Does anyone know how to disable the stock clutch fan M998?

[Pisquinii]

Does anyone know how to disable the stock clutch fan M998? 6.2 - 3spd

I installed a electric fan and would love to disable my clutch fan. Is there an easy way to wire in a switch? Can I maybe unplug the kickdown bypass switch on the 3 spd tranny or switch it somehow there?

Any help would be great!

Thank you in advance for your help!

 

[porkysplace]

Does anyone know how to disable the stock clutch fan M998? 6.2 - 3spd

I installed a electric fan and would love to disable my clutch fan. Is there an easy way to wire in a switch? Can I maybe unplug the kickdown bypass switch on the 3 spd tranny or switch it somehow there?

Any help would be great!

Thank you in advance for your help!

View attachment 774706

It runs off a cadilac valve tied into the power steering pump .

 

[Pisquinii]

Yeah, TY, I know that, was hoping for a way to switch that out so I have it as a backup? It seems that the cadilac valve has to have a positive power to it to keep the fan not engaged.....

 

[patracy]

It seems that the cadilac valve has to have a positive power to it to keep the fan not engaged.....

Right. You probably could simply wire up a switch to provide power to the valve all the time. I would have to study the schematic to make sure it wouldn't be destructive to the TDR though. (Probably not, but I would need to check)

 

[Coug]

if you're keeping it purely as backup, unless something isn't working right it shouldn't be engaging unless the engine is getting too warm anyway, so doesn't leaving it as is meet what you are trying to do? As I understand it the system fails in an "engaged" position, so disabling it will do the opposite of what you are trying to accomplish.

If you want it to not spin at all then you'll probably have to swap out the whole system for a mechanical type clutch instead of the hydraulic one.

 

[patracy]

Good point. What is the goal, no spinning at all or just not engaging? A electric fan with a cut on of say 185F should get the engine temps below the mech fan would kick in.

 

[sandcobra164]

Stock system engages the fan clutch around 220 degrees. I agree with the two previous posters in making sure the stock system functions as designed and add your electric fan as the primary to keep engine temps a little lower.

 

[papakb]

Why not use the 24v signal from the time delay module to the kysor-cadillac valve to turn your new fan on and off?

 

[Pisquinii]

patracy, That would be awesome if you could tell me which wires to add switch too. Thank you!

 

[Pisquinii]

papakb., That would be an awesome idea...except the fan is 12 volts. It does have it's own thermostat and works well. Also if I used that power source I would still have the problem of the clutch fan being engaged all the time....

 

[Pisquinii]

Good point. What is the goal, no spinning at all or just not engaging? A electric fan with a cut on of say 185F should get the engine temps below the mech fan would kick in.

I do have it set just under the kick in temp and it is still kicking in at different temps sometimes but not as much. I wanted to turn it off with a switch to see if the flex fan can cover it alone. It seems to work great by itself. I just don't want to damage anything and want to keep it as a safety with a switch. I was reading that there is a transmission kick down cut off for the fan, and was thinking if I switched power to that, it might not hurt anything else...anyone know if this s an option? Thanks again for all the responses!

 

[Retiredwarhorses]

The electric fans are just a bad idea, sorry...
those fans will never move the CFM that the fan blade will move...IIRC, the stock blade is somewhere about 10k CFM.
If you want to use them as an additional cooling, that’s fine, but not primary.
The OEM solution works just fine...

 

[Milcommoguy]

I was scratching my head on this disabled fan thing too?? I have never had cooling issues here in the Mojave Desert where in is 115 degrees easy. When moving, air is directed and pulled thru radiators "fan box / venturi action". When needed or stopped the fan kicks in drawing huge air thru system. IMO, Don't see how a couple fan in the way of this process is an advantage. Lots of fins to deal with, restrictions.

Now if overheating is the issue, something else is going on IMO. Lots of these rigs having been sitting with crud between radiators or in (air conditioning), heater cores clogged, thermostats, pump, wrong fan?, etc,

Running cool, windows down, CAMO

 

[papakb]

When I first got my truck the fan didn't work and I looked into an electric fan. Flex-a-lite makes 24 volt fans and some nice variable speed controllers so you can leave the fan powered up all the time and then it will ramp the speed up and down as needed. Seemed like a good solution but the guys at FLEX-a-lite told me that the electric fan might not move enough air if I lived in warn climates. They were fairly expensive too so I went the 3 position switch route initially. What I had was AUTO-ON-OFF. After I figured out how the cooling system operation I fixed it I left it all in place. The time delay module is a high failure item followed by the Kysor-Cadillac valve and then I would say sticking fan clutches come in third place.

The hardest thing about the cooling system is it works backwards from what you'd expect. When the engine is cool the valve is energized allowing the fan to freewheel. It may look like it's running and I wouldn't suggest trying to stop it to test things but it should be freewheeling unless the clutch is siezed. With the engine OFF if you pressurize the line to the clutch with ~ 90psi air you should be able to rotate the fan by hand and see it moving forward and backward. When the engine hits ~230 degrees it de-energizes and that engages the fan clutch and spins the fan to cool things down. This is a failure mode system so that if the TDM or valve fail the fan is always engages providing cooling. A visual check is the fan itself moving forward and backward about 1/4" when the valve operates. With the engine running disconnecting the 2 pin connector to the valve should cause it to move. This whole thing is powered by the power steering pump providing hydraulic pressure so it needs to be topped off too.