M1097R1 Cooling Problem

[SailBoat]

This one is kinda of a weird one to me that is drove the truck to the shop for other reasons noticed the temp gauge was on 240. Never heard the fan kick on or off, but could feel the fan pushing air at idle and hood raised. So I suspected the TDM or the fan Solenoid cause they’re common. Got the new ones in and turn the truck on and smoked the new TDM. So I started ohm’ing and checking for voltage and have all the right reading according to the TMs. So figured it was just a bad one for sitting in my box for too long, so got a brand new one out the wrapper and smoked that one too. Im feeling like I’m over looking something but can’t put my finger on it. Also with the old TDM hooked up the fan runs constantly.

 

[Mogman]

This one is kinda of a weird one to me that is drove the truck to the shop for other reasons noticed the temp gauge was on 240. Never heard the fan kick on or off, but could feel the fan pushing air at idle and hood raised. So I suspected the TDM or the fan Solenoid cause they’re common. Got the new ones in and turn the truck on and smoked the new TDM. So I started ohm’ing and checking for voltage and have all the right reading according to the TMs. So figured it was just a bad one for sitting in my box for too long, so got a brand new one out the wrapper and smoked that one too. Im feeling like I’m over looking something but can’t put my finger on it. Also with the old TDM hooked up the fan runs constantly.

Where did you get the TDM ? there are allot of crap chicom knockoffs out there.
Also you should actually troubleshoot the issue not just throw parts at it, you can cause additional issues which make fixing the actual problem much harder.

 

[Coug]

Either you have been buying bad TDMs, or you have a short to ground somewhere in the system that is overloading it and causing the instant failure. Not much else in the system really.

Without the TDM installed, you shouldn't be having any overheating issues as the fan should be engaged 100% of the time. Only thing that would change that is a bad cadillac valve.

The fan will still move air at idle with it disengaged, but wouldn't be anywhere near as much as with it fully engaged.

The fan system defaults to engaged if it doesn't have any voltage to it. The only ways to fail to disengaged are either the temp switch on the motor or the TDM failing and providing 24V to the cadillac valve, or for the cadillac valve itself to fail and jam open. Most common of these is the TDM, after that is likely the engine temp switch. Most cadillac valve failures I've heard of were preventing the fan from disengaging, not the other way around.

If the gauge is still showing 240V with the TDM removed and confirmed that the fan is fully engaged (in the manual it pretty much just says rev the engine and see if you feel a lot of air coming out from under the truck by the driver's door) then you need to do a couple things
1) use a laser thermometer to verify the engine temp. The metal right next to the thermoswitch for the cooling fan, or the upper radiator hose right next to the block are common places. This is to make sure you don't just have a bad gauge or sender
2)Check the radiator temp. Once everything is warmed up the thermostat should open. If it doesn't open, then the engine coolant just isn't able to get rid of the heat. Again, a laser thermometer should work.

 

[SailBoat]

It’s with whoever the military orders parts from, I’m not really sure who they use. And I’ve been checking the wires trying to see if it’s shorted somewhere but haven’t found it yet everything is showing that it has the right volts and the ohms inside of the ranges given only thing I haven’t checked yet is the PCB which I will check tomorrow.

 

[SailBoat]

T

Either you have been buying bad TDMs, or you have a short to ground somewhere in the system that is overloading it and causing the instant failure. Not much else in the system really.

Without the TDM installed, you shouldn't be having any overheating issues as the fan should be engaged 100% of the time. Only thing that would change that is a bad cadillac valve.

The fan will still move air at idle with it disengaged, but wouldn't be anywhere near as much as with it fully engaged.

The fan system defaults to engaged if it doesn't have any voltage to it. The only ways to fail to disengaged are either the temp switch on the motor or the TDM failing and providing 24V to the cadillac valve, or for the cadillac valve itself to fail and jam open. Most common of these is the TDM, after that is likely the engine temp switch. Most cadillac valve failures I've heard of were preventing the fan from disengaging, not the other way around.

If the gauge is still showing 240V with the TDM removed and confirmed that the fan is fully engaged (in the manual it pretty much just says rev the engine and see if you feel a lot of air coming out from under the truck by the driver's door) then you need to do a couple things
1) use a laser thermometer to verify the engine temp. The metal right next to the thermoswitch for the cooling fan, or the upper radiator hose right next to the block are common places. This is to make sure you don't just have a bad gauge or sender
2)Check the radiator temp. Once everything is warmed up the thermostat should open. If it doesn't open, then the engine coolant just isn't able to get rid of the heat. Again, a laser thermometer should work.

thank you, and I have 24v going into the fan temp switch and 24v coming out also used a jumper wire to jump the fan switch (disconnecting and reconnecting it ) to see if it cuts the fan on and off and it doesn’t) but I will run back through everything that you mentioned above when I get back to work.

 

[Mogman]

T
thank you, and I have 24v going into the fan temp switch and 24v coming out also used a jumper wire to jump the fan switch (disconnecting and reconnecting it ) to see if it cuts the fan on and off and it doesn’t) but I will run back through everything that you mentioned above when I get back to work.

24V coming in and out of the temp switch (or jumping the leads) is trying to turn the fan OFF, it is a fail safe system so removing the 24V from the Cadillac valve turns the fan on, when the temp switch OPENS and the 24V stops going through the temp switch is when the fan runs.

So disconnecting the Cadillac valve should turn the fan on.

What does "It’s with whoever the military orders parts from" mean??

If a seller boasts they supply parts to the military I would immediately suspect they are 100% fake.

So who was this military parts supplier??

 

[Milcommoguy]

My guess is the Cadillac valve solenoid maybe shorted. Coil resistance should be in the range of 58 to 78 Ohms (wire to wire) AND check each wire of the solenoid to valve body for a shorted winding to assembly. One should NOT get a resistance measurement on this test. TOSS IT if you do. Make these two tests FIRST to avoid blowing up Time Delay Modules ,TDM's. In the case of fake parts... ALWAYS ask.

Here's the Low Down... or Cool Down in the first chapter. It's cool to be in school, read >

https://gear-report.com/wp-content/uploads/2017/03/HMMWV%20A1%20Troubleshooting.pdf

It's that time of the year for this recurring problem.

Be cool with knowldge, CAMO

 

[Gcelevator]

24V coming in and out of the temp switch (or jumping the leads) is trying to turn the fan OFF, it is a fail safe system so removing the 24V from the Cadillac valve turns the fan on, when the temp switch OPENS and the 24V stops going through the temp switch is when the fan runs.

So disconnecting the Cadillac valve should turn the fan on.

What does "It’s with whoever the military orders parts from" mean??

If a seller boasts they supply parts to the military I would immediately suspect they are 100% fake.

So who was this military parts supplier??

My understanding is he might be in service and the parts are supplied to him. I might be wrong.

 

[SailBoat]

24V coming in and out of the temp switch (or jumping the leads) is trying to turn the fan OFF, it is a fail safe system so removing the 24V from the Cadillac valve turns the fan on, when the temp switch OPENS and the 24V stops going through the temp switch is when the fan runs.

So disconnecting the Cadillac valve should turn the fan on.

What does "It’s with whoever the military orders parts from" mean??

If a seller boasts they supply parts to the military I would immediately suspect they are 100% fake.

So who was this military parts supplier??

Im sorry I’m in the military but I don’t really know where they get their parts from but when I request one it comes from one of there warehouses or another shop, I’m just trying to learn as much as I can so when it happens again I know where to start looking , ima correct myself I think the problem started when I drove it to my shop because for the first half it was fine but then it got to 240 and when I got to the shop the fan was constantly engaged I’m sorry for any confusion but with the fan constantly engaged it gets to about 200 but usually with a good tdm and or good fan solenoid you barely feel any air at idle and hear it kick in when driving it , but now it’s constantly on when it cranks up I fixed the problem for it overheating someone had the radiator cap on wrong (privates) but now I’m trying to get the fan to work properly and I can get the fan to turn off when I have the 584 ish wire (I’m not sure of the exact wire number right now) and wire number 93 plugged directly to the fan solenoid and cut on when I unplug them and I’ve replaced the fan solenoid with a working one but everytime I plug a tdm up it just burns it up but I have 24-25v coming to the tdm which is throwing me off for it to be burning up like that I hope this helps