Slowly failing fan temp sensor?

[sdv003]

I have a '98 Tourer with 36K miles on it.  It has a water temperature gauge that I added.  It's hot here in Vegas (110* is not uncommon) and getting the fan turned on to keep the temperature down is vital when stopped for a traffic light cycle.  In the past, the fan would switch on at approx 210* on the gauge and run until the temp showed approx 190.  Over this summer, I've noticed that the fan comes on at a warmer temperature (especially the first time of the ride that it switches on) and is switching off at a warmer temperature as well.  It can be as warm as 230 on the gauge before the fan comes on and it switches off at 205 or so.  The temperature LED will sparkle or come on hard for a few seconds depending on how warm it gets before the fan switches on.

My question is, do these switches ever fail slowly like this?  The previous posts in the forum seem to indicate that the switch either works or it doesn't.  If not the switch, any other ideas?

Thanks.

[Steel cowboy]

Have you ever thought of installing an override switch, so that you can turn on the fan manually. I have read of some people who ride in extreme temperatures as yours doing the mod. I belive they basically ground out the wire to the thermal sensor on the radiator. Tapping into the wire from the sensor to a 2 pole switch and the other side to a ground. Turning off the switch would allow it to remain at stock setting.

[sdv003]

I haven't thought about it until now, since the switch worked fine up until recently.  It should be fairly easy, so I just might do that.

[The emperor has no clothes]

Hi, Sam. I think the manual switch sounds like good idea. But, I think I would also check out the thermostat and the fan switch also. Having the temp light flicker on concerns me. As you know it gets pretty hot here also. I've never had that issue though. We don't have much stop & go traffic here though.

[gordonv]

I am not too experienced on the temp and how it works.

But I would say most have a "sudden" problem, because they never knew there was a problem before they needed it. Most don't have a temp gauge. What they notice is that there is a time they think the fan should be on, and it's not.

No matter what you do, I would search the problem. I forget where the temp sensor is plugged into. Could this also not be an issue with the thermostat.

I would also look into changing your fluid to those waterless ones. They have a higher temp they can handle. Evans comes to mind.

Also, wasn't this summer a little hotter than normal for Vegas?

[sdv003]

It was a little hotter than normal here this summer, but is 110* really that different from 108*?     (If you're curious, no it isn't)  but the problem is very slowly getting worse.  It's definitely different from last summer, which had its fair share of hot days.  Could be the thermostat sticking some, I suppose, but the bike has no problem cooling down while the fan is running.  I'm going to pull the fan switch off and see how it acts under a controlled test.  Hopefully that tells me something.

[Ken Tarver]

I just changed one on a friends valk; after getting engine up to temp, fan came on but only run for maybe 5 seconds. Then turn off for 15 seconds, then back on for about 5 seconds again....repeated  the same over and over again. Tested with ohm meter, continuity open/close repeatedly. Replaced switch, all good now ($58). First time I had seen a faulty fan motor switch.

Ken

[sdv003]

Replaced the fan switch and it seems to be operating the fan a bit earlier.  It is cooler here, so that might be a contributing factor as well.  I'll probably need to wait until next summer to see if there is any real change.

[John Schmidt]

The probe on those sensors get gunked up pretty good over time. Before you changed it out you should have run some good cooling system cleaner through it, that often will clear it up. I have one on my 1200 that wouldn't turn on at all so I pulled it out and it was covered in crusty crap, I heated up some 50/50 antifreeze and it didn't close. I let it soak in Evaporust for a couple days, then heated up some 50/50 mix again on the kitchen stove. Worked great, just used my wife's cooking thermometer and held the sensor in the solution with the ohm meter probes. It works now, closes at 216F as designed, kicks off about a needle width above 205F...as designed. I'm putting it back in and closing the system up.

[valkyriemc]

I installed a fan override switch and a temp meter years ago on my 2k interstate. Works fine, later put in an LED in case I forget to turn it off. Typically I use it when I get off the express way and come to a traffic light rather than let it go through a heat cycle I just flip the switch on, or sitting in traffic for an extended time. I also at the suggestion of another member installed an automotive thermostat which flows more coolant than the stock model. Search is your friend.

[sdv003]

I saw both of those when I went searching.  A new thermostat will happen when I next need to tear into that part of the bike.  I also like the switch idea, especially because of the heat here, but have been too lazy to implement it.  Swapping the sensor was a 15 min effort, so I took the easy route first.