Fan not coming on.

[6adan]

I am working on a 77 and have it running but the cooling fan will not come on. I am getting voltage to the fan switch and I can cross the wire out and the fan runs. With the engine running it will get to the hot mark but the fan never comes on. I have changed out the switch but still the same.

[robin1731]

Put a box fan or similar in front of the bike. Not turned on. Let the bike run and let it get past the hot mark. Be ready to turn the box fan on "just in case". The gauge isn't going to be real accurate. If you jumped the switch to verify the fan works, and also swapped the switch it may just not be getting hot enough to come on.

Did you test either switch/sending unit to verify they work? Should do that too.

.

[Fred Camper]

It has to be pretty high on the gauge (past half way) to trigger the fan.

[6adan]

Thanks, the hand was at the mark all the way to the right side. I tested the switch by connecting a ohm meter and heated with a heat gun till a short was indicated. I know this is not the way the book says do it but it did work just could not tell exact temp that it turned on.

[ob1quixote]

Air bubble in the coolant passages?

[CYBORG]

With engine running I would Short across the switch/sensor and see if the fan comes on. The voltage from the switch is positive only. The ground is the second wire from the radiator. Verify that as well

[6adan]

Cyborg, I have done that and the fan dose come on. To me that would eliminate everything but the switch. I will try another switch. Could it be possible for the temp gauge to be bad and showing a false reading?

[Fred Camper]

The temp gauge is one of the users of the 7V regulator. So if the fuel gauge also looks suspect then it would point to the regulator. It is easier to replace with several new options.

[CYBORG]

until you know at what temp the switch turns on, you don't know if it is good or not. I would check the engine temp with an Infrared meter to verify the temp the sw activates at. I have converted all my bikes to direct connect sw and gauge. And the gauge reads in actual temp numbers. Old school, but very reliable

[Track T 2411]

until you know at what temp the switch turns on, you don't know if it is good or not. I would check the engine temp with an Infrared meter to verify the temp the sw activates at. I have converted all my bikes to direct connect sw and gauge. And the gauge reads in actual temp numbers. Old school, but very reliable

+1

[Don R]

I used the ebay switch with good results. Some web posts recommend a cx500 switch but it didn't fit my threads.

[6adan]

Thanks everyone, I was able to check the 7v regulator and it seems fine 12v in 7v out. I do not have an infrared meter (will have to get one) while I was working on it today I let it get to the red mark but it did not seem like it was as hot as it was reading, I loosened the rad cap and no spewing of coolant.

[Sidecar Bob]

I used the ebay switch with good results. Some web posts recommend a cx500 switch but it didn't fit my threads.

Funny you should mention that. The CX/GL500/650 fan switch has 16mm threads and the one for 4 cylinder GoldWings has 18mm threads. When I installed the "new" engine in Mr.H I bought a fan switch made for Suzuki bikes on eBay (a real bargain at $10 CAD). It seems to be a well made item but it turns on at 85 degrees instead of 95 so I changed to an old original one I had last spring. One hot evening a couple of months later when the engine overheated and left a trail of coolant on the road I was glad I had installed a "parade switch" so I could turn the fan on manually https://www.ngwclub.com/forum/viewtopic ... 20#p730190.
I got through the rest of the summer using the switch and over this winter I ordered one of these https://www.ebay.ca/itm/372859551686
When it arrived I checked the fit and they had sent me the 16mm version. I contacted the seller and they sent me the correct replacement (I now have a spare for Eccles). I haven't installed it yet because Mr.H is still in winter storage.