Coolant Temperature Gauge Sensor Issue in M800 (Type 1)


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Hi,

I am having an issue with coolant temperature gauge sensor which I fitted recently to my type 1 M800. I had to use a aftermarket sensor because I couldn't find the genuine part here (Sri Lanka). [frustration] The gauge goes all the way to "H" after driving a while. At the moment the cooling system is working fine (Confirmed it from MASS). But I would like to know the following.

If there is a situation where you couldn't trust the sensor, is there a way to know whether the engine is not overheating and operating under proper temperature?

Are there any specifications of the sensor which we could measure to make sure the sensor is ok?

Thank you.
 
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Re: Coolant temperature gauge sensor issue in type 1 M800

Sorry I have not yet explored my car in this regard.
By the way, what exactly went wrong with the car that you changed the sensor?
Can you post a pic of the part you replaced & the new one you bought. Might help others too.
 
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Actually the temperature sensor I had previously broke off from the back side (It happens pretty easily). Since I couldn't find the genuine part I had to go for an after market one and it seems act pretty weirdly. Actually I understand there is no remedy for the gauge issue until I find the correct part. But I am curious about the ways we could make sure the engine is running under correct temperature until I resolve this issue.

Thank you very much.

Following is a picture of the new part. I am sorry I don't have the old part to get a picture of it but both are identical.
 

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Varun560061

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Usually in type 1 800 the sensor is located on the radiator as seen in ss80's car.

Does the fan turn on when the car is over heated ? May be the sensor has failed again since its not an MGP, why not order for it ?
 
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Here are pictures from my car engine bay.
carlast update 018.JPG

carlast update 025.JPG

What is the second thing? Varun what are these? I am yet to replace these in my car so no idea about them [;)]
 
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Hi,

I am having an issue with coolant temperature gauge sensor which I fitted recently to my type 1 M800. I had to use a aftermarket sensor because I couldn't find the genuine part here (Sri Lanka). [frustration] The gauge goes all the way to "H" after driving a while. At the moment the cooling system is working fine (Confirmed it from MASS). But I would like to know the following.

If there is a situation where you couldn't trust the sensor, is there a way to know whether the engine is not overheating and operating under proper temperature?

Are there any specifications of the sensor which we could measure to make sure the sensor is ok?

Thank you.
First check the Sensor. If you have a voltmeter (digital one will help ) you can easily check the basic things. Search on google on how to check Engine Coolant Temp Sensor and you will get lot of links and videos. This way, you can rule out the possibility of the faulty sensor. Then you can check for other electrical issues, if any. Also check the connectors properly.

Also, you mentioned its an after market one - but is it compatible with your car model ? Different sensors will have slightly different ratings. ( varyying resistance with different coolant temp).

Replacing with an original one seems to be the best option. If the availability is still in question - you can try a nasty method ( not recommended and only in case you have to do this) to ensure your engine is not overheating.
Run your engine for 10-15 mins to allow it to reach the normal operating condition. Then remove the sensor ( be very very careful ) and check the specs against the voltmeter. The standard specs - like resistance vs temp - you will get in the internet, if not the accurate one - you will get some idea.

If your sensor is fine and ECU is getting wrong signal - that may cause some issues too. ECU will try the algorithms based on over heated engine - afterall its a machine[:)]
 
Thread Starter #7
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Usually in type 1 800 the sensor is located on the radiator as seen in ss80's car.

Does the fan turn on when the car is over heated ? May be the sensor has failed again since its not an MGP, why not order for it ?
Varun, Thank you for your attention. My problem is with the other sensor that gives the signal to the temperature gauge in the instrument panel.


Here are pictures from my car engine bay.
View attachment 66570

View attachment 66571

What is the second thing? Varun what are these? I am yet to replace these in my car so no idea about them [;)]
I guess it's the reverse light sensor.


First check the Sensor. If you have a voltmeter (digital one will help ) you can easily check the basic things. Search on google on how to check Engine Coolant Temp Sensor and you will get lot of links and videos. This way, you can rule out the possibility of the faulty sensor. Then you can check for other electrical issues, if any. Also check the connectors properly.

Also, you mentioned its an after market one - but is it compatible with your car model ? Different sensors will have slightly different ratings. ( varyying resistance with different coolant temp).

Replacing with an original one seems to be the best option. If the availability is still in question - you can try a nasty method ( not recommended and only in case you have to do this) to ensure your engine is not overheating.
Run your engine for 10-15 mins to allow it to reach the normal operating condition. Then remove the sensor ( be very very careful ) and check the specs against the voltmeter. The standard specs - like resistance vs temp - you will get in the internet, if not the accurate one - you will get some idea.

If your sensor is fine and ECU is getting wrong signal - that may cause some issues too. ECU will try the algorithms based on over heated engine - afterall its a machine[:)]

Good idea. Do you know where I could get the specs? I guess they could be found in the service manual but I couldn't find the service manual related to electrical wiring in the internet. Thanks
 
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Good idea. Do you know where I could get the specs? I guess they could be found in the service manual but I couldn't find the service manual related to electrical wiring in the internet. Thanks
Can you check for any DTC codes ? Sometimes it gives the exact error (if some malfunction other than the sensor). Also, a real time scanner ( like bluetooth enabled OBDII scanner can provide the temperature information )

Here's a generic method ( although exact spec from the service manual would have been better )

You can check the resistance of the sensor to ground using an Ohm meter. The resistance of a normal sensor to ground will vary a little depending on the vehicle, but basically, if the temp of the engine is around 200 deg. F., the resistance will be about 200 Ohms. If the temperature is about 0 def. F., the resistance will be over 10,000 Ohms. With this test you should be able to tell if the resistance of the sensor matches the temperature of the engine. If it's not accurate according to your engine's temperature, then you probably have a bad sensor.

Also, after running the engine for 10-15 mins - stop the car and then unplugg the sensor ( be careful ). Check the gauge.If the reading does not drop, probably a bad circuit and not the sensor.
 
Thread Starter #9
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Can you check for any DTC codes ? Sometimes it gives the exact error (if some malfunction other than the sensor). Also, a real time scanner ( like bluetooth enabled OBDII scanner can provide the temperature information )

Here's a generic method ( although exact spec from the service manual would have been better )

You can check the resistance of the sensor to ground using an Ohm meter. The resistance of a normal sensor to ground will vary a little depending on the vehicle, but basically, if the temp of the engine is around 200 deg. F., the resistance will be about 200 Ohms. If the temperature is about 0 def. F., the resistance will be over 10,000 Ohms. With this test you should be able to tell if the resistance of the sensor matches the temperature of the engine. If it's not accurate according to your engine's temperature, then you probably have a bad sensor.

Also, after running the engine for 10-15 mins - stop the car and then unplugg the sensor ( be careful ). Check the gauge.If the reading does not drop, probably a bad circuit and not the sensor.
Thanks for the quick reply. My car is a carburetor model so no ECU. I'll check the resistance to find out whether sensor is good as you described. I'll have to wait till the weekend to try it out. Thanks again.
 
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