... my MY 99.5 took the blue
Difference between Blue and Green ECT
Thread Starter
New Member
Joined: Sep 2006
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Difference between Blue and Green ECT
97' A4 2.8 quatttro
I recently replaced the engine coolant temp sensor and the one I pulled out was blue an dth eone i got from local audi dealer was green. I didnt think much of it. What sucks is im still gettting the red blinking light inside dash and when i idle for extended period of time it will overheat. Any suggestions and what is the diff between Blue and Green ECT??
I recently replaced the engine coolant temp sensor and the one I pulled out was blue an dth eone i got from local audi dealer was green. I didnt think much of it. What sucks is im still gettting the red blinking light inside dash and when i idle for extended period of time it will overheat. Any suggestions and what is the diff between Blue and Green ECT??
Member
Joined: May 2005
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a comment....
The green version should be the coolant temp sensor located behind the head on the passenger side. The blue sensor is the coolant temp sensor for the fan, usually located in the lower hose but sometimes in the rad on earlier cars.
Former Vendor
Joined: Dec 2000
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From: San Diego, CA
Green is the newer one for newer cars
Blue is the older one for earlier 96-98 models.
Green replaced the black ones on later models.
059919501 = Blue
059919501A = Green.
I don't believe blue and green should be interchanged.
Green replaced the black ones on later models.
059919501 = Blue
059919501A = Green.
I don't believe blue and green should be interchanged.
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AudiWorld Super User
Joined: May 2002
Posts: 5,138
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From: Redmond WA
Temp sensor won't cause the car to overheat.
It might cause the gauge to be off.
When you say you are overheating are you talking about the gauge or is the car actually overheating?
Vag.com the car see what temp you are actually seeing. Did you change the thermostat or waterpump recently. My A4's started to have problems at 150,000 miles it was the fan clutch.
When you say you are overheating are you talking about the gauge or is the car actually overheating?
Vag.com the car see what temp you are actually seeing. Did you change the thermostat or waterpump recently. My A4's started to have problems at 150,000 miles it was the fan clutch.
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a response....
If the fan does not turn on , or temp gauge is faulty then there is a good chance it will overheat. The rads in these cars are not terribly robust to begin with, they need all the help they can get. The sensor also effects the fuel mixture which can have an effect on temps. VW/Audi history with making sensors is not a stellar one.
AudiWorld Super User
Joined: May 2002
Posts: 5,138
Likes: 4
From: Redmond WA
Maybe but
The sensor has four connections. 2 for the gauge and 2 for the ECU. Even though they are in the same package there is no electrical connection between the two functions.
Therefore gauge can misread but ECU temp signal is OK or vice versa.
The trick is to see if in Vag.com they should both read about the same (allowing some tolerance)
And yes ECU sensor errors can cause bad running. I my experience the sensors go open circuit causing the ECU to run over rich which doesn't cause overheat.
Therefore gauge can misread but ECU temp signal is OK or vice versa.
The trick is to see if in Vag.com they should both read about the same (allowing some tolerance)
And yes ECU sensor errors can cause bad running. I my experience the sensors go open circuit causing the ECU to run over rich which doesn't cause overheat.