HMMWV Thermostatic Coolant Fan Switch Variants?

[O18]

I have a coolant system question (which I know this board loves!) related to the Thermostatic Coolant Fan Switch's: are there variants?

I have a 2001 M1097R1 with the 6.5 L Engine. On a recent trip the engine overheated and diagnosed it back to the Thermostatic Coolant Fan Switch not engaging the fan.

I went online and bought the following switches off of Midwest Military Equipment not knowing which one I needed. Although the pictures look slightly different both sensors came in the same size/shape.

Replacement Thermostatic Coolant Fan Switch (think this is just a pulled part)
HMMWV Thermostatic Coolant Fan Switch (think this is an OEM re-manufacture)

Here are the issues that I encounter which makes me ask if there are variants:

1. I have attached a photo of where the original sensor/switch was pulled from (to confirm it is the correct part)
   1. Note how the sensor sits relatively flush against the housing
   2. if memory serves me the fan would kick on at 220-230(?) when working
2. I have attached a picture of the sensor pulled out verses what was received
   1. As seen the thread location and pitch are very different
   2. When I install the new one, I can maybe get 1-2 threads in before I meet stiff resistance, but it does screw in
   3. The old sensor goes in, with applicable resistance, and out (indicating cross threading is not an issue)
3. In an effort to get back up and running I installed the HMMWV Thermostatic Coolant Fan Switch
   1. As seen compared to the original sensor the new one protrudes out a significant amount (it is as tightened as much as I am willing to get it)
   2. The sensor DOES kick on the fan - HOWEVER the fan does not kick on until 240 degrees
   3. The fan kicking on at 240 degrees is causing overheating issues, especially at slow speeds, which makes me not want to drive it

While not an originalist I am just trying to get the proper Switch to get on the road. Not currently looking for the fan delete kit or trying to run the engine colder than the OEM specs.

Does anyone have any insights? Is there another Thermostatic Coolant Fan Switch I should try?

Thanks in advance!

 

[Mullaney]

I have a coolant system question (which I know this board loves!) related to the Thermostatic Coolant Fan Switch's: are there variants?

I have a 2001 M1097R1 with the 6.5 L Engine. On a recent trip the engine overheated and diagnosed it back to the Thermostatic Coolant Fan Switch not engaging the fan.

I went online and bought the following switches off of Midwest Military Equipment not knowing which one I needed. Although the pictures look slightly different both sensors came in the same size/shape.

Replacement Thermostatic Coolant Fan Switch (think this is just a pulled part)
HMMWV Thermostatic Coolant Fan Switch (think this is an OEM re-manufacture)

Here are the issues that I encounter which makes me ask if there are variants:

1. I have attached a photo of where the original sensor/switch was pulled from (to confirm it is the correct part)
   1. Note how the sensor sits relatively flush against the housing
   2. if memory serves me the fan would kick on at 220-230(?) when working
2. I have attached a picture of the sensor pulled out verses what was received
   1. As seen the thread location and pitch are very different
   2. When I install the new one, I can maybe get 1-2 threads in before I meet stiff resistance, but it does screw in
   3. The old sensor goes in, with applicable resistance, and out (indicating cross threading is not an issue)
3. In an effort to get back up and running I installed the HMMWV Thermostatic Coolant Fan Switch
   1. As seen compared to the original sensor the new one protrudes out a significant amount (it is as tightened as much as I am willing to get it)
   2. The sensor DOES kick on the fan - HOWEVER the fan does not kick on until 240 degrees
   3. The fan kicking on at 240 degrees is causing overheating issues, especially at slow speeds, which makes me not want to drive it

While not an originalist I am just trying to get the proper Switch to get on the road. Not currently looking for the fan delete kit or trying to run the engine colder than the OEM specs.

Does anyone have any insights? Is there another Thermostatic Coolant Fan Switch I should try?

Thanks in advance!

.
If you disconnect the coolant fan switch, the fan should turn on and run 100% of the time...

 

[Thunderbirds]

240 degrees is a bit too high for my liking. My original comes on at 215-ish. Me too will be replacing this soon as my switch fails to disconnect at times, cooling the fluid all the way down to 150 or so before it comes back to normal temp. but only intermittently.

The aftermarket switches will be hit and miss, could be anywhere between 185 and 240, as far as I read online...

 

[juanprado]

The switch looks chinesium. On a critical part like that I would recommend oe from kascar,mac,hpg

 

[Thunderbirds]

I have a coolant system question (which I know this board loves!) related to the Thermostatic Coolant Fan Switch's: are there variants?

I have a 2001 M1097R1 with the 6.5 L Engine. On a recent trip the engine overheated and diagnosed it back to the Thermostatic Coolant Fan Switch not engaging the fan.

I went online and bought the following switches off of Midwest Military Equipment not knowing which one I needed. Although the pictures look slightly different both sensors came in the same size/shape.

Replacement Thermostatic Coolant Fan Switch (think this is just a pulled part)
HMMWV Thermostatic Coolant Fan Switch (think this is an OEM re-manufacture)

Here are the issues that I encounter which makes me ask if there are variants:

1. I have attached a photo of where the original sensor/switch was pulled from (to confirm it is the correct part)
   1. Note how the sensor sits relatively flush against the housing
   2. if memory serves me the fan would kick on at 220-230(?) when working
2. I have attached a picture of the sensor pulled out verses what was received
   1. As seen the thread location and pitch are very different
   2. When I install the new one, I can maybe get 1-2 threads in before I meet stiff resistance, but it does screw in
   3. The old sensor goes in, with applicable resistance, and out (indicating cross threading is not an issue)
3. In an effort to get back up and running I installed the HMMWV Thermostatic Coolant Fan Switch
   1. As seen compared to the original sensor the new one protrudes out a significant amount (it is as tightened as much as I am willing to get it)
   2. The sensor DOES kick on the fan - HOWEVER the fan does not kick on until 240 degrees
   3. The fan kicking on at 240 degrees is causing overheating issues, especially at slow speeds, which makes me not want to drive it

While not an originalist I am just trying to get the proper Switch to get on the road. Not currently looking for the fan delete kit or trying to run the engine colder than the OEM specs.

Does anyone have any insights? Is there another Thermostatic Coolant Fan Switch I should try?

Thanks in advance!

.
Just a thought after re-reading your post. Now that the sensor is sticking out just a bit more, is it possible you have an airpocket between the coolant and the sensor? That would account for some higher temps. I was pondering the depth that you have the sensor into the manifold. That difference could be trapping some air, and air would insulate the sensor from the fluid and temperature...

Just thinking out loud.

 

[Milcommoguy]

REM Products is a high quality thermo switch preferred in this application, OEM to say. Blue aluminium anodized label is their product. Not cheap either. Now it could be a knock off... like many other parts HumV ? They were in Tucson, AZ

Real deal or not ??? CAMO

 

[Retiredwarhorses]

are you truly isolating the issue to the switch? 75% of the time, it’s the switch, but the TDM and cadillac valve solenoid make up the remainder…
What happens when the tdm is unplugged?

 

[O18]

are you truly isolating the issue to the switch? 75% of the time, it’s the switch, but the TDM and cadillac valve solenoid make up the remainder…
What happens when the tdm is unplugged?

If you unplug the TDM the fan kicks on.

Apart from it looking (and fitting) different the cooling system does work with the updated fan switch. With the fan kicking on at 240 makes me think the switch might be set for another application or maybe i just got the wrong one.

 

[O18]

.
Just a thought after re-reading your post. Now that the sensor is sticking out just a bit more, is it possible you have an airpocket between the coolant and the sensor? That would account for some higher temps. I was pondering the depth that you have the sensor into the manifold. That difference could be trapping some air, and air would insulate the sensor from the fluid and temperature...

Just thinking out loud.

Not beyond the realm of possibility - however I briefly ran the engine with the sensor our and there is a lot of flow with the coolant. Almost instantly coolant was shooting out of that port 8-12". I do not believe that an air pocket is being created based on that test.

 

[O18]

.
If you disconnect the coolant fan switch, the fan should turn on and run 100% of the time...

Did that to get out of a bind - but would like a slightly more permanent solution.

 

[Mogman]

If you unplug the TDM the fan kicks on.

Apart from it looking (and fitting) different the cooling system does work with the updated fan switch. With the fan kicking on at 240 makes me think the switch might be set for another application or maybe i just got the wrong one.

Have you actually confirmed the temp gauge is accurate? they are notoriously inaccurate.

 

[O18]

Have you actually confirmed the temp gauge is accurate? they are notoriously inaccurate.

No...I did make an assumption that it was accurate (being new). Suppose I believe the fitment / difference from the original may be causing the issue

 

[Mogman]

No...I did make an assumption that it was accurate (being new). Suppose I believe the fitment / difference from the original may be causing the issue

Get a laser temp gun and shoot the thermostat housing, it is unlikely the spacing (depth of the sending unit) has any real effect.