iv got 2 936A2s, 1 donor, 1 running. The ovr temp was bc it was low of coolant after i did a drain and flush. I thought i had it svced but evidently after driving it a few time around the block, i noticed it very warm. It took 2 additional attempts to get it topped off.
Ill ck that thread out, but it seems, from the initial info with the query, he had the opposite issue, fan not engaging/engaged.
but again, ill ck it out in a couple wks when i get off work.
I’ll explain in depth.
When a shutterstat fails, it can fail in (2) different ways:
Scenario A: Truck runs good, may stay cool at highway speeds, but when idling or running low speeds heats up, and begins overheating rapidly, fan DOES NOT COME ON.
Cause:
1) failure of the wax temp probe failing internally (not serviceable!)
2)failure due to water and corrosion in air circuit caused by bad air drier
3)failure due to long periods of sitting, causing O rings inside shutterstat to stick in place
4)failure due to no air supplied, **please check to see if wipers and air horn doesn’t work, if they do NOT then check PPV (pressure protection valve) located under the truck. Plenty of threads cover this
5) coolant levels low or thermostat STUCK. the shutterstat is at the top of the cooling system, therefor if it never gets warm because coolant doesn’t touch it, or the thermostat is stuck closed not allowing warm coolant to exit engine block and touch shutterstat wax thermal bulb
Scenario B: truck runs good, but after truck builds air pressure the fan runs 24/7 with the engine, pulling LOTS of air and robbing valuable horsepower, as well as wearing the fan clutch bearings/belts faster
Cause:
1) Shutterstat wax temp probe failure internally (NOT serviceable!)
2) shutterstat O-Ring failure, O ring may have shrunken allowing air to bypass where it SHOULD NOT.
3) shutterstat held open from trash or debris getting in, holding valve open. Clean, replace O rings, test in boiling pot of water with air hooked to it then figure out where Debris came from upstream
4)shutterstat tension spring rusted/broken causing air to bypass, remove, repair, replace O rings.
The shutterstat isn’t complicated, it’s simply a wax filled thermostat that actuates a valve with O rings to allow air in when the truck is “too hot” and stop air from flowing when the truck is “not too hot”
Standard, Normal operation is as noted:
Truck is started up, temperature is BELOW 195ish degrees and air pressure is LESS THAN 60psi, horn doesn’t work, wipers doesn’t work; after truck builds up MORE THAN 60-90 psi (depending on what your Pressure Protection Valve is set at under the truck, restricting air to Non-essential accessories to save pressure to stop with essential brakes), you’ll notice your wipers may twitch, and then they and the horn become functional. Fan should NOT have came on at any point here.
Then you’re either idling, or driving, working the truck or not working the truck, whenever it somehow reaches 195-210°F (different shutterstats between “A0”, A1, A2 trucks activate at different temperatures) the wax bulb will actuate a Pin against spring pressure, allowing air to finally flow through and reach the fan clutch, therefor locking it in and allowing additional engine cooling capacity to prevent overheating.
A wholesome guide Written By Elijah95 on basic shutterstat operation and diagnostics
Please note the capitalized words are not yelling, it’s to break up the large paragraphs and emphasize.
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