HMMWV M1123 Clutch Fan control box disconnected

[Thunderbirds]

Hey, shout out to all experienced mechanics here...

Question. My M1123 (still on it's way from the yard, not here yet) has the fan clutch control box (also known as the time delay solenoid) disconnected. I haven't had the chance to work on it you, but to save troubleshooting time, does anyone have experience why the military would have disconnected it? What can I expect when the truck gets here, is the control box inop, or do you think they did it to save on Horsepower?

I am only going off pictures from GP...



Here is a close up:



Thanks!

Lee

 

[Coug]

Time Delay Module. It's purpose is to disengage the fan if you stomp all the way down on the throttle. This is primarily for water fording situations, to disengage the fan before entering water, or the fan gets destroyed. It also frees up the power from the fan system if you really need to move (fan takes something like 10hp)

If the TDM or the fan thermoswitch fail, it can prevent the fan from engaging and cooling the engine.

Disconnecting the TDM will force the cooling fan to stay engaged. You lose a little engine power, but it keep everything cooled like it is supposed to

 

[Thunderbirds]

Time Delay Module. It's purpose is to disengage the fan if you stomp all the way down on the throttle. This is primarily for water fording situations, to disengage the fan before entering water, or the fan gets destroyed. It also frees up the power from the fan system if you really need to move (fan takes something like 10hp)

If the TDM or the fan thermoswitch fail, it can prevent the fan from engaging and cooling the engine.

Disconnecting the TDM will force the cooling fan to stay engaged. You lose a little engine power, but it keep everything cooled like it is supposed to

Awesome, thank you Coug. I knew it delays and disconnects the fan, but I must have misunderstood the theory of operation. Do you think there is or isn't much of a problem here? I found the troubleshooting section in the TM for it, so I'll work on that once it's here...

 

[Thunderbirds]

Disconnecting the TDM will force the cooling fan to stay engaged. You lose a little engine power, but it keep everything cooled like it is supposed to

Am I safe to assume they diso'ed it to keep it cooler in the desert? Just trying to make sense of it.

Thanks again, Coug.

 

[cdohner44mag]

My 1123 came with the TDM disconnected as well. Haven't really messed with it yet but I did connect it for about two seconds with engine running and it stopped the fan. Been running with it disconnected with no problems. I don't plan of fording anytime soon and I doubt the loss of 10+/- hp is going to change my 0-60 time by much. When I run out of more important things to work on I'll dig into it.

 

[Mogman]

Sometimes there is no rhyme or reason for anything that happens to a HMMWV, you are going to have to troubleshoot any issues as they pop up.
It could be that one of the components in the fan clutch circuit failed or not....

 

[juanprado]

high failure rate on this item. Many are overheated and the epoxy goo on the back is meted or melting away.
as noted unplugging it allows full cooling all the time as a fail safe.

 

[Coug]

Awesome, thank you Coug. I knew it delays and disconnects the fan, but I must have misunderstood the theory of operation. Do you think there is or isn't much of a problem here? I found the troubleshooting section in the TM for it, so I'll work on that once it's here...

You can run it forever disconnected and the only thing it will hurt is your fuel economy. As long as the thermostat is doing it's job and opening at the right temp, the engine will come up to operating temp.
In winter it would definitely be an issue though. The fan moves a LOT of air (something in excess of 10k cfm) and it's possible you won't properly warm up, and the heat inside the truck already kind of sucks. Not so big of an issue down south, but up north you'll feel the cold.