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MANIC MECHANIC
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943 Posts
Discussion Starter #1
First off let me tell you about my electrical system. I have an exide supercrank sc30lfa 28ah 445cca battery a tpe rebuilt stator and a shindengen fh012aa r/r. That being said when my cooling fan runs for a while my voltage begins to drop I know electric motors can build up resistance over time and draw more current. I am going to test my fans amperage draw with a dmm and an old car battery this afternoon and was wondering if anyone else had ever checked this or if their voltage drops this dramatically with the fan on. It draws enough current that i have to bump the idle up to keep it running.
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #2
Alright I took an old car battery and hooked it up to the cooling fan with my dmm in series. the reading after 10 mins was 3.5A that doesn't seem to off to me. So I am at a loss here
 

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Premium Member
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267 Posts
What else is involved with this circuit? Is there a power relay signaled by the coolant temp sensor? Is there a way to test the draw while the fan is on the bike without an auxillary power source? Since the motor draw is within what seems a reasonable range, something else is drawing power that occurs when the fan comes on.
I will try to locate a wiring diagram.
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #4
I have a diagram I just havent had time to pick it apart yet
 

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Sparky!!!
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8,697 Posts
The fan motor draws power through the JB Fan Relay. The Relay Coils are activated by the coolant sensor making ground. In stock form, nothing else is on the circut exept the AUX Fuse. do you have any accessories wired up, and if so, what are they and how are they wired
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #6
nope just the basics I only even have 1 taillamp bulb
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #8
thats what I'm thinking
I may just eliminate the factory wiring for the fan completely, I already have for the coils, horns, r/r, taillight, and rear turnsignals
 

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Premium Member
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369 Posts
That 3.5A sounds about right. Since it was so easy to measure, I checked mine and got about 3.7A.

It should be quite easy to measure the whole current draw of the fan circuit (including the fan relay). Just remove the main fuse and connect the ammeter in it's place. Then ground either the wire coming to the fan switch at the bottom left corner of the radiator or pin 4 of the JB 10-pin connector. This switches the fan on.

If the current draw is not much higher than the fan only, then you have to start looking elsewhere.

Did you mean that the engine stops with fan on unless you raise the idle revs, or that only the voltage drops at idle? If it's only the voltage, I don't think you have anything wrong - the fan takes as much power as the headlight.
 

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I was out on a ride yesterday in hot weather and traffic - stop and go crap - the worst type of riding for our vn charging systems. My fan was cycling on and off for about 20 minutes while trying to make it to country roads. My RPMs dipped slightly each time it came on so I turned up the idle to 1500 RPM until I was clear of the traffic mess.

DT
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #11
I was out on a ride yesterday in hot weather and traffic - stop and go crap - the worst type of riding for our vn charging systems. My fan was cycling on and off for about 20 minutes while trying to make it to country roads. My RPMs dipped slightly each time it came on so I turned up the idle to 1500 RPM until I was clear of the traffic mess.

DT
ok thats more the response that i am looking for as long as mine isnt the only one that does it it must be ok
 

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Premium Member
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812 Posts
Joe since you've put in a bit if time you may want to remove the engine heat sender and measure the resistance. Stick it in boiling water and see if the ohms drop to zero or near zero. If the sender/sensor is malfunctioning it could be drawing extra current in which case it's probably heating up or at best making a bad connection with ground. You can check that with an ohm meter as well. Somehow 3.5 amps should not drop the RPM on the bike. I have 2 driving lamps at 20 Watts apiece and the 40 Watts don't drop the engine speed when I switch them on.

Good luck buddy.
 

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MANIC MECHANIC
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943 Posts
Discussion Starter #13
Joe since you've put in a bit if time you may want to remove the engine heat sender and measure the resistance. Stick it in boiling water and see if the ohms drop to zero or near zero. If the sender/sensor is malfunctioning it could be drawing extra current in which case it's probably heating up or at best making a bad connection with ground. You can check that with an ohm meter as well. Somehow 3.5 amps should not drop the RPM on the bike. I have 2 driving lamps at 20 Watts apiece and the 40 Watts don't drop the engine speed when I switch them on.

Good luck buddy.
good piont I hadnt thought about testing the sender that trips the relay
 

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You can hardly call it a sender, it is just an on/off switch for the fan relay. And obviously it is working as your fan does go on and off. The current through the relay coil is small, perhaps 0.1A.
 

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MANIC MECHANIC
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Discussion Starter #15
All in all I think I will call it normal. It only happens when its really hot
 
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