[bschmidtsd]

I have a 1982 Honda SilverWing that just started getting hot, so I brought the level up with coolant in the resevoir, and checked the radiator just for good measure. I also blew out the radiator with compressed air, but it had almost nothing for dirt. I am suspicious of whether or not the fan is running but can not find the wire or any drawing of the wire that would go to the fan. It is extremely hard to get into to check, since I also have a fairing on the bike. Does anyone have advice where I can check for current to the fan or be able to 'jump' it when the bike is not running just to see if fan is working?
Are there other things I need to check?

 

[The_AirHawk]

Probably the radiator fan switch - typically these are wired in-series after the fans, which are fused 12v "switched" all the time from the distribution block (occasionally the power is not run through the key switch). When the radiator reaches the trip-temp of the switch, it just grounds the line and the fans come on.

Look at the radiator tanks - it will be a "plug" in one of them that has just one wire going to it. Unplug that wire, and "ground" it to the frame with the key on (might have to use a short jumper wire jammed in the connector) - if the fan(s) don't come on, they're D-E-D, Dead, or you've got a fuse burnt-out or a wiring problem (mice or the like).

If they come on, plug it back in and start the bike - once it gets warm, if they don't come on, it's the switch. Replacements for vintage bikes seem to be persona-non-grata in the US, apparently. Most people just rig up a toggle switch that grounds that wire someplace easy to reach, and flip it on and off in traffic.

 

[bschmidtsd]

Probably the radiator fan switch - typically these are wired in-series after the fans, which are fused 12v "switched" all the time from the distribution block (occasionally the power is not run through the key switch). When the radiator reaches the trip-temp of the switch, it just grounds the line and the fans come on.

Look at the radiator tanks - it will be a "plug" in one of them that has just one wire going to it. Unplug that wire, and "ground" it to the frame with the key on (might have to use a short jumper wire jammed in the connector) - if the fan(s) don't come on, they're D-E-D, Dead, or you've got a fuse burnt-out or a wiring problem (mice or the like).

If they come on, plug it back in and start the bike - once it gets warm, if they don't come on, it's the switch. Replacements for vintage bikes seem to be persona-non-grata in the US, apparently. Most people just rig up a toggle switch that grounds that wire someplace easy to reach, and flip it on and off in traffic.

Thanks very much for the reply. You offered some good things to check out. Believe this or not, since I posted my problem, I took the bike out on a 25 mile drive, and can not get it to overheat. Go figure!
I am still going to check out a couple of the points you made. Much appreciated.

 

[gunsmoker]

Probably the radiator fan switch - typically these are wired in-series after the fans, which are fused 12v "switched" all the time from the distribution block (occasionally the power is not run through the key switch). When the radiator reaches the trip-temp of the switch, it just grounds the line and the fans come on.

... [if the switch is bad] Most people just rig up a toggle switch that grounds that wire someplace easy to reach, and flip it on and off in traffic.

I also had problems with my '96 Honda Shadow's radiator fan coming on intermittently, and not coming on and staying on during the time that the bike was nearing maximum temperature.

This summer it exceeded maximum temperature several times and the red temp light came on, and when I stopped I noticed I was losing coolant from the overflow tank tube.

Because all of the fan blades were black and it's hard for me to see them and tell whether it was running or not, I'm not sure how often the fan was coming on (but I don't think it was often enough).
So I did two things :
I painted every other blade of the six bladed fan white,
and
I installed a toggle switch to manually ground the fan to the frame and complete the circuit so that it will always come on if the key is in the ignition and the toggle switch is set to the "on" position.

I have not ridden the bike for any real trip since I did this, but it seems to work successfully from testing it by letting it idle in my driveway for a while.

The fan blades are easy to see now because they are alternating white and black, and when the thing is spinning it gives the appearance of a light gray color fan.