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thermo switch test / new part?

Started by briandneville, February 26, 2023, 05:46:34 PM

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I removed the thermo switch from the cooling system T joint and performed the test printed in the 11J service manual found on my hard drive (no idea where it came from, but probably this forum).  The manual states that the switch should have continuity at 96°C or higher.  Mine does not.  And it does not have continuity at any temp I can get water to before boiling (Got it up to 99.6°C).

I know the switch works, since my fan comes on after I park the bike in my garage after a ride and the engine is really hot.  I am guessing that it just comes on at a higher temp than that stated in the manual, and I guess that is ok.  Reading old threads here I see POD believes the temp range for continuity is above boiling temp and the test is therefore inaccurate / unreliable.  I also see that there is no readily available 'new' replacement part.

Does anyone know of a replacement part that fits the vision and is known to work?  I saw an old thread where a switch was put into the burb bolt housing, which seems doable, but wiring in a manual switch would likely be easier.

Any current thoughts?
How did it come to this?


Ready for a stupid question? If the switch works, why are you trying to fix it? The fan is supposed to come on when it's parked and hot to help prevent vapor lock.
Whale oil beef hooked!


Excellent question.  Engine temp climbs near red when it's 70° or warmer out.  It has never over-heated on me, but it does make me nervous.  Just wondering if the switch is working properly.  The manual had the test in it, so I tried it, and it didn't work. 
How did it come to this?


Is the fan working when the engine gets hot, and is it always in stop and go traffic? If the fan isn't working in those conditions then something isn't up to snuff. A quick and easy fix would be a manual switch to activate it before getting hot. More fan usage will put a bigger load on the charging system too so it needs to be performing well.


Fan works fine. And yes it comes on at red lights / traffic.  I'm really jsut wondering if any has ever gotten this test to work?

How did it come to this?


A coupe of things that will help with the hot running is use a more diluted mixture of antifreeze, so not 50/50. More water will help in dissipating the heat and use some water wetter in the mixture. It doesn't get really cold where you are as far as I know so a 75% water mixture should work ok.
As far as what info you are looking for I have no experience. Sorry.

The Prophet of Doom

There are discrepancies in the quoted ON range:
11U manual specifies 105+/-3 degrees C
16R manual specifies 98+/-3 degrees C

So the test might work, but then again it might not, and that doesn't mean it's defective.  Altitude will lower your boiling point as well.  95 Degrees in Denver apparently.

The red zone on the gauge is supposed to be 115 Degrees so the fan should be well on by then


Thanks for the feedback.  Will reassemble and see what happens.  New thermostat so that will potentially change things, hopefully in the right direction.  I also bought a NOS thermo switch off ebay so will see what that does in a pot of boiling water.  Still 40 years old, and likely dropped more often than the one I pulled from my bike...
How did it come to this?