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Old 10-23-2014, 02:46 PM   #1
DetourJournal OP
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How to test a temperature sensor?

I believe the temp sensor is bad on my R1150gs.
I went to start the bike on a cold night and with each crank of the engine, the bars on the digital temp gauge would go up one bar, so after about 8 cranks the gauge was maxed out and made the bike really hard to start. When I did get it started it ran really rough.
I have a couple questions:

1) is the temp sensor the likely culprit? I hear the throttle positioning sensor can also be to blame.

2) How can I test either sensor it to see if it's defective? Is there an ideal resistance range they should measure up to?http://www.advrider.com/forums/showthread.php?t=95457

DetourJournal screwed with this post 10-23-2014 at 05:17 PM
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Old 10-23-2014, 03:56 PM   #2
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the bars on the RID digital temp gauge are from the oil temp sensor I think.

I am unsure where it is, there is one just behind the oil site glass, that is either pressure or temp, most likely pressure if I had to guess.

the temp sensor in the air box is for the fuel injection computer brain to decide how much petrol to squirt in regards to incoming air temp ( among other things)
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Old 10-23-2014, 04:01 PM   #3
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this might help also

http://www.advrider.com/forums/showthread.php?t=197616

or this

http://www.advrider.com/forums/showthread.php?t=505465
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Old 10-23-2014, 05:20 PM   #4
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That was actually very helpful in locating the temp sensor. I also commend you for answering my unfinished post that I accidentally posted I mid sentence.

Any thought on how to test it before I but a new one?
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Old 10-23-2014, 05:36 PM   #5
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one of those had a chart showing temp vs resistance right?

stick an ohm meter on it measure the resistance at room temp
in boilin water and then with a bic lighter on it maybe?

not scientific but should give you an idea

in my experience those types of temp sensors are usually only accurate to within 10-20 degrees

it shows about right at a few points along the scale it's probably fine

more likely a dirty connection or bad ground to the circuit making it act erratic
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Old 10-23-2014, 07:00 PM   #6
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Quote:
Originally Posted by DetourJournal View Post
I believe the temp sensor is bad on my R1150gs.
I went to start the bike on a cold night and with each crank of the engine, the bars on the digital temp gauge would go up one bar, so after about 8 cranks the gauge was maxed out and made the bike really hard to start. When I did get it started it ran really rough.
I have a couple questions:

1) is the temp sensor the likely culprit? I hear the throttle positioning sensor can also be to blame.

2) How can I test either sensor it to see if it's defective? Is there an ideal resistance range they should measure up to?http://www.advrider.com/forums/showthread.php?t=95457
MOF has made some good suggestions. As you wondered, yes Oil Temp sensor performance is critical for proper starting. It can take 3 or 4 minutes before the engine is warm enough for the O2 sensor to provide a reference.

The behavior of your gauge and poor starting shows a problem. If you could borrow a gs-911 you could know right away how the Motronic is interpreting the sensors, no guesswork. That would be my best advice.

You may also have a wiring harness problem. I think that is about equally likely based on your symptoms.
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Old 10-24-2014, 06:53 AM   #7
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Also, if you test the NTC thermistor (both air and oil temperature are measured using NTC thermistors) with an ohm meter, remember, you are imposing a current across the device which will self heat the sensor and render an inaccurate reading of R vs T. You'll need a VOM with very high ohms to volts performance so as to limit self heat.
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Old 10-24-2014, 10:44 AM   #8
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Quote:
Originally Posted by mouthfulloflake View Post
one of those had a chart showing temp vs resistance right?

stick an ohm meter on it measure the resistance at room temp
in boilin water and then with a bic lighter on it maybe?

not scientific but should give you an idea

in my experience those types of temp sensors are usually only accurate to within 10-20 degrees

it shows about right at a few points along the scale it's probably fine

more likely a dirty connection or bad ground to the circuit making it act erratic
As for as accuracy, thermistors used for temperature measurement application can be very accurate without high cost. We routinely used NTC thermistors with a 0.2 C. accuracy specification. These thermistors cost ~$1.00 each in lots of 1000.

I suspect that the BMW thermistors for air and oil temperature measurements are accurate to 2-3 deg. C.

NTC thermistors follow the Steinhart- Hart equation regarding response. I would avoid heating with the flame of a Bic butane lighter...you could melt the actual thermistor junction, destroying it.
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Old 10-24-2014, 10:51 AM   #9
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NPT vs PTC

Quote:
Originally Posted by def View Post
As for as accuracy, thermistors used for temperature measurement application can be very accurate without high cost. We routinely used NTC thermistors with a 0.2 C. accuracy specification. These thermistors cost ~$1.00 each in lots of 1000.

I suspect that the BMW thermistors for air and oil temperature measurements are accurate to 2-3 deg. C.
Just 4 the fun, now explain the difference NTP vs PTC.


Not 4 me but for the crowd.

Have a nice weekend and I will be on my way to FL 4 a week.
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Old 10-24-2014, 11:08 AM   #10
def
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Just 4 the fun, now explain the difference NTP vs PTC.


Not 4 me but for the crowd.

Have a nice weekend and I will be on my way to FL 4 a week.
PTC or positive temperature coefficient thermistors exhibit an increase in R as T increases. These devices are used in protection circuits in power supplies to eliminate high inrush or smooth the power. The PTC device is non-linear.

NTC or negative temperature coefficient thermistors exhibit an increase in R as temperature decreases. These devices are used for low cost temperature detection in toasters, hair dryers and automotive applications where accurate temperature measurement and reliability are necessary.

Enjoy Florida.
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Old 10-24-2014, 10:34 PM   #11
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Very likely Def, sorry if I was giving bad info.

I was assuming it was a sensor like an old Ford/Chevy truck.

they never seemed to be accurate or fragile to me.




Quote:
Originally Posted by def View Post
As for as accuracy, thermistors used for temperature measurement application can be very accurate without high cost. We routinely used NTC thermistors with a 0.2 C. accuracy specification. These thermistors cost ~$1.00 each in lots of 1000.

I suspect that the BMW thermistors for air and oil temperature measurements are accurate to 2-3 deg. C.

NTC thermistors follow the Steinhart- Hart equation regarding response. I would avoid heating with the flame of a Bic butane lighter...you could melt the actual thermistor junction, destroying it.
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Old Yesterday, 05:07 AM   #12
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Quote:
Originally Posted by DetourJournal View Post
I believe the temp sensor is bad on my R1150gs.
I went to start the bike on a cold night and with each crank of the engine, the bars on the digital temp gauge would go up one bar, so after about 8 cranks the gauge was maxed out and made the bike really hard to start. http://www.advrider.com/forums/showthread.php?t=95457
There is a lot of damping of the RID temperature bargraph. If the sensor is stuck at a higher reading, it could act as you described.
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Old Yesterday, 06:49 AM   #13
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There is a lot of damping of the RID temperature bargraph. If the sensor is stuck at a higher reading, it could act as you described.
Interesting. That means a broken wire might also so that or an open sensor (internally) or a short to ground?
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Old Yesterday, 06:54 AM   #14
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Originally Posted by roger 04 rt View Post
Interesting. That means a broken wire might also so that or an open sensor (internally) or a short to ground?
IIRC, open circuit=low temp.
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Old Yesterday, 07:39 AM   #15
roger 04 rt
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IIRC, open circuit=low temp.
Okay then if his sensor is slowly creeping up, it might mean something is shorted.
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