This is long, but I am trying to give you as much information as possible.
brian beal wrote:How exactly does the fan itself and the fan thermo switch work together?
Start by going to
my gallery and downloading the schematic for your bike. (Aspencade is the same as Interstate with some accessories added on. Download both the standard & Interstate versions - sometimes something shows up better on one than on the other)
(Click the thumbnail to bring up an 800x600 image of the schematic, then click the 800x600 to bring up the full size pic. Right click the full size image and click Save Picture As)
Near the middle bottom you will find the FAN MOTOR and the THERMO SWITCH next to each other (for some reason the thermo switch isn't labeled on the '80-82 Interstate drawing).
You will see a black wire connecting the switch and the motor, a green wire from the other side of the switch to ground (in the wiring harness) and a blue wire from the other side of the motor that connects to a blue/black wire that runs to a the black main power wire (not fused, on whenever the key is on).
The circuit works like this:
- One side of the fan motor is connected to power. The other side of the fan motor goes to ground through the thermo switch.
- The thermo switch is basically a switch that is normally open (no current can flow through it) at lower temperatures but it's contacts close (allowing current to flow) when it is heated up.
- The thermo switch is screwed into the thermostat housing so that one end of it is exposed to the coolant and when the coolant reaches the prescribed temperature the thermo switch closes and connects the fan motor to ground, turning it on.
In real terms:
- You will see a black rubber object about 1.5" across with two wires coming out of it on the thermostat housing . This is the plug that connects the thermo switch to everything else.
- If you pull the plug off of the switch the fan should not come on.
- If you pull the plug off of the switch and the fan still runs look inside the plug to see if someone has put in a jumper across the terminals inside the plug (this is the quickest way to bypass the switch if it fails in hot weather and you need to get the fan running).
- If the fan still runs and there is no jumper, look for a connection between the wires that run to the plug (or wires spliced to the wires that run to the plug and connected to a switch).
- If there is no jumper or connection between the wires and the fan still runs you need to have someone who understands bike wiring look at it - I couldn't begin to describe all of the possible ways someone could screw around with the wiring harness here.
- If the fan stops running when the plug is unplugged you will probably need to replace the thermo switch. This is covered somewhere else on this forum, including a car part that will work if I remember correctly.
BTW: Most fan switches fail open. This means that if the thermo switch fails the fan will not run, no matter how hot the engine gets.
It is far more likely for the switch to have failed open and someone bypassed it than for the switch to have failed closed and actually cause the fan to stay on.
if the fan itself was rigged with a "parade switch" does that mean it would completely by pass the thermo switch?
The basic idea of the parade switch is to connect a manual switch directly across the thermo switch so that you can turn the fan on manually. If you have ever been in any kind of slow procession (or even stop & go traffic) on a hot day and felt the blast of the fan kicking on & off you will understand why having it on all the time and blowing warm (but not furnace-hot) air steadily would be desirable.
As I mentioned before, parade switches were fairly common at one time, but they were by no means universal. I have also seen liquid cooled bikes that had been fitted with something similar because the thermo switch had failed and the owner felt that they could control the fan adequately by keeping an eye on the temperature gauge and switching the fan on when needed.
There were even parade switch kits available with a switch that mounted in the fairing and looked like it belonged there. I had a parade switch on my first 'Wing but I just connected a regular switch across the thermo switch and mounted a LED beside it so I would know when the fan was on (BTW: when the fan was off and I got up to about 70 Km/h the wind turning the fan blades generated enough power to make the LED glow dimly).
On the off chance that the previous owner did something like this, look for a switch that doesn't seem to do anything else and try it. Don't forget that it can take a few seconds for the fan to coast to a stop when the power to the motor is shut off.
Or If the thermo switch was rigged and not the fan motor itself how would that keep the fan on all the time as soon as the 12 volts(turning the key)occurred or could the continuous fan be only achieved by the fan motor itself being hot wired??
You have to think in terms of the whole circuit, not the individual parts of it. The thermo switch is a sealed unit so it couldn't be "rigged" to stay on. The fan motor has to be connected to power (positive voltage) and ground (negative voltage) in order to work. It is normally connected to ground through the thermo switch so there is no way to "rig" the fan to come on without connecting something across the thermo switch.
Also, remember that this is bike, not a car - when the key is turned off nothing gets power, not even the fan. If someone bypassed the thermo switch in some way the fan would be off when the key is off and it would run all the time when the key was on.
Rant: I have never understood why so many potentially battery draining circuits (lights for example) in a typical car are still live when the key is off. This is an example of bad automotive design that has become universal, but that's a rant for another time.