Actuator, Air Fan Clutch for M923a1

bigwhale · Dec 23, 2014

I tried taking mine apart as well maybe 3 times, but this valve is very troublesome. A much easier and cheaper fix is mentioned in my previous threads. If your concerned about keeping the truck orginal, then just take the valve out and store it somewhere. Mine did the same thing, leaking and it kept the fan "on " all time which is not good for the clutch and it robs horsepower from the truck. There are "dealers" that sell the valve but your going to pay around 200 bux for it which is ridiculous. I fixed mine for less than 10 bux. Since I do not use the ether valve and have a plug in block heater I used that circuit to power the solenoid valve to operate the fan, I just watch the temp gauge and push the button and hold it for a minute or two to engage the fan, but my truck runs cool anyway and never had to press it more than once. I plan on removing the old valve and putting a thermoprobe in the hole to make it automatic later. Its so easy a caveman can do it !!

idbankrman · Jan 28, 2015

Strouty I have the same problem with another truck I have and it appears to me that the large O ring is the problem. I'm pretty sure it is an O ring it just tends to get deformed and flattened. I tried a loose fitting large O ring and got the problem you are having. (Fan on, actuator venting air out cap) I am going to try a tighter O ring as I think this is what I did on the first truck. I'm not sure how tight to make the nut.

todds112 · Jan 28, 2015

http://www.steelsoldiers.com/showthread.php?133552-Major-air-leak-at-Fan-shutter-stat&highlight=

This was a thread I started and the O-Ring I found that will work.

tbar123 · Feb 8, 2015

I'm currently working on this myself. A couple questions. I took the air lines to and from off the actuator and started the truck. I then took my air hose and blew some air into the fan clutch and it worked. Thank God! All kinds of dust and debris blew out from the radiator, SO I know it hasn't worked for some time. But I noticed there wasn't any air coming from the compressor. Shouldn't there be constant air coming in? If not what triggers the air to turn on? Thanks for any help.

M35A2-AZ · Feb 8, 2015

tbar123 said:
I'm currently working on this myself. A couple questions. I took the air lines to and from off the actuator and started the truck. I then took my air hose and blew some air into the fan clutch and it worked. Thank God! All kinds of dust and debris blew out from the radiator, SO I know it hasn't worked for some time. But I noticed there wasn't any air coming from the compressor. Shouldn't there be constant air coming in? If not what triggers the air to turn on? Thanks for any help.

Yes there should be air to the fan actuator all the time.

tbar123 · Feb 8, 2015

Thanks M35;Any ideas on what would stop airflow to the actuator?

M35A2-AZ · Feb 8, 2015

I would check the hose and then just start working backwards.
Due to you dirt come out the other side I would guess it maybe some type of dirt& sand.

grendel · Feb 28, 2015

Working on this now.. it turns on my fan, senses temp and all that, but leaks air out, discharging my secondary air tanks when it's shut off.

tbar123 · Mar 1, 2015

Is it leaking air from the actuator? If so just remove the inserts ( while on the engine ),clean the threads, add new teflon tape and reinstall. If not get the truck to full air ,shut the truck off and listen for the air leak. Then report back, so that someone can help with better advice on the exact leak you have.

Carlo · May 28, 2015

70deuce said:
Here is the one that wasn't working out of my M936A2. If you are talking the bulb (probe) it ends approx 1&1/2 inches from the base of the main unit. This is an Evans unit.

I know this post is old but do you know if adjusting it out makes it trip at a lower temp?
thanks

Strouty · May 28, 2015

I am curious as well.

Carlo · May 28, 2015

wheelspinner said:
I really needed these pictures today. I had my truck (923A2) hooked up to tow my deuce to NC. Figured I better get a shakedown out of the way so I took the combo about 5 miles for a fuel-up. Coming back up the hill, started getting hot, up to about 220, with no sign of the fan......

I figured the shutter-stat was most likely the culprit and took it all apart, and found no real problem. Hmmmmm.

I did notice that the probe was not tightened all the way in (I mistakenly thought it should be ! ) and tightened it all the way in and tightened the locknut. Seemed like it should be good.

When I went to put it all back together is when I found the REAL problem with mine.......the air hoses were switched in was on out, and out was on in. DOH!

Now the new problem was that by tightening in the probe all the way, it sends the unit to "fail-safe" and runs the fan continuously (This is good to know information)

So........back apart it all comes, now that I know the air hoses were wrong, and most likely the problem all along, I decided I better readjust the probe length (which is why I said I really needed these pictures ! )

After filling the cooling system yet again, and getting it hot enough, finally got the fan working as it should.

So, long story short, never assume anything and check everything. Had I noticed the switched air lines, this would have been a 30 second fix.

View attachment 516671

Should the probe be fixed all the way in? I would think this would cause it to turn on sooner but I don't know nothing at this point. I'm lost in space and afraid I will buy a new one.

Carlo · May 28, 2015

nf6x said:
I think that I have fixed my shutter stat. I replaced three of the smaller o-rings for which I had the right sizes in my o-ring kit. I didn't have quite the right size for the larger o-ring, and I left the one under the crimped retainer alone. I cleaned out the valve and lubed the o-rings with silicone grease, and then bench-tested the valve with an air compressor and hot water from the kitchen stove. It appears to work properly without leaking, so I'll put it back in the truck. If it acts up again, I'll probably just replace it at that point.

Thanks again for the photos. I have a couple of questions, mine is not leaking out the rear aluminum cap, but if I loosen the cap the fan turns on. I now see the plunger from your photos and will remove this tomorrow to see if O-rings are ok. Do you know if adjusting the temp sensor bulb does anything?
Thanks again.

idbankrman · Jun 11, 2015

The temperature at which the actuator opens to direct air to the fan clutch varies with how far the probe end is screwed into the body of the actuator. Screwing it in or tightening it causes a lower activation temperature. When taking it apart to change O rings count the turns required to get it apart and scratch a mark across the probe and barrel so you can return it to the same place. If you mess this up adjustment becomes trial and error.

Carlo · Jun 12, 2015

idbankrman said:
The temperature at which the actuator opens to direct air to the fan clutch varies with how far the probe end is screwed into the body of the actuator. Screwing it in or tightening it causes a lower activation temperature. When taking it apart to change O rings count the turns required to get it apart and scratch a mark across the probe and barrel so you can return it to the same place. If you mess this up adjustment becomes trial and error.

Thanks I will give it a try this weekend and let you know if it helped.

Marc23760 · Jul 27, 2015

idbankrman said:
The temperature at which the actuator opens to direct air to the fan clutch varies with how far the probe end is screwed into the body of the actuator. Screwing it in or tightening it causes a lower activation temperature. When taking it apart to change O rings count the turns required to get it apart and scratch a mark across the probe and barrel so you can return it to the same place. If you mess this up adjustment becomes trial and error.

This seems to be the case.

I am nexw to this site and have spent hours reading most of the posts about these fan temp actuators. I have a 1991 M923a2 with the 8.3

i have been fighting with this thing for several attempts. First cleaning it, then removing it completely and cleaning both ends. To hopefully make a long story short for the next reader, I backed out the silver end cap while it was at temp (200+) when it wouldn't engage properly and the fan came on when I had it almost all the way out. It seemed as though the probe needed adjusting, (AFTER having it out and cleaning it etc) where as I thought it was just as jammed as when I started.

if you can see the plastic pin sticking out of the center of the silver cap when it's hot (as opposed to inwards when cold) you at least know the non-repairable part of the actuator is working. However, after several attempts of adjusting the probe side (in the coolant end) I am just trying to get the stat to open the valve when it's supposed to, in the correct place to move air. After the third try I'll know in the morning when it's hot if I have the adjustment correct. But for the life of me this week I cannot seem to get it working correctly.

Bobbed 923A2 · Feb 27, 2022

Question On the 8.3 M923A2 shutter stat inlet air hose goes to the fan clutch?

Jbulach · Feb 27, 2022

Outlet goes to the clutch.

Jbulach · Feb 27, 2022

Bobbed 923A2 · Feb 27, 2022

Jbulach
The only go to resource for these steel soldiers!! That's what I thought air supply in and out to the power source in my case the fan clutch a cummins mechanic I know no no dude!! Thank god for Steel Soldiers you guys are awesome appreciate it.

I have another question is there an air hose replacement kit available for the air brakes that go to and from the manifold or do I have to have them made? replaced the front took a minute to find those and the rear nobody
Thanks again

Actuator, Air Fan Clutch for M923a1

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