the cylinder head sensor. The car is running fine no codes come up.Is there a place where I can ron a mechanical gauge Thanks
     
  9. Pete fender

    Pete fender Pete Fender

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    You can drill and tap the manifold where the water crossover is.
     
  10. dirk

    dirk New Member

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    Hey Pete I got another cluster from a scrap yard for 30 bucks. I do dealer trades for a ford dealer an my buddy is a mechanic out in the service. He told me to have my cluster ready to come out an bring it up to him an he will swap it out and do a PMI on it to transfer everything from mine to the new one. That way my mileage keys and everthing will be the same.Ive restored 5 Chevys and this is my frist Mustang and im complety in the dark. Thanks for ur help
     
  11. fasterthanyou

    fasterthanyou Active Member

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    Yeah ford engineers integrated the anti theft system with the cluster for whatever reason which requires the PCM to be flashed to match the vin, PATS and mileage with the vehicle computer when the cluster is replaced. Most shops charge 100 bucks to do this so it's cool your buddy will do it for you.
     
  12. Pete fender

    Pete fender Pete Fender

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    I see a lot of gauge clusters for sale on ebay, but you do have to re-flash so your key matches.
    I think if you do like you say, swapping the PATS unit inside the cluster, you should be OK.
    Pats should remember your mileage, it is in memory in the PCM, as is the key.
    The PCM and cluster have to match, or you'll have to re-flash the PATS unit.
    Here is a link explaining what makes PATS work, including pictures of the module that is most important.
    It also states the the key code is not stored in the PCM, which is different than A PCM reprogramming company told me.
    Good thing it was just a broken wire, or I would have spent over $200 on nothing.
    Some PATS are in the cluster, and some are stand alone.

    Ford PATS Antitheft System — Ricks Free Auto Repair Advice
     
    Last edited: Oct 22, 2019
  13. dirk

    dirk New Member

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    Thanks guys I will let u know how it works out. Im still going to put a set of mechincal gauges in just to be on the safe side Thanks Dirk
     
  14. dirk

    dirk New Member

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    fasterthanyou if theres a coolant sensor on the 3.9 where is it located
     
  15. fasterthanyou

    fasterthanyou Active Member

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    Mustang: The location of the engine coolant tempature sensor…

    They provided images here. Like I said I'm my post above I wasn't exactly sure where. I ended up googling 2004 3.9l mustang coolant temperature sensor location and found dozens of posts from various forums of people asking the same question. 01-04 just had one sensor and it's in the head. Basically everything pre 01 was in the intake manifold.
     
  16. Pete fender

    Pete fender Pete Fender

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    Yeah, mine is on the lower manifold, next to the heater pipe, that has the cooling system bleeder plug on it.
    I wish I knew why they kept moving the sensor around, it was not a new engine at the time.
    The F150 and Windstar had the dual port a few years before the Mustang did.
     
  17. dirk

    dirk New Member

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    Well I changed the cylinder head sensor and the thermostat and today I had the cluster check out from a place that repairs speedo. The cluster is good so its not the gauge. I asked my buddy whos a ford mechanic and he say it must be in the PCM. Hes going to check it out for me . will let u guys know what happens Dirk