No fan ?

Discussion in 'Kenworth Forum' started by A- Model, Oct 21, 2017.

  1. A- Model

    A- Model Bobtail Member

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    Oct 18, 2017
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    hey everyone, newbie to the site with a question I'm sure you've already heard a million times in one form or another but this is driving me nuts. I have a w-900 with a cat 3406e 2ws. Engine fan will not come on when supposed to while climbing a hill or when engine reaches temp. I've always turned it on manually. I do all my own work but can't figure it out. Replaced temp sensor on front of thermostat housing because I just assumed. (Know better) Temp gauge is manual type so I checked this in a pot of boiling water with another thermometer beside it, both read about 1 or 2 degrees apart. Temp gauge is correct. Can't see any pinching or damage to wire harness. So took truck to kenworth, they're telling me that gauge is wrong but ecm is reading correctly. Fan does come on but the problem is the temp gauge says 230 degrees. I know that the temp gauge is correct because I checked it, and the shop mechanic looked at me like I was lying which pissed me off. One of these sensors is not right but which one. If the eco was bad wouldn't they be able to see this?
     
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  3. snowwy

    snowwy Road Train Member

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    Don't know if your truck has it but i've had 3 different trucks that wouldn't kick the fan on. Problem was the solenoid. I think it's called. I beleive it's supposed to release the air and the fan kicks on. And you might have more then 1 sensor for temp. 1 for gauge and 1 for ecm which should kick the solenoid on. For example.

    I drive an 07 w9 with c15. It shuts down at 230.
     
    Last edited: Oct 21, 2017
  4. strollinruss

    strollinruss Road Train Member

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    I've his problem too. I watch the temp gauge and just flip it on.
     
  5. kwcam

    kwcam Light Load Member

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    At the bottom of the thermostat housing facing the rad is a two wire sensor, this is the temp sensor that the ecm reads, if you unplug it the ecm reads a default temp of 190*f and fan will run constantly. I would replace this sensor first as it is not reading the same as your manual gauge.
     
  6. A- Model

    A- Model Bobtail Member

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    Oct 18, 2017
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    Thanks for the replies, haven't figured this out yet but working on it. Have a friend at cat that's been doing some research for me too. He's telling me that there is another relay that's buried in wire harness in the dash in these kw's. Haven't found this yet just wanted to pass this along, I'm just getting home after being out 3 was so ill get on it monday.
     
    Oxbow Thanks this.
  7. Oxbow

    Oxbow Road Train Member

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  8. spsauerland

    spsauerland Road Train Member

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    Fan will be programmed to come on @ 217 for coolant temp. Need to check into your coolant temp oem sending unit, wiring, and gauge.
     
  9. bigguns

    bigguns Road Train Member

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    Would a bad connection at the high and low ac pressure sensors keep the fan from coming on. Are you getting juice to the air solenoid telling it to turn fan on? Does the ac cause the fan to come on as it should? Check the coolant temp at the sensor to see if the fan does indeed need to come on. Block off the air to the radiator. Run the engine up to a high idle. check your ac pressure and see if the fan comes on. read the coolant temp at the sensor(s) to be sure they are reading correctly. Does it even have the right fan temp sensor in it? A NO sensor where a NC sensor should be or the reverse scenario.
     
  10. spsauerland

    spsauerland Road Train Member

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    High and low pressure switches are for controlling a/c compressor thru a relay. Separate pressure switch for a/c high pressure in fan override circuit. His fan does work, but it seems to be kicking in at a temperature higher than 217. Someone with Cat ET showed him that cat coolant temp sensor and gauge not reading the same. Needs to verify which one is reading correct with infrared temp gun. My bet is problem with KW side, not Cat side.
     
    Oxbow Thanks this.
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