MEP 002a Thermo Power Unit (Activates Shutters)

bridaus

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I'm getting overheating on mine only under load, cutout switch shuts it off.

No obvious issues, but seemed like shutters were not opening (ok maybe that's obvious).

Pulled them, used a torch to heat up thermo power unit after soaking in oil, seems to work.


I guess I'm looking for either:

Part Number, and source for replacement... (good luck to me..?!)

or

A way to recondition it. I can oil it up, but it gets hot in there obviously, so over time it's just going to stick again.


Thoughts?
 

justacitizen

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is it possible that your louver control is functioning fine and that your overheat sensor is malfunctioning? are you sure it is overheating? check for mouse nests in the ductwork.
 

Guyfang

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I'm getting overheating on mine only under load, cutout switch shuts it off.

No obvious issues, but seemed like shutters were not opening (ok maybe that's obvious).

Pulled them, used a torch to heat up thermo power unit after soaking in oil, seems to work.


I guess I'm looking for either:

Part Number, and source for replacement... (good luck to me..?!)

or

A way to recondition it. I can oil it up, but it gets hot in there obviously, so over time it's just going to stick again.


Thoughts?
OK, lets get on the same sheet of music.


I'm getting overheating on mine only under load, cutout switch shuts it off.
By Cut off switch, you mean the S4, Temp switch. It shuts the set off, right?

thermo power unit
What means thermo power unit to you? Tell me what it is on the schematic.

Have you used a IR gun to read temperature? The only way to figure out what you need, is to figure out whats wrong. Will the set run for, oh, say an hour with no load, without shutting down? Then you run it under how much load, for how long, and then it shuts down? Keep in mind, the shutters do not open often. The set really needs to be hot before it happens. Since you did not put your location info in, Its hard to tell if you are someplace cool or hot.

How did you determine that it was shutting off for over heat? There are a few other safety switches that could also shut the set down. We need more info, and you need to explain a bit more about what happened.
 

Triple Jim

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I checked your profile to see what climate you're in, but can't tell. What's the temperature outdoors when it shuts off? As mentioned above, it's hard to imagine it's really overheating. On a hot summer day here in NC, when it's running the house, my 003A's shutters open maybe 1/3 of the way.
 

bridaus

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No mouse nests.

Massachusetts (sorry I'll update my profile).

It ran for 12 hours over night at just under 30 degrees F, then when it warmed up the next day (40-50 degrees), it would cut out. Let it cool for 20 minutes, it'd run for another 3-4 hours or more depending on how hard we ran it. At 30% or under (approximately) it would run forever, 50% load or more it would cut out (again cause it's load dependent, hard to get good data on it, this was a real outage).

Thermo Power Unit is it's name in the schematic, it's basically a plunger thermostat (like a car's) that pushes the shutters open when the temperature is 120 or above. I think at 140 degrees, it's supposed to be fully open.

Yes, it's shuts the engine completely down. I don't think it's the sensor, only because the shutters aren't opening, and if it's overheating, for sure the temperature has to be hot enough to open them. They should be open fully at overheat and if they are not, I could see why it would overheat.

Mostly I'd hope to replace the thermostat (Thermo Power Unit), or save it somehow.

PS: I can't find a part number either, but I think I'm not looking hard enough.

Page 121 of this manual shows the part (number 6) http://www.liberatedmanuals.com/TM-5-6115-585-12.pdf
 
Last edited:

bridaus

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Ok, I think my post is getting moderated for pasting a link to a manual in here. Removing link.

Massachusetts

No mouse nests (took off all covers)

Ran overnight for 12 hours at 30 degrees, then next day ambient at 40-50 and higher load (approx 50%) it would shut down every 3-4 hours. 20 minutes to cool down, run another 3-4 hours.

I don't think it's the sensor, simply because the shutters should open at a good load for a long run. I feel like it's truly getting hot, and the shutters should open. I won't rule it out though, but I've never seen the shutters open except when I did my test. I feel they should at some point.

I'm mostly hoping to recondition or replace it, because I think I unstuck the thing, but I think it may stick again. Maybe regular exercise will help.


PS: Page 121 of a manual I can't link here shows the unit (number 6). Manual: TM-5-6115-585-12 figure 4-4 shutter assembly.
 

jamawieb

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It has to get HOTTTTTT to shut down. If I have a unit that shuts down due to temperature, smoke is coming off the valve covers and you can't touch it. Is that a symptom your seeing?
 

GREENMV

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Do you have good oil pressure for the time that it runs before shutting down? Pressure switch could be shutting you down also. Are you recirculating hot air on your air filter assembly? Possible bad temp sensor? I like the IR that Guyfang said to check temp. I personally have seen 002a's run forever without the shutters opening when I think they should.
 

Guyfang

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Ok, I think my post is getting moderated for pasting a link to a manual in here. Removing link.

Massachusetts

No mouse nests (took off all covers)

Ran overnight for 12 hours at 30 degrees, then next day ambient at 40-50 and higher load (approx 50%) it would shut down every 3-4 hours. 20 minutes to cool down, run another 3-4 hours.

I don't think it's the sensor, simply because the shutters should open at a good load for a long run. I feel like it's truly getting hot, and the shutters should open. I won't rule it out though, but I've never seen the shutters open except when I did my test. I feel they should at some point.

I'm mostly hoping to recondition or replace it, because I think I unstuck the thing, but I think it may stick again. Maybe regular exercise will help.


PS: Page 121 of a manual I can't link here shows the unit (number 6). Manual: TM-5-6115-585-12 figure 4-4 shutter assembly.

OK, now I see what you mean by thermo power unit.

[FONT=&quot] [/FONT]
[FONT=&quot][/FONT][FONT=&quot]When the engine reaches approximately 120 Degrees, the shutters begin to open. At 140 degrees, the shutters should be completely open. The cooling system contains a high temperature cut off switch, (S4) that shuts down the engine when the engine temperature reaches 394 degrees. Partner, that's hot. You need to take temp measurements. One way to test your theory is to jump the S4. Unscrew J13, put a paper clip into pins A & B, and run it under load. You said 50% for 30 minutes and it would shut off. So run it 45-60 minutes and see if it shuts off.

I appears that you tested the Thermo unit.
[/FONT]
[FONT=&quot]
[/FONT]
(1) Thermo Power Unit Assembly. Immerse the
thermo unit into a container of oil while monitoring
the oil temperature. Plunger of thermo unit should
start to extend when temperature reaches 120° F (49°
C). Total extension at 140° F (60° C) should be at least
13/64 inch. Replace thermo unit if it does not operate
properly.


So what were the results?

 

Chainbreaker

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One way to eliminate it being the shutters is to wedge them open, or disconnect the linkage to them and prop open, after its warmed up. If it still shuts down then its not your shutters causing it to shut down. BTW, there is an adjustment procedure in the TM for adjusting the thermo unit against the roll pin as I recall.
 

Guyfang

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Roger that! But first test the thermo unit, before adjusting.

But if you can open and let the shutters snap closed, (and I seem to remember that you better be ready to remove your fingers fast!) the operation of the shutters themselves, is probably good. I worked on these sets a long time, and never saw a thermo unit go bad. Doesn't mean its not bad, but that's why you test it.
 

bridaus

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The unit was definitely hot, maybe even hott :).

No smoke off valve cover, but it was "I wouldn't touch the sucker" hot. Didn't think to pull my sensor at that time, plus it was wrapped in the ASK. which I have off now for diagnostics.


It's definitely not the oil pressure cutoff, not only do I have consistent good pressure, but I bypassed it just in case (put it back after verifying) and it still shut down.


I did have it on cold weather air filter setting, but I feel like that's just not enough to trip it, it was 30-50 degrees while this was happening, "cold enough" in my opinion.


I think I might be leaning towards the sensor, given that Guyfang has never seen one go bad and I did test it and it worked (though I oiled it first in case it was sticking, so ruined a good opportunity for verification).


Next I'll check if there is a test for the sensor, and I do happen to have a IR temp gun, but I don't have a good way to put a load on this thing without messing with the house and innocent occupants. :/
 

justacitizen

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my 002a at similar load and conditions rarely opens the louvers. might want to verify there wasn't any gasoline in your fuel. a little gasoline will make your engine run hot. get a cheap laser thermometer and confirm the temps.
 

jamawieb

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The unit was definitely hot, maybe even hott :).

No smoke off valve cover, but it was "I wouldn't touch the sucker" hot. Didn't think to pull my sensor at that time, plus it was wrapped in the ASK. which I have off now for diagnostics.


It's definitely not the oil pressure cutoff, not only do I have consistent good pressure, but I bypassed it just in case (put it back after verifying) and it still shut down.


I did have it on cold weather air filter setting, but I feel like that's just not enough to trip it, it was 30-50 degrees while this was happening, "cold enough" in my opinion.


I think I might be leaning towards the sensor, given that Guyfang has never seen one go bad and I did test it and it worked (though I oiled it first in case it was sticking, so ruined a good opportunity for verification).


Next I'll check if there is a test for the sensor, and I do happen to have a IR temp gun, but I don't have a good way to put a load on this thing without messing with the house and innocent occupants. :/
Just FYI you don't need to use the cold weather setting on the air filter, that is for sub-zero temperatures.
 

GREENMV

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I was mentioning the oil pressure because when things heat up on the unit, it could act up. The same with other old worn out parts, weak fuel pumps Etc. 394deg is definitely hot to shut it down? I am just guessing, process of elimination is one big Guess. If it is heating up? Have you cleaned and blown out the oil cooler. I have had some in the past completely clogged up with dust & dirt. How is your viscosity of the oil? Type of oil? Are you getting good air flow from the fan? I do agree to start with the Temp switch and run it with the louvers wedged open. Good Luck
 

Guyfang

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The unit was definitely hot, maybe even hott :).

No smoke off valve cover, but it was "I wouldn't touch the sucker" hot. Didn't think to pull my sensor at that time, plus it was wrapped in the ASK. which I have off now for diagnostics.


It's definitely not the oil pressure cutoff, not only do I have consistent good pressure, but I bypassed it just in case (put it back after verifying) and it still shut down.


I did have it on cold weather air filter setting, but I feel like that's just not enough to trip it, it was 30-50 degrees while this was happening, "cold enough" in my opinion.

2-8. OPERATION IN EXTREME COLD (-25°F,
-32°C).

To ensure satisfactory operation under conditions of
extreme cold accomplish the following
a. Use correct lubricating oil in engine crankcase
for temperature conditions. (Refer to figure 3-1.)
Change oil only when engine is warm.
b. Use Arctic Grade diesel fuel.
c. Keep batteries in a well charged condition.
d. Be certain air cleaner intake control is in cold
weather position



I think I might be leaning towards the sensor, given that Guyfang has never seen one go bad and I did test it and it worked (though I oiled it first in case it was sticking, so ruined a good opportunity for verification).


Next I'll check if there is a test for the sensor, and I do happen to have a IR temp gun, but I don't have a good way to put a load on this thing without messing with the house and innocent occupants. :/
.
 

Guyfang

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The unit was definitely hot, maybe even hott :).

No smoke off valve cover, but it was "I wouldn't touch the sucker" hot. Didn't think to pull my sensor at that time, plus it was wrapped in the ASK. which I have off now for diagnostics.


It's definitely not the oil pressure cutoff, not only do I have consistent good pressure, but I bypassed it just in case (put it back after verifying) and it still shut down.


I did have it on cold weather air filter setting, but I feel like that's just not enough to trip it, it was 30-50 degrees while this was happening, "cold enough" in my opinion.


I think I might be leaning towards the sensor, given that Guyfang has never seen one go bad and I did test it and it worked (though I oiled it first in case it was sticking, so ruined a good opportunity for verification).


Next I'll check if there is a test for the sensor, and I do happen to have a IR temp gun, but I don't have a good way to put a load on this thing without messing with the house and innocent occupants. :/
Something else to remember is without the ASK, or the doors that the ASK replaced, the set can very easy overheat.
 

bridaus

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Update:

Put it all back together and set the cold operation slide off.

Shutters opened this time exactly as I expected at the temperatures I measured (> 120 degrees). They did not before, and I think this was the real cause.

I think only time will tell now, I need a real outage, or for the family to head out for a while one day and I'll test it under a good solid load. I think it's going to be fine now, I really should not have run it with the cold setting on the air filter, I'm sure that was a contributing factor, as well as the shutters sticking being IMO the main cause.


Thanks for all the help!
 

Guyfang

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Good to go.

Last thing I will say is to please get the -12 TM out and read it. All kinds of things in there you can learn. Heck, I am still learning about these sets. And the first 002 I worked on was in 1973-74? Take care!!
 
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