Temperature Gauge Does Not Register Coolant Temperature By carefulrider (Read 944 times)

[carefulrider]

Hello All:

The temperature Gauge on my 2006 JMStar/Jonway VIVA YY250T-2, 244 cc (copy of Honda CN250, upright or vertically oriented) engine does not work. I did find the connector of the sending unit disconnected from the 'pin' on the thermostat assembly at the cylinder head. I pushed the connector over the pin, started the engine, waited 5 minutes while the engine ran, but the gauge did not register any temperature & the pointer did not move at all.

Please suggest what I should do to have an operating temperature gauge again.

[alleyoop]

First thing I would do is get a new sending unit.
Alleyoop

[carefulrider]

Thanks for the input, Alley: Last eve, I removed the coolant filler cap, started the engine, & immersed a finger into the coolant at the filler neck, as the engine warmed up. The coolant temperature at the filler neck did not rise & remained unchanged until I felt I needed to turn the engine off as I was feeling the radiated heat from the engine on my leg, as I stood beside the scooter; did not want to over heat the engine.

I concluded that the coolant was trapped in the engine block & was not flowing through the thermostat & out to the rubber hose leading to the radiator.

I then removed the rubber hose & found it clogged. Clearly, I needed to remove the thermostat housing to clean it & inspect the thermostat. However do you have any tricks to remove the thermostat housing from the cylinder head? It rotates, but it won't come out of the cyclinder head. Hopefully you have some techniques to get the beasty out!

I now have to learn how to flush a coolant system; never done it.

[ellpee]

" However do you have any tricks to remove the thermostat housing from the cylinder head? It rotates, but it won't come out of the cyclinder head. Hopefully you have some techniques to get the beasty out!"



For clarification, I'm pretty sure the thermostat and the temperature sending unit are two different animals. At least they are on my scooters. The gizmo with the pin that you mentioned is the sending unit, and all it does is tell the temperature gauge how hot the coolant is getting, whereas the thermostat allows the coolant to circulate when the temperature gets high enough. From your two posts I'm confused about which one you're talking about. The bit quoted above SOUNDS like you're actually talking about the sensor, not the thermostat housing. Am I misunderstanding?

[alleyoop]

Here you go:
Alleyoop

[carefulrider]

Thank you both: I do see where the temperature sending unit & the thermostat are different items. I was able to pull the thermostat housing assembly off with a pair of pliers. Upon examination I saw that the tube section that fits into the engine block was clogged.

So now I think I need to use a flushing compound & flush the engine block out. Shall have to find a flushing compound first. Never done it before, so don't know exactly what flushing compound to look for. Shall muddle through it, I expect.

[rks]

Any auto parts store will have a flush kit....they come with a full set of instruction. After reading the above posts, I have no doubt.... that for you.....the job will be a walk in the park

[ellpee]

Interesting picture, Alley. On my Magnum the sensor is screwed into the cylinder head or engine block or something, nowhere near the thermostat; I see from your picture that on some scoots the sensor screws into the thermostat housing. Learning is a lifelong process.

[carefulrider]

Ordered, received & installed a new thermostat & temperature sending unit assembly. The temperature gauge only registers to the first graduation mark, when the fan motor switches on. The temperature gauge pointer never goes beyond & above the first graduation mark. The fan turns on & off regularly. Somewhere I read about connecting resistors to make the temperature gauge appear more realistic. Now I have to find those posts!

Here, below, I've linked to a photo that shows the upper most position of the temperature gauge pointer. When the pointer reaches this position, the fan motor begins to cycle on & off, so the pointer never goes above this position.




Gosh, I've tried to locate those posts on the resistors, & I just haven't been able to find them again. Always something!

[alleyoop]

Yea that pic is of a 244 Helix clone and as you well know the Chinese can make changes in a second and I think they sometimes do just to cause us grieve (HAHA).
Alleyoop

[ellpee]

Oct 19, 2014 7:46:49 GMT -6 carefulrider said:

Ordered, received & installed a new thermostat & temperature sending unit assembly. The temperature gauge only registers to the first graduation mark, when the fan motor switches on. The temperature gauge pointer never goes beyond & above the first graduation mark. The fan turns on & off regularly. Somewhere I read about connecting resistors to make the temperature gauge appear more realistic. Now I have to find those posts!

I think you might find that the calibration of the sensor and the gauge can vary, so while the old sensor might have show the temp at 50% before the fan kicked in, the new one might only show 25% or whatever. As long as the fan indeed kicks in and keeps the coolant temperature where it needs to be, if it were me I wouldn't obsess too much about it. HOWEVER, if the gauge doesn't budge at all as the engine warms up, time to worry a little, sensor might be defective or bad connections.

[rks]

Ellpee is right, sending units are brand and/or temperature range specific. When I installed a 100* to 300* VDO oil temp gauge in my scooter, I had to order the right VDO sender for it. One for a different temp range gauge would give false readings....Same results if I had installed a sender intended for a Stewart Warner gauge.

I may be wrong on this...but I don't think you can correct your problem by adding a resistor, for I believe it is the resistance dropping as the sender heats up, that causes the gauge to rise.

[ellpee]

That's my understanding too from googling -- sensor provides the GROUND for the gauge, and current flow varies as temperature increases.

[carefulrider]

Okay, thanks people. No resistors. I'll just try another sending unit, & if it doesn't make the pointer go any higher, I'll live with it, as you suggest.