Fan Clutch Solenoid issue

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wyocommo

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Spent the afternoon troubleshooting why the fan clutch does not engage at proper temp. Clutch is working as advertised when air is removed.

When power is removed from quick exhaust solenoid it does not exhaust air in the clutch circuit to allow the clutch to engage.

Dismantled solenoid and cleaned, appears to be OK.

Reinstalled but no joy. If engine is stopped and air system pressure begins to bleed off it will eventually exhaust as it should.

My conclusion is either a bad solenoid, which it sure doesn't look bad, or way too much pressure on the wet tank output air circuit.

Could not locate the specified pressure required out of the protection regulator on the wet tank.

Does anyone know what the protection regulator pressure output should be???

I did a quick disassembly on the regulator and it appeared OK.
 

Suprman

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The tm has troubleshooting step by step check this check that flow chart. Even the army techs I ask say the same for the first gen lmtv trucks. Follow the tm. I have to do it next week myself I have one that starts fine if I jump the starter relay but does nothing from the push button. The A1 trucks have good computer diagnostics plug in and run the program.
 

wyocommo

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Dont think it will matter in this situation. No power is applied to the solenoid when it engages the fan clutch. The solenoid is normally powered up to pass air to the clutch to keep it from engaging. This problem is occurring when the solenoid is powered down.

It is a block and bleed function where it blocks the supply pressure and then bleeds the output going to the clutch to cause it to engage. It is not releasing the down stream pressure going to the clutch until some of the supply side pressure reduces when the engine is stopped. It should release it immediately when the solenoid is powered down.

Pretty much must be a defective unit since it says it is rated for 140 psi. No way the wet air is that high of a pressure.
 

Suprman

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Air keeps the fan off no air th fan should come on. Reverse from the m939 trucks. Maybe it's something that can be taken apart and cleaned maybe a line has some gunk blocking it.
 

wyocommo

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OOO Kaay_ Dismantled fan clutch solenoid for the third time. This time I put a tiny bit of 30 weight motor oil on the rubber pads that seat on the cones at each end of the solenoid. Magically, the solenoid is now operating as advertised.

A good friend once told me that EVERYTHING works better with lubrication,,,,, looks like he was right again:grin:
 

Oxyacetylene

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I think mine is having a similar problem. I took the solenoid apart, and there isn't much to repair with it. I put it back together and started applying power repeatedly using a couple jumper wires. I could then start hearing a faint clicking when power was removed, but I had to have it right by my ear to hear it. Also, when I disconnected one of the air lines, air pressure released, so I'm pretty sure mine was not releasing the pressure. Now when I first crank the truck (cold), the fan turns and pulls a lot of air, until air pressure builds and the clutch disengages. I'm hopeful that it will operate correctly now, but I need to drive it around during the heat of the day to try and confirm.
 

wyocommo

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An easy test for the function of the solenoid only is to start the truck, let it run and wait for the fan to disengage when air pressure builds to normal. If you then shut the truck off, which kills power to the solenoid, you should immediately hear the solenoid vent the air that is in the line going to the clutch.

My solenoid would not disengage until some of the air pressure bled off of the supply in the wet tank.

As an FYI, my solenoid was the Berkert 0301 unit. I think other suppliers were used also but any block and bleed function unit with 24 volt coil should work.
 

Pointman0853

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My fan clutch was working fine, now it appears to be non-op.

If I'm following these threads correctly, when the truck is shut down and air has bled off, the fan should not rotate freely? If I crawl under and push on the fanwhen the truck has been sitting, the fan turns freely.

So, when first started it should move air until the system airs up and then it will 'freewheel' until the temp sensor activates the solenoid and bleeds the air off?

Naturally, I'm hoping this is an easy fix.. Ideas anyone? Thanks in advance..

Pointman
 

wyocommo

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Casper, WY
My fan clutch was working fine, now it appears to be non-op.

If I'm following these threads correctly, when the truck is shut down and air has bled off, the fan should not rotate freely? If I crawl under and push on the fanwhen the truck has been sitting, the fan turns freely.

So, when first started it should move air until the system airs up and then it will 'freewheel' until the temp sensor activates the solenoid and bleeds the air off?

Naturally, I'm hoping this is an easy fix.. Ideas anyone? Thanks in advance..

Pointman
I have not tried to rotate the fan by hand so I can't be positive on that aspect, but it would appear that should be how it works. i would start by loosening the fan clutch air line at the output of the solenoid to verify that there is no air pressure trapped in the line.

My solenoid was flaky in several aspects and the problems seemed to come and go. I completely disassembled the solenoid several times and cleaned, lubed everything but it was never able to make it reliable so I replaced it.
 

Pointman0853

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Thanks, After reading the applicable threads, I have ordered a replacement/spare. Its getting hot in Nevada and I'm taking no chances.. Will report back here when resolved.

Pointman
 

Lmtv772

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if the solenoid isn't clogged/ stopped working. you should hear a loud. 'pffft' when you turn your truck off. provided there is air in the tanks.
 

Rebuilder

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I had the same problem and it was the solenoid sticking. I could tap mine when the engine temp was above 200 and it would release the air and start the fan. Did that for the last few hundred miles of my recovery... with help from my passenger of course.
 

pinmode

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This thread saved me today so I wanted to pop in and say I also have a bad solenoid in an M1083 and can confirm that giving it a good whack when > 205 degrees releases the valve, causing the engine fan to turn on. Replacing the solenoid soon (found it on fee bay "Parker 8204 0459-45 24v-dc Solenoid Valve 0524473Z"), but I needed to drive hundreds of miles today through the SLC inclines. The tap method worked out great!

One curious thing - I have two solenoids side by side, same specs. I'm not sure what the 2nd one is or which is which.
 

Coffey1

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Mine same problem coil would heat up and no fan.
Removed crappie valve and put good quality valve in no more issues.
 

Third From Texas

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Anyone have a lead on a PARKER 8204 0459-45 24V-DC SOLENOID VALVE D445718 ?

My OEM Burkert coil functions but the rubber has finally degraded off completely on the bottom side of the plunger. Now it just dumps air each time the fan comes on (annoying, but functional) and then bleeds the wet tank completely when parked (again, more of an annoyance). I'm fixing to drive across Texas and in this heat I don't want any further surprises.

Not really looking to replace it with another Burkert new or used.

Or has anyone ever attempted to re-surface the plunger with a thin rubber coating?
 

simp5782

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You can go with a horton style thermal switch and solenoid. Cheaper i am sure than the parker. Also has a lifetime warranty. Mine has seen 300k+ plus miles
 
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