Anyone recalibrated the temperature gauge? - K-Bikes.com - Excellence in Motion
 
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post #1 of 8 (permalink) Old Jul 16th, 2019, 10:03 pm Thread Starter
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Anyone recalibrated the temperature gauge?

Has anyone attempted to recalibrate the instrument temperature gauge?

On my 2003 K1200GT part number 62112305870 TEMPERATURE INDICATOR, the reading is overstating the actual radiator temperature. At 190F, it points to the center marking. At 220F it is half way to Red from the center marking.

The bike's normal range is 190-220F. I think 190F should be a little below the center and 220F a little ab. Maybe there is a way to make the dial display better. It's annoying.

The engine is running in the specs proper range. Fans kick on at 221F that pull the temperature back down to 200F range before shutting off. All this is good except the gauge is off. I used an infrared temperature meter to see what temps the radiator really is vs the dash gauge.

Maybe practice on parted out gauge to recalibrate it. Anyone try it ? Thanks.
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post #2 of 8 (permalink) Old Jul 17th, 2019, 7:37 am
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You need the GS911 to check engine temp in real time.Accurately read at the engine head sensor and close to no4 cylinder where temp will be higher than the front cylinders.Then you can relate to the gauge readings that come from the gauge sensor below the water pump.

IR thermometer will not give you an accurate coolant temp reading.

About midway between the midmark and the red "overheat" is where the fans kick in.And where I pinstriped my gauge for reference.The fans coming on temp spec is in the manual and so is the warning light temp spec.

Overheat warning light comes on as soon as the temp gauge needle touches the first red bar.Can be tested by disconnecting the fans and letting the engine run til the light comes on.

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post #3 of 8 (permalink) Old Jul 17th, 2019, 10:41 pm Thread Starter
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Hi H96669. Good comment about GS-911 vs an infrared thermometer. The problem I have was not knowing if the BMW sensors are broken. Thus I used the infrared. GS-911 is using the same sensors for itís numbers working or not.

Below are my results of the GS-911 tool. I didnít get a picture the center mark dead on but it was a 190F.

Pictures 1, 2, 3 are the engine at 201F showing the gauge above the center mark, the GS911 stats and the infrared tool.

Pictures 4,5 are when the fans kick on at 221F. 221F is the spec for turning them ON. Notice the dial is edging near the nervous Red area. Thus the concern raised by many a K1200 rider.

Pictures 6,7 is for temps at 208F. A common view with fans OFF, good air flow.

Pictures 8, 9 for temps at 217 with fans ON. A common view as it tries to bring it down.

Pictures 10, 11 is a typical engine gauge and the tools used.

With the specs on a K1200 190-220 as normal operating temps, it would be nice to have the center mark be at the 208F temp. With fans on, it will bring it down to that mark. The result of moving the needle would have dead center be normal. That is what I am shooting for.

Call me crazy but I am thinking of getting a used gauge and monkeying with it to reset the needle down. Has anyone tried this before? An adjustment screw on the back like a water pressure gauge? Wondering before I tear into one from Ebay parts.

My bike's engine and cooling system appears to be ok. The range is 190-220F just fine. The fans kick on at 221F correctly stated and turn off at 208F. I havenít tested the redline marker but I assume it will flash when it hits 239F. That wasnít my focus.

There is a coolant sensor that I replaced to see if it was the problem. A new EOM sensor had no effect. Same readings on the dial. Same readings on my infrared thermometer.

There is a ďtemperature sensorĒ on the back of the engine block. I am told from a Kirk Johnsonís video, this sensor triggers the Fans. My fans are turning on ok, so I didnít switch out the temperature sensor.

Does anyone know if the dash gauge is reading the coolant sensor for the temperature sensor? I know, disconnect it and try it. Well, next time I pull the panels off.

Last there is a radiator thermostat on the right side radiator hose. I do have that part new but reluctant to change it. It is a devil to get at. My Left and Right radiators using the infrared thermometer shows similar temps on both sides. The thermostat is open and not my complaint with the needle.

Thanks for the comments.
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post #4 of 8 (permalink) Old Jul 17th, 2019, 11:15 pm Thread Starter
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I did some research on the coolant sensor and temperature sensor using the Clymer manual wiring diagram.

The wire from the Coolant sensor on the water pump goes to the instrument dial gauge. Changing my 17 yr old Coolant sensor (2003 K1200GT) did nothing to change the instrument gauge position. Same temperature readings, same dial position.

The Temperature sensor on the back of the engine block goes to the Motronic Control unit and more complex. It controls air/fuel mix, ignition timing, the fan relay, and the 239F Red temp zone light bulb on the instrument panel. This sensor for me is working as expected.

Need to find a donor temperature gauge to play with and set the needle back a notch.
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post #5 of 8 (permalink) Old Jul 18th, 2019, 8:00 am
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Normal operating temp for my bike is needle 1/8" below the midmark.On the open road,5,000Rpms and at ambient up to 80something Farenheit.

Bought the bike with 20k....needle was generally midmark which I thought was normal then.Cleaned the rads and ever since generally staying at 1/8" below midmark.Got to be pretty darn hot as in above 100F on the road for the needle to even touch the midmark.

Wouldn't be too hard to mount an accurate aftermarket gauge on the Ks,did that back then with the K100RS.I didn't see a need for the K1200 so I mounted an oil pressure gauge instead.

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post #6 of 8 (permalink) Old Jul 19th, 2019, 8:23 am
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I remembered something from years ago.I think the gauge sensor could be changed and that maybe could work to recalibrate the gauge?

Somewhere on the web there is a rather long list of available sensors with thread specs but also their resistance/ohms calibrations.

Tuners seemed to be up to them sensors changes.To either fool their ECUs or start their cooling fans at a lower temp than factory settings.

A lot of sensors have specs stamped right on them but I am not sure if the BMW one has such?

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #7 of 8 (permalink) Old Jul 19th, 2019, 4:59 pm Thread Starter
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That is the direction I am headed to alter the gauge.

Adding a resistor on the wire is the idea. Measure it ahead of time, add one, tinker with it. Maybe if spring loaded reposition it. I bought a used gauge on Ebay for cheap to practice. No sense wrecking my working bike for a science experiment. The coolant sensor is not wired to MCU controller to hurt anything.

So open it up, poke around with it and get some pictures. Post some results as I get around to it. Complain about German engineering, that sort of stuff.

I have a German car from 1999 that flashes a Trunk lid open when you start it. The light goes out after 20 feet of driving. Similar to our ABS warning light. I ask the dealer to fix it back then when new under warranty and their reply "that is the German design". I still have that light flashing and the Ms asks the same question every time I let her drive.
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post #8 of 8 (permalink) Old Jul 19th, 2019, 11:10 pm
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Perhaps there's another way.

Various BMW car models buffer the visible engine coolant temp gage, in particular my E46 2002 325xi. I'm told that other manufacturers including Mercedes and Mazda do the same. As long as the sensed temp is within a 130-220 degrees Fahrenheit, the gage needle will stay straight up. Problem with this is that if you engine starts to overheat, you don't know it until it's REALLY HOT, and have very little time (sometimes no time at all) before damage is done to the aluminum head and aluminum block. If that occurs, you're looking for a new engine.

The workaround is to access the coding in the ECU and modify one line of code, which on various forums is well known. It's risky (IMHO) to access the basic code of the ECU, and I'm nobody's software engineer, so I haven't done it. A local indie refused to do it, and I've let it lie for now.

Though my daughter had an overheat experience, fortunately no damage seems to have been done. I got that car for $500 anyway, so if it breaks, coast to the side of the road and call Uber.

Some creative searching should bring up several threads in which this has been discussed, and at this point I leave it up to you!

Last edited by Honolulu; Jul 19th, 2019 at 11:28 pm.
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