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Fan not coming on ...


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Hi Guys,

 

The temperature got into the mid-230s today and the fan didn't come on. I just got home so I haven't been able to look at it, but I've been able to ascertain the fan blades spin freely, so hopefully it's not the fan itself. I figure it's wither the switch or the fan. Any tricks to troubleshooting this thing?

 

Thanks,

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Check that the coolant is full. If it's low and does not cover the switch, it can not correctly sense the temp. When adding coolant, bleed the system with the bike on the sidestand to make the cap the highest point in the system. While you're at it, check the condition of the cap, replace if necessary. If coolant is full, pull the wire from the fan switch, ignition switch on. Check for battery voltage at the wire. If volts are good, ground the wire.  The fan should operate.  If all that checks out the switch may have failed.  Let us know what you find. 

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a lot of riders install a switch in parallel with the radiator temp switch to better control water temp in traffic. old thermo switches often fail.

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there's multiple points of failure. You'll want to do some testing to see where fault is:

 

1. apply power & ground directly to fan and verify it spins

 

2. test thermoswitch in pot of water being brought to boil and measure temperature when it closes

 

3. test wiring between switch and fan. Idle bike until reaches fan-switch temp and measure voltage at fan connector. Does it have power when fan-switch closes?

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2 hours ago, DannoXYZ said:

 

. Idle bike until reaches fan-switch temp and measure voltage at fan connector.

 just me........ but i don't like letting my bike sit and idle for that long.

 

i've gone through many cases of non-running fans, once a bad ground and ALL the other times a bad switch.

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Low coolant, sure as shit. The fan worked fine. The reservoir was empty and the coolant was pretty low in the radiators. I filled it up, topped off the reservoir and went for a ride. Worked like a champ. Thanks for the help, fellas. 

 

I'm kinda wondering where all my coolant went though. I haven't checked it in awhile. I'm wondering if the stain in the reservoir tricked me into thinking I had coolant when I didn't. I'll keep a closer eye on it from now on.

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If a leak isn't obvious, it could be under the throttle body.  5th gens and VTEC's have a habit of fossilizing the o-rings on the water necks coming out of the heads.   And, the hoses are now 20+ years old  . . . If you do get in there to change anything out, be sure to put in a new thermostat while you're at it. 

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Riding in hot climate I have hard time to fathom keeping 20 year old rubber on a vehicle - getting stuck on a side of the road ain't fun. V motors are bit of pain with those well hidden hoses you mentioned. My SV being 2006 and virtual not ridden still had ugly hoses sitting under throttles...

20210329-032946.jpg

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You guys are sapping my will to live with this talk of leaks. Oh well. I'm planning to do a major service in a few thousand miles. I'll take a serious look around then. 

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