I just purchased a '91 K100RS and am in the process of getting it road ready. I've just replaced the ABS, Hazard and right handlebar combo switches and now I'm trying to clean up the coolant system. I just drained the coolant and added vinegar for a flush. I started the bike to let it flow through the system and noticed the temperature gauge shows absolutely ZERO (NADA), even after running it five minutes or so. Since I'm not familiar with the K100RS, I'm not sure how quickly it should start registering. Can someone with a K100 let me know how quickly it should rise to normal in 70 degree weather? I'm going to assume it's probably broken so I'm hoping to understand the system to better fault isolate. Thanks.

As a point of mention, I can't even locate the temperature gauge in the Clymer's wiring diagram. I must be losing it.

Is this the temperature gauge on the right side above the knee pad? Mine has one and it too does not register, though it used to. I think there's too much corrosion on the outside of the sensor which is the coolant drain plug on bikes that don't have this gauge. The wires on mine also got a bit singed when a wire broke off the back of the gauge and went full short circuit, it blew several fuses until I tracked that particular fault down.

It's an extra and not the best. If your RS is a 16v and they're different then I'm sorry for rambling but I kinda hate mine

Snod Blatter wrote:Is this the temperature gauge on the right side above the knee pad? Mine has one and it too does not register, though it used to. I think there's too much corrosion on the outside of the sensor which is the coolant drain plug on bikes that don't have this gauge. The wires on mine also got a bit singed when a wire broke off the back of the gauge and went full short circuit, it blew several fuses until I tracked that particular fault down.

It's an extra and not the best. If your RS is a 16v and they're different then I'm sorry for rambling but I kinda hate mine

Yes, the temperature gauge on the right above the knee pad. I'm a firm beleiver that if there are lights and gauges on a bike, they should be in working order. I looked in the diagrams provided in the Clymer manual and I can't even find the temperature gauge. Not sure what gives. I'm hoping to find out how to troubleshoot it properly to see if the sensor is bad or the gauge is bad.

Just sitting at idle mine will take quite a while to register but 5 mins ought to be enough. Riding, it starts to move after a very short distance and comes right up to the middle of the gauge after a couple of miles.

First thing to try would be unplug/replug the connector, maybe with a bit of contact cleaner.
You can test it on the bench. There are 4 wires: ground, 12V, sensor, backlight. Easy enough to identify from Clymer diagram. Can't remember which way it goes now but wire up 12V and ground then connect the sensor input direct to ground or 12V and it will jump immediately into the red - dead short doesn't seem to hurt it. If you can repeat with a 220 Ohm resistor it should register into the upper third.

Various topics on this forum about temperature sensor characteristics.

8V gauge works fine on 16Vs.

Good advice above, I'd just like to add that the wire between the sensor and the gauge is a poxy little thing that has a blue plastic kind of bullet connector in it which is hidden under the tank, if you'd like to clean that too.

Here's my thread for when the wire fell off the back of the gauge, it could be that your negative wire has broken off so you are spared the blown fuses. It's probably not that at all but it is worth considering, I wouldn't have believed it either until I saw it myself.

Thanks for the tips. That gives me something to check in the morning. One big thing.... I see no diagram in the Clymer that shows the wiring for the WATER TEMPERATURE GAUGE nor the FUEL GAUGE for that matter. Can you please reference the diagram to which you are referring...or better yet, snap a picture of the gauges on the diagram you're looking at and post here along with their page number. Maybe my Clymer is different from yours. Thanks.

Aux. Gauges schematic



Exploded Parts Diagram



Attachment cable #8 above.

The sensor is under the waterpump, loose it a bit and tighten again (ground)
Play with the connector on the plug, to get better contact.

The sensors for the 2V and 4V look the same, but are different.
In case you need a new one, take care you order the right one.

And, as always.....clean earthlines and connectors.

dao wrote: I see no diagram in the Clymer that shows the wiring for the WATER TEMPERATURE GAUGE nor the FUEL GAUGE for that matter. Maybe my Clymer is different from yours. Thanks.

Your Clymer is just like my Clymer; those gauges and their wiring are not depicted. In addition to the helpful resources that robmack has provided, more useful diagrams are available at this link in the K100-forum's Portal Tech Page.  The diagrams themselves do well in showing locations and wire routing. The text accompanying them is in German but if your progress is stalled by that, you could transcribe some of it into Google Translate to get clarity.

Have a PDF about the instruments, it's German with English translation;

http://forum.kforum-tech.com/members-upload/uploads/DE_-_Zusatzinstrumente_temp_en_benzinemeters.pdf

Arlina wrote:... The sensors for the 2V and 4V look the same, but are different. ... .

Arlina, the temp sensor for the auxiliary temperature gauge is not the same as for the temp module and ECU. The only criteria that must be met for that sensor is that it have the proper length (not too long so that it won't interfere with the impeller) and thread, and that it is compatible with the gauge.

Robert, seems we misunderstand eachother somewhere...  

Temp sensor for gauges of the K75 K100 2V; 62161459270

Temp sensor for gauges of the K1 K100 4V and K1100 ; 62162325348


And a mistake in this diagram, the schwartz (black) von tempgeber must be TO tempgeber (tempsensor), it's 1 wired sensor to earth (masse).

Thanks for the diagrams and links to other reference material. I located the connectors under the tank and checked those. All wires are good and are making good contact. Source voltage and light voltage to both gauges read okay on my Fluke.

Before I get back to this, I've got to find out why the fuel pump is no longer coming on.