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Thread: Parade - pulling float...unplug fan control????

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    Sergeant Major McSpeed's Avatar
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    Default Parade - pulling float...unplug fan control????

    I'm pulling the sophomore class float for the homecoming parade in two weeks. My truck runs right at the limit kicking the fan on and off right around 220 - 230 degrees. I'm thinking about pulling the plug so it runs all the time.

    Other than some extra fan noise - no down side to that is there?

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    Colonel MarkM's Avatar
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    Not a bad idea.

    Mark
    Heavily Medicated Crime Fighter...

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    If your fan is cycling on and off at 220 degrees you've got something bad in the cooling system. The fan should come on around 220-230 but shouldn't turn off until the engine is down around 180 degrees. Unplugging the fan to keep it running is a stop-gap measure that will get you thru the parade but I'd suggest doing some troubleshooting and fixing your problem. Good troubleshooting flow chart in the -20 manual that you can follow.

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    Sergeant Major McSpeed's Avatar
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    Quote Originally Posted by papakb View Post
    If your fan is cycling on and off at 220 degrees you've got something bad in the cooling system. The fan should come on around 220-230 but shouldn't turn off until the engine is down around 180 degrees. Unplugging the fan to keep it running is a stop-gap measure that will get you thru the parade but I'd suggest doing some troubleshooting and fixing your problem. Good troubleshooting flow chart in the -20 manual that you can follow.
    The only non-new part in the system is the time delay module. I would suspect that is what would not hold it in longer. I thought I read it only locks in for 20 seconds, not to 180. It holds for 20 seconds for sure.

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    Quote Originally Posted by papakb View Post
    If your fan is cycling on and off at 220 degrees you've got something bad in the cooling system. The fan should come on around 220-230 but shouldn't turn off until the engine is down around 180 degrees. Unplugging the fan to keep it running is a stop-gap measure that will get you thru the parade but I'd suggest doing some troubleshooting and fixing your problem. Good troubleshooting flow chart in the -20 manual that you can follow.
    My fan cycles from 225-220, on and off respectively. That's the temp on the gauge anyway. Used to not be so good, but I replaced the gauge and block sensor.

    BDGR

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    As long as you don't end up cooling your engine down below 180 degrees, which is unlikely with a working thermostat in the cooling system, I see no issues with having the fan run 100% of the time.



    I know the fan in mine comes on up around 220-225 on the gauge, and only runs for 20-30 seconds before turning back off, bringing it down to the 215-220 range. Normally sits around 190 or so when not working hard. Not that I trust the gauge to be completely accurate, but as long as the fan kicks on and off I'm happy with it.

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    Colonel Milcommoguy's Avatar
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    The time delay module as noting to do with temperature. It allows for a twenty second +/- window to disengage the fan during;

    1: an attempt to force a down shift (peddle to the metal and kick down switch correct and transmission solenoid does its thing) getting a little more HP out out of the engine to make the shift and get out of it way.

    or 2: when entering deep water by peddle to the metal quickly, fan disengages as not to turn the fan into a propeller with 20 sec to get in the water, should the fan have been engaged. Hit the water running good chance of sending shards of plastic fan parts to the bottom. Once it the water ya need to tippie toe across. HUMMWV fans not know to be very good propellers.

    The temperature switch in the water crossover controls the cycling of on or off. Yes, you can unplug the TDM and run fan continuous. (fail / default mode) any gain is questionable. Let it do its thing IMO.

    Loss of power to the Cadillac valve, fan runs. Assuming all the parts are playing nice.

    Tubro engines can run a bit higher, but should cycle OK. Running at temperature is best for diesels.

    Gauges are slow to react or have a bit of hysteresis and in many cases not known for accuracy. Make a mental note of the highs and low cycles point and that's your HUMMWV temperature health. Anything out of your norm, time to see the doctor. LOL

    Take a lookie here > https://hummerhuren.files.wordpress....iagnostics.pdf < This is the manual that didn't come with these rigs. Answers all the easy stuff for FREE.

    Hope this help. Good luck.

    No hot flashes, running cool, CAMO
    Last edited by Milcommoguy; 09-23-2019 at 14:18.

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    We pulled the plug on the time delay overseas when I was in the military so the fan ran all the time. You’ll be totally fine running it that way. It’s like a fail safe. If that module goes bad, it makes sure the fan runs.
    1989 M998

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    In hot climates it makes sense to operate with either the fan solenoid or the TDR unplugged to keep things cool. In moderate climates leaving the fan operating continuously will cause the thermostat to cycle to try to maintain engine temperature and as long as the thermostat is good you shouldn't have any problems but if the thermostat is stuck open you could over cool the engine and diesels like to run hot for efficiency.

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    Let me reiterate my comment. If his intent is to drive in a parade at parade speeds with the fan running constant with IL’s current temps, he should have no issues. If he’s doing highway speeds (lets say 55 for sake of argument) in IL with a stuck open thermostat and fan running constantly with their current IL temps, I would find it hard to believe he could get that engine cold enough to even be a problem. But, this is all based on my own experiences with these trucks. I ran my truck with no time delay at all in PA cold weather all winter long and never got it close to a cold engine. I think he will be just fine.
    1989 M998

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