Help me add a manual fan override switch to my 5ton

[Swamp Donkey]

I think I have a bag of 1/4" check valves already. I'll check when I get home.

I personally want to add this extra circuit for when driving at a crawl through the soft fields or woods. I'm always dragging trees or various other things to the house. Lack of air flow across the radiator, along with additional transmission heat from the added load and effort, cause the fan to cycle very frequently. I'd rather it just stay on the whole time and save wear and tear on the fan components. I'm fine with it working normally anywhere else.

How about pressurizing the VENT port of the shutter-stat with air when you want the fan to be forced ON,using an axle engagement switch. In the OFF (auto) position, the shutter-stat switch vents through the axle engagement switch, and cycles the fan as needed.

I would not try to make the shutterstat work backwards through the vent. There is an order of things that must take place internally for it to work properly. If you try to make it work out of order then it won't come on and damage is possible. Air is only meant to enter one way.

 

[74M35A2]

It should be ok. The outlet side of the shutter-stat initially has full pressure on it when the shutter-stat closes anyway, which then bleeds off through the small bleed port. Let it rip, it should work perfectly. You're not going to make history by not doing anything.

 

[RobertoGatos]

Finished the install. Very clean and works great. Took a video for you guys I'll upload later today.

 

[buggyman]

I’ve wanted to do this mod for a couple of years; but as things go I haven’t got it done.
I also like the idea of using a front axle engagement switch to accomplish this.
The reason I want to engage the fan is to use it as a cheep power retarder when going down hills.

I’m willing to buy the parts from you if you can provide a drawing/description for the proper hookup.
Thanks, Paul

This is really easy to do, and would look most at home using a front axle engagement switch. The shutter-stat has a very small air bleed hole in it so it can relieve air pressure when off to release the fan. But, I like stuff automated and to work like it is supposed to. I want to ask why you want the fan to come on earlier than 200F, but I do things nobody agrees with either. I was going to do this same mod when adding A/C, but still have it automated via a 24v air control solenoid tied into the A/C clutch actuation signal. Instead, I bought a cab roof unit with the condenser and 24v fan built into it, because I want to add the full size front mount charge air cooler.

Today's OTR trucks are now actually the opposite of how they were a short while ago. Today, big rigs fans are run as "fail-safe", meaning their air actuated fan clutch is in the locked/engaged position with no air pressure, and they require air pressure to disengage. So, loss of air in fan cooling circuit = fan on. They will rotate with the engine at first start if the vehicle has no air pressure.

So, use a front axle engagement switch/valve on your dash, with an air check valve in line with the hose which routes to a "T" you install after the shutter-stat and before the fan clutch. This is so the normal 200F engagement of air through the shutter-stat does not bleed off through the new front axle engagement switch you added, since I believe that added mechanical switch/valve has an air dump drain on the output line when in the off position (the hiss you hear when disengaging the front axle). When you pipe air into the newly added "T", you will have a small amount of air bleed going through the shutter-stat bleed hole due to it's designed in function. That hole has to be there in order to release the clutch when either switch has activated it, otherwise pressure would stay on the clutch and it would not disengage.

I can put together a care pack of what you would need with a bar napkin drawing if you want, and send it your way. Probably only a few dollars in parts. I could even fund it for the delay in shipping starters which FINALLY went out. Your tracking number will show progress by the end of the day Monday, it takes Fed-Ex almost a day to update.

 

[RobertoGatos]

The problem with pressurizing the shutterstat vent is that it's not threaded. Good idea though.

 

[WillWagner]

I forgot about the relief...I know you said you don't want to add electrics, but a horton/kysor air/electric system is a very easy and reliable set up and it can be set up as a failsafe so if there is an electrical failure, the fan engages.

 

[RobertoGatos]

Video as promised. I installed it with the parts, and as outlined in post #12 . Only thing I did differently than in the drawing was reversing the A and EA ports. I drew them backwards. Can make another napkin sketch if anyone is unclear on that, but the video is correct. Decided to not use the 6wd lever. Its a more tidy package, and mounting is easier with the other valve.

Pretty happy with how this turned out. I've had such bad luck with shutterstats, I'm glad to have a manual back up that does not involve the lockout bolts.

If someone wants to imbed this video that would be cool, here is the link. I'm not sure how.

https://youtu.be/5bkBC7KDYCc

 

[Csm Davis]

Robert you need to do a write up on your dash.