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Discussion Starter #1
So I just got my latest '86 and its parked out in the driveway, covered. We had a little rain last night and this morning I was standing in front of the house and heard this strange blowing noise. Thought it was coming from across the street, and went back in, only to come out a while later and realize that it was my radiator fan!

The cover that came with the bike is old and worn (I haven't had a chance to go get my Nelson Riggs cover from my mothers... I'm a student and rent a house by the university). It did let some water through to the seat last night, and it doesn't fit the bike very well. I'm wondering if I got some water somewhere in the electrical components and it shorted out the fan switch. I unplugged the fan power source for now, though the brand new battery the bike came with wont even turn her over anymore (have the receipt from PO from auto-zone, it might go back as having a "bad cell"). Anyways, the questions:

1) Is this switch somewhere in the radiator assembly? I have two other radiators I could replace if this one is faulty.

2) Is this indicative of some larger electrical problem farther upstream that I'll need to fix?

3) Is it possible, though I would really rather not, to install a relay on the fan so that it will not run without the key in the on position? Could this cause any heat damage? I don't think it would, as the engine will stop producing heat once it is shut off.

4) Is it too soon to already want to take a sledgehammer to this thing?
 

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Discussion Starter #2
update

So I got back from school today and decided to take another look at the Vulcan. The radiator fan will still run continuously if I plug in the power source. If this is indeed an issue of water getting in somewhere, it will probably take a few days to dry out. I got her fired up (only running on choke) and ran her a few minutes with the fan unplugged to heat her up a bit, but the temperature gauge will not budge. Not sure if this might be a clue...
 

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there is a fan relay already. its in the junction box and is fed by one of the temp sensors. slimvulcan can elaborate and no it should not run continuously. on my basket case, someone hard wired a switch that essentially bypassed the relay and temp sensor and enabled you to switch the fan on and off as you wish. i have since restored all the connections to factory. If i am not mistaken, there are 2 temp sensors, one to drive the meter and another to activate the relay in the junction box.
 

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Some of these 750's have that issue when they get wet. Not sure of the exact cause (older wiring getting wet?) but once it dries out you should be ok. That is why you should get a good waterproof cover, or better yet park inside or under a carport, and never wash it with a garden hose.
 

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Cleaning the electrical contacts and applying dielectric grease before reconnecting should also help.
 

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Discussion Starter #6
Haha, I live in a student rental about 100 feet from the ocean. Garages are luxuries we don't have and rain and heavy fog happen a lot here, though I do have a good cover that I'll be recovering this weekend.

Another thing is that I plan on using this bike as a regular driver. If I ride to campus and a little rain shower stirs up, I'll be SOL if I come back to a bike that's been cranking the fan for several hours. I've already found a few loose pigtails up by the headlight and back by the battery, but all electrics function properly and the pigtails are all female (2 at the headlight and 2 at the battery). I figure they were for some accessories that were removed. When this weekend rolls around I'll have more time to actually give her the attention she deserves...

Any word on where I can find those two temp sensors? Wiring is not my strongest suit.

Many thanks for these helpful replies!

-Luca
 

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Linkmeister Supreme
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Temp sensor for the gauge is on the thermostat housing under the tank. Remove right neck cover and maybe tank to get to yellow connector on thermostst housing. (Test for both sensor and gauge is in service manual.)

Thermo switch for fan is on the lower left side of the radiator.
Pull off the wire connector to shut the fan off.

Charge the battery before riding, at a maximum rate of 2 amps for 4 to 5 hours.
(Ideal charging rate is 10% of the capacity of any battery, or 1.4 amps for the vn750`s 14amp hour battery. Don`t rely on the stator to recharge a dischared battery, only to keep a charged one up.

The *loose pigtails* you found at the headlight bucket and by the side cover are for powering accesories, not leftovers from unhooking something.

X2 to cleaning all connections and sealing with dielectric grease.
 

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Wareagle1970
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I had the same issue, although it was self-inflicted. I broke out my pressure washer one day to clean the rims. Well, I backed the washer off a little bit and sprayed down the rest of the bike. When drying I started noticing a clicking sound, when all of a sudden my fan comes on... The block was cold as ice. I ended up disconnecting the switch as well and let her dry that night. Took the entire next day in the sunshine for the switch to finally work correctly... Learned a valuable lesson that day. Pressure washer + motorcycle = dumbass...

I wouldn't think a regular rain shower should cause your issue. Living in the South, we often get early afternoon thunder showers in the summer. My bike has endured through all of these without the fan getting stuck on, although I rode home with a wet butt!!!
 

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Discussion Starter #9
I'll be getting some dielectric grease and checking all the wires and sensors. I have some shrink tubing I could use to seal up any bare wire or dubious connections and good sensors/gauges if I need to replace any. As for the wet butt issue, I'm pullin' the seat off the '85, since it doesn't have all those little "cups with the buttons" in it. Its much flatter, so I can wipe it off if it gets caught in the rain, and much firmer, so hopefully more comfortable on long rides. After about forty minutes I sink all the way to the bottom of the '86 seat. The '85 seat also looks a bit less like a 50's leather armchair, and the bike in question has very low rise bars... I think this will be a nice combination with them.

These forums are quite awesome! You guys are real quick to respond. Thanks again for all the good advice,

-Luca
 

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Another thing you can do is clean all the connections with emery cloth and get some spray silicone or WD-40 and spray all the wires and connections. This will help shed water and keep things dry. I do this to my bikes and snowmobiles and it works.
 

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Linkmeister Supreme
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As for the wet butt issue, I'm pullin' the seat off the '85, since it doesn't have all those little "cups with the buttons" in it. Its much flatter, so I can wipe it off if it gets caught in the rain, and much firmer, so hopefully more comfortable on long rides. After about forty minutes I sink all the way to the bottom of the '86 seat. The '85 seat also looks a bit less like a 50's leather armchair, and the bike in question has very low rise bars... I think this will be a nice combination with them.

These forums are quite awesome! You guys are real quick to respond. Thanks again for all the good advice,

-Luca
Someone also recommended using spray can *Electronic* Tuner Cleaner (or similar name, as opposed to *Electric* contact cleaner which he reported makes plastic connectors brittle).

The *leather armchair* is the Kouchasaki look. ;)
 

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I got a can of "plastic safe" electrical contact cleaner at a local auto parts store. Think it was Auto Zone.
 

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I've had to replace the fan switch twice on my 86.The last time the switch had melted the solder out of the center of the sensor and was corroded.That seemed to stop the fan running on mine.
 

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Discussion Starter #14
Well I took a look at the verses, which I probably should have done before... what can I say, I wanna get a few posts under my belt. Anyways, gave the relay a couple light whacks with my 3/8 drive socket wrench and that tripped it back. Apparently they can get stuck on if they haven't been turned on in a while. I had to take a whack at the starter one too when the starter button wasn't working. As for the carbs, I just tried the gumout up the drain plug trick. Now I just need to wait for this charger to get enough juice in her to turn over.

Didn't really get as much done as I wanted because I spent the weekend working on my 77 Mercedes 240D... she didn't quite pass inspection.

Anyways, I digress. Looks like the initial problem is solved and this thread obsolete. Thanks for all the help... I'm sure I'll be looking for more

-Luca
 
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