Running Cold?

[MotoRandy123]

I was riding around yesterday and the scoot felt a bit funny. It sometimes
stumbled when coming to a stop and also when first accelerating. Some other
scoots have had a problem with the cold and they've taken to putting a piece
of cardboard blocking the radiator (just like the old busses).

I'd like to mount a temp gauge but I'm not sure if they all use the same temp
 sensor. I took this info out of the service manual (Yager on top and Grand
Dink 250 on bottom).

 The Grand Dink manual says to test the display ground the sensor line and all
dots will light on the dash. So we need to see 150 to 10 ohms? Anybody know
anything about temp sensors? I imagine we could get a meter movement and
a few resistors and make our own?



I'd guess 50 ohms is cold and 30 ohms is hot?

 The thermostat begins to open at 80C and is full open at 90C. The fan turns on
at 90C Hmm that doesn't seam right, the fan turns on when we are warmed up?

[Zimmerman]

Randy

Thermistor components were fairly cheap years back.  I bought a bunch for experimentation.  I'll dig around during thanksgiving, if I find them I'll snail mail a few.

Thermistor are temp sensitive resistors of a sort - by design their resistances vary depending on temp.  The component OEMs publish a ohm vs temp chart, etc

Anyway for basic testing put the thermistor in series with a regular resistor to make a voltage divider.  This will limit current flow - minimize supply loading & keep the thermistor cool. There are several ways to skin a cat, but I like to measure the voltage drop across the normal fixed resistance resistor while the thermistor is exposed to a range of temps. Then calculate the resistance of the thermistor over a range of test temps that you know.  See if the OEM chart is accurate.

To increase accuracy, use a Wheatstone bridge circuit - it resembles a bridge rectifier circuit lay out with two thermistors each in of the opposite legs.  I'm going from memory here but that's enough info to help someone find details on the Internet.

. . . Fond memories of bread boarding . . .

KZ

[Zimmerman]

The Wheatstone is over kill for this application, I mention it for fun only.

More of a question to me is where and how to mount the thermistor - inmmerse in fluid, metal or expy may be necessary to get accurate measurements.

I'll bet there are generic tips on the Internet which could be adapted to scooters.

You may even find something automotive that could be used on the scoot as is . . . that's easier but not as fun as home brew experimentation.

KZ

[LoveMyKymco]

Bread boarding is fun unless you dont make a diagram first and after lol. This is the same thing that we did for Ford trucks in Australia, their oil pressure gauges were just dummy gauges unless you used a 12v zenner diode and a 2k 12v resistor I think was the size. Been ages.
Go to ebay and type this in,"Trail Tech TTO Radiator Hose Temperature Gauge" , you will find a ton of sender/gauge combos from Trail tech for near 40 bucks.

[Zimmerman]

LMK,

Are you from "down under" ?  As we call it here in the states.

Which is halarious as we live on a globe in space and 'up' is any ray extending from the center.
I guess it just depends on which way the map is hung where you live.
In Austriala do they hang the map with Antarctica on the top?

This is earth - things don't have to make sense, or so I've observed.

KZ

[Zimmerman]

Thanks for the suggestion LMK, here's a link:

http://www.trailtech.net/tto_temperature.html

[MotoRandy123]

 Well I was trying to use the stock sensor and just set up a meter. I found the automotive ones
are different values than the Kymco scooters but most sensors are sold by thread type not range
of resistance. Most add on meters use their own sensor.

 I'm trying to do this on the cheap. I need to know the "normal" values you might see in the
radiator. I'm guessing 80C is normal and 90C is hot? So maybe I'm looking to read 75 ohms
down to 25 ohms?

 On my car 160F is normal cool reading and 180 is normal hot reading so 70c to 90c should work.
That estimates to 90 ohms down to 40 ohms. The old BMW K75 has an add on gauge and they
also add another sensor. The ECU is tied to the stock sensor so might not like it if we change the
signal (with some bias current). We might find the ECU converts the signal into a voltage that
we can read, some experiments are in order!