hot frame - fan? thermosensor? coolant gauge?

I spent yesterday doing some fixes on my R/R (it was a connector, not the unit), and riding today realized that my frame is getting crazy hot.

I topped off the coolant, ran it some more, still pretty hot (which I'm guessing might have aided in my R/R issue and connector? does that make sense?). Took off the fairing and let it run for a bit in the heat, and noticed that the fan wasn't coming on, and realized that I hadn't heard the fan recently, whereas I normally notice it at stops on hot rides.

A couple of questions if anyone has experience with this issue:
1) what's the relationship with the fan to the thermosensor and coolant temp gauge? (just thinking of what else I should be checking at this time)

2) in the service manual, for testing the fan motor switch and the coolant gauge, the service manual tells me to disconnect it and "short it." How do I short these connections so I can test them?

Any tales or tips in this process would be greatly appreciated. Just hoping to order the right parts before taking off the gas tank, carbs, and radiator to work on the fix here.

Another weekend in the garage, and learning more about how to fix my 96.
But looking forward to weekends where I ride instead of fix.

cheers,
Eric

 

well on these there are 2 sensors 1 on the thermostat housing and one on the radiator itself the one on the radiator is the one that you neede to touch to the fram or ground out to see if the relay for the fan is working also check your fuses thats the first thing i do when there is an electrical issue anywhere...

 

make sure your rad cap is all the way on. usually it feels on, but another 1/4 turn makes sure it's on... you could have air in the rad and a partially installed cap wont let it "burp" . A very common problem.

 

I just double checked the rad cap (it was snug, but I undid it, and re-tightened to be sure). Also checked the fuse, and it's good.
Both good suggestions though.

Any ideas on how to "short" the connection?

Since the bike was cooled down now, I spun the fan with my finger, and it moves fine. Which just means that it's not stuck, though the motor could be dead still.

 

To 'short' the fan:
The electrical connector (for the thermoswitch) is on the lower left-hand side of the radiator. Under the rubber boot is a 90deg spade connector. Gently pull off this connector, and touch the metal to some point on the frame, like a bolt head - nothing painted. When the ignition is ON, the fan should run.

The fan is always fed +12v. Its just not always given a ground to make a complete circuit, and operate. The thermoswitch creates this ground once it senses the temperature of the coolant has reached about 220deg F. A very common mod is to add another electrical wire to the thermoswitch wire, and running it to a manual switch that is also connected to a good ground. Mount the switch on the LH handlebars within easy reach of your thumb. Presto! instant fan over-ride. Now it can be turned on at the discretion of the rider, and not waiting for the temp to climb. Handy for slow driving like in traffic jams, or if you need to idle the bike in the driveway for long periods.

 

What you describe sound perfectly normal to me. The 90-97 VFR750 frame gets very hot and is just fine.

The temerature gauge is just above the cold marker under normal riding conditions but in slow moving traffic or high ambient temperatures gets about half way and no more.

Start your bike and let it idle until the fan kicks in. The temperature gauge should read slightly over half hot when it does. If this checks out then all is well in the world and you have saved yourself a load of wated time looking for a fault that doesn't exist.

 

What Sye said- the frame on my buddy's 97 gets hot. It is the nature of the beast.

Mac