My fan

[DCIV]

My fan, runs from the time I start it, till it stops. I never hear it "kick on" as I've read. I know it's controlled by the Cadillac valve but what I don't know is if it's running all the time it seems people say their temps stay around 180-200. Mine seems to be more like 200-220 and stays at 220. Now I know the gauges arnt the most reliable so how do
I figure out if everything is normal?

 

[DatGuyC]

Well the fan shouldn't be running from when its first powered on, so I would probably start there.

 

[simp5782]

Infrared temp gun is your best friend.

from G503:
There are 2 temperature sensors in the HMMWV. One is on the left side of the block behind the alternator. This one drives the temp gauge.

The other one is in the water crossover manifold on the top of the engine. This one controls the fan solenoid.

This crossover switch turns the fan on when the temp hits 220 degrees. This is done by REMOVING the power to the fan solenoid. Basically the same as unplugging the solenoid connector. This causes the fan to engage. It will run until the engine temp gets down to about 180-190 degreees when it reapplies power to the fan solenoid, disengaging the clutch and allowing the fan to spin freely.

The easiest way to determine if this is working is by listening to the system with the engine running. With the engine warmed up to operating temperature (190-220) you should hear a difference in the sound of the fan with the connector plugged in and unplugged. You should visually see the fan move forward and backwards about 1/4" as the fan clutch operates. DON'T try to stop the fan with anything, you'll probably just end up breaking fan blades off.

If you are still running at 220 degrees with the fan running then you may have a blocked or partially opening thermostat or a defective gauge. You can try removing the thermostat and seeing what happens. To check the gauge remove the temp sender and drop it into a pan of near boiling water and see if it reads ~210 degrees. You will have to add a clip lead to ground the sender when you do this.

There is one other element that gives us headaches and that's the time delay module. It's function is the remove drive to the fan when fording. Flooring the accelerator momentarily will actuate the solenoid for 20 seconds to allow you to enter the water with drive removed from the fan to keep it from snapping blades off when the water reaches that level in the engine compartment. The best way to check it is to replace it.

 

[DCIV]

I read that exact post off another forum. I still dont know where to start if the fan is running from the get go. Does that mean my temp sensor on the the water crossover is bad? Is there only one speed for the fan? On/off? Just odd that if its running all the time the temp doesnt go above or below 220. I would love it to be pegged out and know its the thermostat. Just odd and dont know where to start.

 

[charlietango]

I read that exact post off another forum. I still dont know where to start if the fan is running from the get go. Does that mean my temp sensor on the the water crossover is bad? Is there only one speed for the fan? On/off? Just odd that if its running all the time the temp doesnt go above or below 220. I would love it to be pegged out and know its the thermostat. Just odd and dont know where to start.

You’re sure it’s running and not just spinning? Mine spins but isn’t under load. Sounds like afterburners when it kicks in. I thought I read somewhere that if the valve was bypassed or bad it would remain ‘on’ all the time but I’ll search for that. Was one of those random read the forums at 0400 can’t sleep memories so don’t hold me to it

 

[DCIV]

You’re sure it’s running and not just spinning? Mine spins but isn’t under load. Sounds like afterburners when it kicks in. I thought I read somewhere that if the valve was bypassed it would remain ‘on’ all the time but I’ll search for that. Was one of those random read the forums at 0400 can’t sleep memories so don’t hold me to it

I know if I unplug the cadillac valve it turns it on....maybe its not running and is just spinning. I will go try.

 

[charlietango]

I know if I unplug the cadillac valve it turns it on....maybe its not running and is just spinning. I will go try.

Can the HMMWV cadillac valve be repaired?

https://r.tapatalk.com/shareLink?sh...iers.com/showthread.php?t=164498&share_type=t

This is where I read that if the valve goes bad it defaults to ‘on’

But yeah mine spins under engine idle but I can stop it - if you trust sticking something in there that is. It’s VERY loud when it runs. Do NOT trust the thermostat gauge....

 

[simp5782]

If its not roaring then its off. You know what it sounds like when your going 55 and it comes on. Some people think an airplane is landing on top of them. It should spin as It has bearings and some should play into resistance with the pulley.

 

[DCIV]

Well unplugged the valve and it kicked on, so it's just spinning but not engadging. I don't know if I should feel better or not yet.

So first should I start with the temp sensor to make sure it's sending the signal to the valve?

 

[simp5782]

Well unplugged the valve and it kicked on, so it's just spinning but not engadging. I don't know if I should feel better or not yet.

So first should I start with the temp sensor to make sure it's sending the signal to the valve?

Check it with a volt meter or test light. Ohm the sensor out and see what its resistance is. If its a wacky number you know its off. You should ohm it cold start and at running temp.

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[DCIV]

Also, with everything off, should I be able to turn the blade by hand?

 

[DCIV]

I am going to get my volt meter out but I am going to go out on a limb and say someone has already been down this road before me.

I am also going to try and clean my valve but if I can't, where it the best place to pick one up?

 

[simp5782]

Most surplus places have them. or ebay. You can try posting in the parts wanted section. Yes you should be able to turn the fan. It should be able to move with the bearing resistance it rides on. When the fluid is added to the clutch it locks it up to make it move at the engine speed of the pulley its being driven by the belts. It is basically the same principle as a stutterstat for air clutches on the bigger trucks. its just fluid rather than air.

 

[DCIV]

Most surplus places have them. or ebay. You can try posting in the parts wanted section. Yes you should be able to turn the fan. It should be able to move with the bearing resistance it rides on. When the fluid is added to the clutch it locks it up to make it move at the engine speed of the pulley its being driven by the belts. It is basically the same principle as a stutterstat for air clutches on the bigger trucks. its just fluid rather than air.

That makes a lot of sense....I can not move mine, not even a little. This is getting worse and worse haha.

 

[kzeyus]

Think you may be getting this backward. When the fan gets hydraulic pressure, it disengages. That way the fan defaults to on if pressure fails for some reason. So with everything off, the fan should be engaged and difficult to turn. If you unplug the TDM while running and fan engages, then Cadillac and fan clutch would seem to be working. The fan is disengaged (has pressure) until TDM is unplugged (loses pressure) which engages it. Only two questions remaining are if tdm works and if fan is engaging (hydraulic pressure removed) at the right temp. So check temp at which it comes on - ours is around 220 and you can feel and hear when it engages. Then once you know fan is engaged and running and on the road, press accelerator to floor (as if passing) and see if it disengages for 30 seconds or so - if so TDM is working. TDM shuts off a running fan for 30 seconds or so for passing (as if we pass anyone) or for deep water fording.

 

[DCIV]

Okay so the fan should not turn when the vehicle is off then. I am positive that the fan has never "engaged" like it did when I unplugged the cadillac valve. I contacted a person on the forum who sells them for cheaper than on line.

 

[Bulldogger]

Okay so the fan should not turn when the vehicle is off then. I am positive that the fan has never "engaged" like it did when I unplugged the cadillac valve. I contacted a person on the forum who sells them for cheaper than on line.

My 1987 6.2L maintains the temps at 220F. Yours sounds like mine. Not sure it's got a problem.

Bulldogger

 

[kzeyus]

I may be off here so check with the pros, but I would think if unplugging TDM engages fan, your Cadillac valve is probably good, I'd be more suspicious of the temp sensor or something between sensor and valve. TDM could also be bad and forcing fan to disengage all the time, but it's cheaper to try than the Cadillac valve. When our TDM went bad, fan worked normally except flooring accelerator would not temporarily disengage fan.

 

[charlietango]

I just went outside- vehicle off fan will not spin. kzeyus is correct here. I don’t think you have any problems to worry about. Time for a beer!


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[DCIV]

More info (maybe weirdness) Cadillac valve plugged in, deff a hissing sound, unplugged hissing goes away. Also unplugged it will not cool down from 200. Just idling in the driveway, hood up, valve unplugged....nothing lower than 200. Also I can put my hand on the radiator, it's warm....but not enough for me to want to remove it. Almost leaning towards thermostat now. Shouldn't the fan make it go below 200...unless the water wasn't circulating?