Fan Solenoid replacement

Ajax MD said:

...except that we don't use power steering fluid, we use Dexron/Mercon ATF.

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Yes, of course ATF, sorry for that. I was thinking "fluid" vs. "pressurized air", but it´s better to be precise.

AAVP7 said:

Yes, of course ATF, sorry for that. I was thinking "fluid" vs. "pressurized air", but it´s better to be precise.

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Are we saying that we don't use power steering fluid in the power steering reservoir, but use ATF fluid....or is power steering fluid the same as ATF?

That what HE said. To add not the same.


AND THAT'S A LUBE ORDER...Pvt, CAMO

Okie Dokie......

Thumper580 said:

Are we saying that we don't use power steering fluid in the power steering reservoir, but use ATF fluid....or is power steering fluid the same as ATF?

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Correct. As crazy as it sounds, add Dex/Merc automatic transmission fluid to the reservoir. As Milcommo says, it's all in the Lube Order.

Ajax MD said:

Correct. As crazy as it sounds, add Dex/Merc automatic transmission fluid to the reservoir. As Milcommo says, it's all in the Lube Order.

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I'll drain out as much as I can when I put the new fan clutch on the truck.... since I've replaced every other related part. Hopefully, it's not so stuck I can't get the bolt holes to line up... That would suck after taking the three cooling stacks off.

Thumper580 said:

I'll drain out as much as I can when I put the new fan clutch on the truck.... since I've replaced every other related part. Hopefully, it's not so stuck I can't get the bolt holes to line up... That would suck after taking the three cooling stacks off.

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Did you add P/S fluid, or did a previous owner do it? Or are you just doing a general flush of the system?

Ajax MD said:

Did you add P/S fluid, or did a previous owner do it? Or are you just doing a general flush of the system?

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I can't swear what was in there before but I have added some power steering fluid to it. Whatever I can gravity drain out I'll replace with ATF.

Both are approximately a 10w viscosity with different additive packages. Power stg fluid has anti foam additives and ATF has additives suitable for internal transmission clutches, valves, etc.

A little mixing of both won't be the end of the world.

Different topic, but 5 ton's routinely have 10w , 15w40, or atf in the allsion transmissions and virtually impossible to remove every drop when making a conversion. Those get mixed and become gumbo
Hotly debated which is best but those theories don't apply to hmmwv fan clutch, power steering and hydraulic winch is so equipped.

Drain if you want but don't panic.

Milcommoguy said:

Well, I tried from here. It has and can work. Here's some encouragement.

View attachment 814062

Good luck. Oil and beer, CAMO

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Ok so I have changed the Cadillac valve, time delay and fan drive switch also new thermostat and hoses and coolant. I did the air test on the fan shroud and the fan disengages and free spins. When I drive it never gets above 190 degrees I can’t tell if the fan is always on or not. I have driven it 26 miles on the highway@60mph and it won’t budge off 190 degrees I used my laser temp and the motor is like 185-199. The temp here is like 55degress while I’m driving. I’m not sure if it’s normal at this point.


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Dpas1973 said:

Ok so I have changed the Cadillac valve, time delay and fan drive switch also new thermostat and hoses and coolant. I did the air test on the fan shroud and the fan disengages and free spins. When I drive it never gets above 190 degrees I can’t tell if the fan is always on or not. I have driven it 26 miles on the highway@60mph and it won’t budge off 190 degrees I used my laser temp and the motor is like 185-199. The temp here is like 55degress while I’m driving. I’m not sure if it’s normal at this point.


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Click to expand...

Well you might have a REAL COOL Humv?

I not a fan of just changing stuff, just to be changing stuff. Were any tests made to really see whats going on. Maybe yours is OK and mine is wacky below.

Mine runs 190 to 220 +/- a couple degrees. Always in some state of swinging between the high and the low temps while holding for a minute at the high or low ends. Never a steady state in my rig.

With 117 desert degrees outside or hard engine loads... gets up to the 220 side in few minutes, hangs there a moment, Fan kicks in with a roar. In less than 30 seconds temp is slowly on the way down to 190. Fan turn off...holds there for a minute and slowly rising. Rarely see temps over 220 and if so the fan pulls it right into range. Fan is always cycling. There is a lot hysteresis in the system due to retention of heat in the block, switch action, air and water flow.

Don't see temps below 190 +/- either... unless it warming up, OR is cold as "freeze your buns OFF!" And forgot the cardboard radiator blocker. LOL

Now in cooler weather like we are heading into or even winter temps of 35, the cycling is extended to greater times. Time being miles (more or less) I can run for 5 or 6 miles before cycle times.

As stated I don't see a steady state for very long at the high or the low numbers. Mine is like a real s l o w heartbeat.

Another CAMO mod is I have a dash indicator (simple inverter circuit & LED) connected on my Cadillac valve solenoid showing fan action. Most of the time the fan run times are very short. About a minute at speed.

Light and blast of hot air. It's alive, CAMO

My results. YRMV. No animals were hurt in these observations. Maybe a few bugs.

Milcommoguy said:

Well you might have a REAL COOL Humv?

I not a fan of just changing stuff, just to be changing stuff. Were any tests made to really see whats going on. Maybe yours is OK and mine is wacky below.

Mine runs 190 to 220 +/- a couple degrees. Always in some state of swinging between the high and the low temps while holding for a minute at the high or low ends. Never a steady state in my rig.

With 117 desert degrees outside or hard engine loads... gets up to the 220 side in few minutes, hangs there a moment, Fan kicks in with a roar. In less than 30 seconds temp is slowly on the way down to 190. Fan turn off...holds there for a minute and slowly rising. Rarely see temps over 220 and if so the fan pulls it right into range. Fan is always cycling. There is a lot hysteresis in the system due to retention of heat in the block, switch action, air and water flow.

Don't see temps below 190 +/- either... unless it warming up, OR is cold as "freeze your buns OFF!" And forgot the cardboard radiator blocker. LOL

Now in cooler weather like we are heading into or even winter temps of 35, the cycling is extended to greater times. Time being miles (more or less) I can run for 5 or 6 miles before cycle times.

As stated I don't see a steady state for very long at the high or the low numbers. Mine is like a real s l o w heartbeat.

Another CAMO mod is I have a dash indicator (simple inverter circuit & LED) connected on my Cadillac valve solenoid showing fan action. Most of the time the fan run times are very short. About a minute at speed.

Light and blast of hot air. It's alive, CAMO

My results. YRMV. No animals were hurt in these observations. Maybe a few bugs.

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I’m just at a loss lol. I appreciate all the help you guys have given me but now what lol. Everything is new and the fan clutch disengages with the compressor hooked up. It must be engaged at all times because why would my temp never get over 190 even on the 70+ degree days driving 26 miles to work?


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Dpas1973 said:

I’m just at a loss lol. I appreciate all the help you guys have given me but now what lol. Everything is new and the fan clutch disengages with the compressor hooked up. It must be engaged at all times because why would my temp never get over 190 even on the 70+ degree days driving 26 miles to work?


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I'm looking at the different parts websites, the 998A0/A1 6.2/6.5 detuned thermostat is rated at 190 (fully open) and the A2 trucks are 190F or 195F, so the fact that your truck is getting up to those temps leads me to believe the thermostat is functioning properly.

The first few hundred miles I drove my truck the fan almost never kicked on. As long as I wasn't doing above 50mph, but still moving above 25mph, there was enough airflow to keep everything cool where it's supposed to be (though I confess mostly I didn't pay attention to the temp gauge, so can't tell you what it was at)
When driving the truck for long periods of time at parade speeds (crawling at like 2mph) the fan would eventually kick in and I'd know it.

Now with my truck having a big box on the back and weighing over 9k lbs, the fan does tend to cycle when I'm driving around, especially with the A/C on.

The fact is 190F is operating temperature for this truck (low end, but still in the range) so without doing something to load down the engine to force it to make additional heat I wouldn't be too worried about it.


To back up a step, you never actually mention what engine and transmission your truck has. I see mention of a serpentine belt, but that's it.
If yours is a 4 speed truck and you've been driving it at 55mph or less, then that 190F is believable, as it runs at lower rpms than the 3 speed.



So one more test you can do to check the fan system function, set the throttle up at a decent speed (like 1500 rpms), and unplug the cadillac valve. If the clutch is disengaging properly like it's supposed to, when you unplug the cadillac valve you should definitely hear the fan speed up.

Coug said:

I'm looking at the different parts websites, the 998A0/A1 6.2/6.5 detuned thermostat is rated at 190 (fully open) and the A2 trucks are 190F or 195F, so the fact that your truck is getting up to those temps leads me to believe the thermostat is functioning properly.

The first few hundred miles I drove my truck the fan almost never kicked on. As long as I wasn't doing above 50mph, but still moving above 25mph, there was enough airflow to keep everything cool where it's supposed to be (though I confess mostly I didn't pay attention to the temp gauge, so can't tell you what it was at)
When driving the truck for long periods of time at parade speeds (crawling at like 2mph) the fan would eventually kick in and I'd know it.

Now with my truck having a big box on the back and weighing over 9k lbs, the fan does tend to cycle when I'm driving around, especially with the A/C on.

The fact is 190F is operating temperature for this truck (low end, but still in the range) so without doing something to load down the engine to force it to make additional heat I wouldn't be too worried about it.


To back up a step, you never actually mention what engine and transmission your truck has. I see mention of a serpentine belt, but that's it.
If yours is a 4 speed truck and you've been driving it at 55mph or less, then that 190F is believable, as it runs at lower rpms than the 3 speed.



So one more test you can do to check the fan system function, set the throttle up at a decent speed (like 1500 rpms), and unplug the cadillac valve. If the clutch is disengaging properly like it's supposed to, when you unplug the cadillac valve you should definitely hear the fan speed up.

Click to expand...

I have a 6.5 4 speed and I do 60+ on the highway to work and it won’t budge past 190 degrees. The temps haven’t been over 75degrees but still I have done the 26 miles each way 4 times to work and it didn’t move past 190 with the old TSTAT and valve and time delay and it hasn’t with the 350 I spent on parts I probably didn’t need.


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Dpas1973 said:

I have a 6.5 4 speed and I do 60+ on the highway to work and it won’t budge past 190 degrees. The temps haven’t been over 75degrees but still I have done the 26 miles each way 4 times to work and it didn’t move past 190 with the old TSTAT and valve and time delay and it hasn’t with the 350 I spent on parts I probably didn’t need.


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Click to expand...

so last thing to do is verify if the fan is disengaging properly. With the RPMs up a bit (like 1500ish) it should be very noticable if the fan kicks in or if it was already on when unplugging the cadillac valve or time delay module (as system defaults to "engaged")

Coug said:

so last thing to do is verify if the fan is disengaging properly. With the RPMs up a bit (like 1500ish) it should be very noticable if the fan kicks in or if it was already on when unplugging the cadillac valve or time delay module (as system defaults to "engaged")

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Ok I have unplugged the valve at idle and no change I’ll have to try with throttle locked at higher rpm.


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Think we have been over this a few times...

With all the new parts and they are OEM ??? right. (no funky thinking this or that might work) You might be OK and just not hearing the fan kick in. If the temps are running it the 200 range might just be a very good clean block and radiator. To be sure...

Time to get out the prints and follow along with a mulitmeter.

Are you sure of the pressure lines connections to the valve?

Have you connected the water cross over thermo switch leads together? This will disengage fan allowing engine to run up in temperature. Assuming all the new stuff is working correctly. Connect the two together and run it out watching the gauge temp... and is that thing working correct?

Not going to guess here without some clear data points. But I bet something funky with the electrics as in themo switch, no power to the valve.

Old girl running hot and cold, CAMO

Milcommoguy said:

Think we have been over this a few times...

With all the new parts and they are OEM ??? right. (no funky thinking this or that might work) You might be OK and just not hearing the fan kick in. If the temps are running it the 200 range might just be a very good clean block and radiator. To be sure...

Time to get out the prints and follow along with a mulitmeter.

Are you sure of the pressure lines connections to the valve?

Have you connected the water cross over thermo switch leads together? This will disengage fan allowing engine to run up in temperature. Assuming all the new stuff is working correctly. Connect the two together and run it out watching the gauge temp... and is that thing working correct?

Not going to guess here without some clear data points. But I bet something funky with the electrics as in themo switch, no power to the valve.

Old girl running hot and cold, CAMO

Click to expand...

I’m going to do that tomm when I’m home put the 2 leads together I mean this is the 2nd fan drive switch one is the blue label also. When I start the truck the hose that goes to the power steering cooler from the Cadillac valve gets rock hard when I disconnect the Cadillac valve hose goes limp so I’m assuming the valve is working fine. The only thing I didn’t do is jumping the fan drive switch out like you said.


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Milcommoguy said:

Think we have been over this a few times...

With all the new parts and they are OEM ??? right. (no funky thinking this or that might work) You might be OK and just not hearing the fan kick in. If the temps are running it the 200 range might just be a very good clean block and radiator. To be sure...

Time to get out the prints and follow along with a mulitmeter.

Are you sure of the pressure lines connections to the valve?

Have you connected the water cross over thermo switch leads together? This will disengage fan allowing engine to run up in temperature. Assuming all the new stuff is working correctly. Connect the two together and run it out watching the gauge temp... and is that thing working correct?

Not going to guess here without some clear data points. But I bet something funky with the electrics as in themo switch, no power to the valve.

Old girl running hot and cold, CAMO

Click to expand...

So I ran outside of work and if I disconnect the brand new fan drive switch the Cadillac valve goes silent when I connect the fan drive switch the Cadillac valve starts hissing and the lines get rock hard


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Dpas1973 said:

I’m going to do that tomm when I’m home put the 2 leads together I mean this is the 2nd fan drive switch one is the blue label also. When I start the truck the hose that goes to the power steering cooler from the Cadillac valve gets rock hard when I disconnect the Cadillac valve hose goes limp so I’m assuming the valve is working fine. The only thing I didn’t do is jumping the fan drive switch out like you said.


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Click to expand...

Well now the line pressurizes, pumps up and in doing so... SHOULD SEE the fan free wheel, or pull the plug and fan locks up.

Something is dicked up or you not seeing it, feeling it... cuz that's one of the quickie test. LOL

For fan to cycle, thermo switch is the part doing the business. It opens the circuit at +/- 225 and on comes the fan. if one as voltage at the switch? With a cold engine or connected together, making it to the TDM and out to the valve. Loss of voltage or a break in any wire... FAN will NOT run free. For whatever the reason this process confuses the poop out of many.

Watch out for those "packard connectors" maybe or could be an open circuit in one. This is why the test light (cheap) or mulimeter is going to be your best-est buddy to follow the circuit. When you have a correct working system to play on , the pull this or pull that connector will make science sense.

Pull my finger and turn on the fan, CAMO

And now a couple of utube videos> Watch and learn. This is what you NEED to know in the driveway or on the trail.


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