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Onan 35EK Coolant Temp on Gauge Very Low


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  #11  
Old 01-07-2018, 02:34:19 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

If you need to run it before getting a chance to do the thermostat try to keep the radiator blocked so it can run somewhat warm to help keep condensation from forming.
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Old 01-07-2018, 03:03:49 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

Doing this test carefully... Slowly remove the radiator cap while the engine is running and insert a meat thermometer or one that reads less degrees into the filler cap and read the coolant temp with the thermometer. Check that against the gauge. The coolant gauge sender is usually in the head or as said earlier in the water neck before the thermostat so it is reading the hottest coolant temp.
Has the radiator ever been rebuilt where someone might have put a LARGER core, one more row of core?
Is there a bypass somewhere on the engine say for a block heater? That bypasses the thermostat.
I can tell you from personal experience that the Ford 6 takes a lot to over-heat. I drove Econoline vans for my job at UPS and it would be 115 degrees outside in Summer by the two Lakes in my area. There were LONG road stretches where you were running the van wide open throttle with the speedo pointing straight down past 85 mph, 10-15 miles in that weather and the temp gauge NEVER moved past center where it ran all the time.
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Old 01-07-2018, 06:33:51 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

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Originally Posted by farokh View Post
Yeah, I figured I'd just have to replace the 'stat. It's just that it's a pain to do. The coolant has to be drained and the fan has to come off, which in the tight quarters, is a pain. I'll just wait until the spring.
The fan has to come off...to change a thermostat?
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Old 01-07-2018, 09:54:00 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

I already have the radiator blocked off, but not 100%. I'm going to run it when the outside temperature is a bit more normal and see what the coolant is running at and make adjustments as necessary.

I can't open the radiator cap at this point as I converted over to using a recovery tank. If I open it, it just overflows. I did measure the temp at the top of the radiator using an infrared thermometer, and it read around 120 degrees, but that was when it was close to 0 out.

I'm not worried about it overheating, I'm worried about it running too cold. The oil pan read around 160 degrees, which, in my opinion, isn't quite hot enough.

The Stant I bought (Stant 45358 SuperStat Thermostat) apparently has a lifetime warrantee. I ordered a new one, but maybe I'll get a spare from them for free. I'll give it a try
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Old 01-07-2018, 10:09:15 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

With all the cold air swirling around, I doubt the pan oil temperature is going to get warmer than that no matter what you do.

I have a thermocouple for my voltmeter that I tuck into a hose fitting or tape to something that should be as hot as the thermostat. Then I cover over it with insulation, paper towels, plastic shipping foam, whatnot. It really needs the insulation to register correctly. A point type thermometer is going to measure surface temperature and that is affected by air flow.
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Old 01-09-2018, 02:55:55 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

OK, so it's almost 40 out today here so I figured I'd play with this a bit. I took off the radiator cap and started the genset up. I watched, and there was very little coolant flow. I let it run for a bit, with a load, and the coolant started flowing, but just a little. So I went and brought out a candy thermometer I have (don't ask me why I have it, I'm never made candy in my life!), but it starts at 100 and goes up in 5 degree increments. When I stuck it in the coolant at the radiator cap, it read 175 degrees. So I unblocked the radiator and have been letting it run. The coolant at the top of the radiator is still 175 degrees and is just flowing a little bit. So, I think that the thermostat is working fine. The panel gauge still shows 125. So I looked around a bit more and I found what looks like a temp sensor on the front of the motor on the bottom of the thermostat water outlet connection. Anyone know how those sensors work? IE are they basically variable resistors that change depending on the temperature of the coolant? I can't seem to find this sensor in the parts manual for the motor that I have (194-203 CSG649ford.pdf).

Thanks for any pointers!
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Old 01-09-2018, 03:41:05 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

farokh, Good test! How I have checked sending units, though you really just did, is by taking them out, plugging the hole in the engine to not lose the coolant.
I would get a hot plate and a pan of light oil so the temp can be read above boiling. You will use your candy thermometer. You power up the gauge usually by removing it and hook it up to the sensor with jumper wires.
With the gauge powered up and hooked to the sender, you immerse the "wet" side of the sending unit in the oil as you are heating it. You read the temperature on the Onan gauge against the Candy thermometer immersed in the oil. Put the bulb of the candy thermometer in the same depth of the oil at the sending unit. So now if you find a wide discrepancy between the candy thermometer and the Onan gauge, you have to try to figure out whether the sender or the gauge is erroneous.
If the gauge on your machine is a standard 2.25" round gauge then sometimes you are ahead just replacing both with a quality one like a Stewart Warner set.

If you suspect the sender, look carefully on the sending unit for ANY numbers besides an Onan part number.
Can you post a picture of your temperature gauge?

Found two temperature senders on ebay: 193-0318 https://www.ebay.com/itm/Onan-193-03...5XdVd8&vxp=mtr

193-0104: https://www.ebay.com/itm/New-Genuine...IAAOSwhlZYuMSS
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Last edited by Motorhead; 01-09-2018 at 04:05:35 PM.
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Old 01-09-2018, 04:51:59 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

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Originally Posted by Motorhead View Post
If the gauge on your machine is a standard 2.25" round gauge then sometimes you are ahead just replacing both with a quality one like a Stewart Warner set.

If you suspect the sender, look carefully on the sending unit for ANY numbers besides an Onan part number.
Can you post a picture of your temperature gauge?

Found two temperature senders on ebay: 193-0318 https://www.ebay.com/itm/Onan-193-03...5XdVd8&vxp=mtr

193-0104: https://www.ebay.com/itm/New-Genuine...IAAOSwhlZYuMSS
Here's the gauge. It's 2.25 inches...
(I can't win. The pictures come out sideways no matter what I do )
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Old 01-09-2018, 05:12:44 PM
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

I think those are Faria gauges. Don't know much about them but you could replace it with a Stewart Warner, VDO, ect because that is a standard size.
Did you by chance ground the wire from the sending unit to ground with the set running and see if it pegs all the way to hot? That tells you that you are at the right sending unit which I think 99.9% you are and also if it doesn't peg then it may tell you if the gauge is faulty or stuck internally.
Here is their website. You may be able to contact hem and get the OHMs spread that the gauge works at and check that spread on the sending unit.
http://fariabeede.com/2-pages/home.php

Looking back at the pictures of the BACK side of your gauges, is the water temp gauge the one with the circuit board on the back of it? If that is the one then you might CAREFULLY remove and CLEAN all connections and the three nuts that hold the circuit board to the back of the gauge. Billy S or Kevin would probably know if that circuit board is for OVER-TEMPERATURE shut down. A poor, loose or dirty connection to the gauge can cause bad read out.
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Last edited by Motorhead; 01-09-2018 at 05:23:04 PM.
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Old 01-09-2018, 06:10:48 PM
farokh farokh is offline
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Default Re: Onan 35EK Coolant Temp on Gauge Very Low

Quote:
Originally Posted by Motorhead View Post
I think those are Faria gauges. Don't know much about them but you could replace it with a Stewart Warner, VDO, ect because that is a standard size.
Did you by chance ground the wire from the sending unit to ground with the set running and see if it pegs all the way to hot? That tells you that you are at the right sending unit which I think 99.9% you are and also if it doesn't peg then it may tell you if the gauge is faulty or stuck internally.
Here is their website. You may be able to contact hem and get the OHMs spread that the gauge works at and check that spread on the sending unit.
http://fariabeede.com/2-pages/home.php

Looking back at the pictures of the BACK side of your gauges, is the water temp gauge the one with the circuit board on the back of it? If that is the one then you might CAREFULLY remove and CLEAN all connections and the three nuts that hold the circuit board to the back of the gauge. Billy S or Kevin would probably know if that circuit board is for OVER-TEMPERATURE shut down. A poor, loose or dirty connection to the gauge can cause bad read out.
So I took another look at the EM-EK Service manual I have. It turns out that the board on the back of the temp gauge is for the low coolant and pre-high temperature warning lamps, depending on the gauge sender output. I'll have to dig into it, but the sensor is in a really dangerous spot if the motor is running. It's right behind the fan, just above the water pump pulley, inside the cage. I'll have to see if I can find where the wire winds up and disconnect it on the far end to work on it safely.

Once I know if it's the sender or not, then I figure out what to replace.
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