Dash coolant temp gage not working - Mercedes-Benz Forum
 
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post #1 of 9 Old 06-12-2013, 04:59 PM Thread Starter
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Question Dash coolant temp gage not working

Help!!! Changed out the sensor. Checked new sensor OK. Checked voltage on sensor reads about 5V or so -OK. Checked all fuses non found bad. Pulled out dash cluster. Checked wires seem OK. Bought new dash cluster thinking the gage in the cluster is bad. Installed new cluster still coolant temp gage no response. Checked voltage on left plug with green wire (facing dash cluster). Reading 5v?? as I recall when electric fan kicked on after running engine for a bit.
Lost now...what did I miss?
HELP!!!
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post #2 of 9 Old 06-13-2013, 04:35 AM
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Is your temp sensor a one wire or two wire connection? And a picture of the sensor fitted to the engine would jog my memory of your system.

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post #3 of 9 Old 06-14-2013, 04:26 PM Thread Starter
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It is a two wire system with 5V reading from one wire to the next. Sensor has 2 pins. Connector is 3 hole but only 2 pins are plugged. Thank you

Check and clean all the ground points (brown wires) inside the engine compartment. You know one wire has 5v now take a live to the other wire with a small bulb inbetween and see if the bulb lights, if it does the ground is ok.

You have the live and if you have the ground then the only thing left is the sensor. New or not is irrelevant.

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post #4 of 9 Old 06-15-2013, 10:25 AM
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I don't have the factory wiring diagrams for your specific car, so don't know for sure...

But it is common on many cars for there to be more than one coolant temperature sensor. Many times one for the engine computer and another for the dash temp gauge.

Perhaps you can check with an ohm meter to see if the wire going to the gauge also goes to the coolant temperature sensor (both ends disconnected).

If not, look around the engine for another coolant temperature sensor.
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post #5 of 9 Old 06-15-2013, 10:43 AM
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Originally Posted by Elektrische View Post
I don't have the factory wiring diagrams for your specific car, so don't know for sure...

But it is common on many cars for there to be more than one coolant temperature sensor. Many times one for the engine computer and another for the dash temp gauge.

Perhaps you can check with an ohm meter to see if the wire going to the gauge also goes to the coolant temperature sensor (both ends disconnected).

If not, look around the engine for another coolant temperature sensor.
See #2, and this is exactly why I asked him for a picture. I too think he may have the wrong sensor, the one he changed may be for the fans.

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post #6 of 9 Old 06-16-2013, 06:17 AM Thread Starter
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Thank you I guess I did change out the incorrect sensor. Order one and will take picture thank you for your patience with me.
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post #7 of 9 Old 06-16-2013, 06:18 AM
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is engine harness new?the temp sensor is next to the thermostat

99 s320 359hp with nitrous wet shot 125,cold air,modified grill,and hood for airflow,borla exhaust,no cats,denso plugs.
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post #8 of 9 Old 06-19-2013, 04:03 PM Thread Starter
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No harness is not new...did try to ground it out and needle on gauge did NOT move.
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post #9 of 9 Old 06-20-2013, 05:40 PM Thread Starter
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OK received and replaced sensor. Then checked fuse it was blown also. Strange was OK before. Anyway it is repaired and works again.
Moral of the story ...replace the correct sensor then recheck the fuse. Even if it looks good it may be bad.
Thank you for all your help on this. Any reading this please remember to always include what fixed the problem.
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