Junaid786

i took my car to my mechanic yesterday to get my temperature sensor replaced and i bought the sensor from NAPA auto parts which cost me like 10$ and it was green color. but when i went back to my mechanic to pick my car he said i had gotten the wrong sensor and he showed me the blue sensor in the front near the radiator. and now i've been doing my research before i took my car to my mechanic and every body been telling me that green is the updated one from blue for whatever reason. and supposably the sensor is located in the back so why would he show me the sensor in the front near the radiator? if its not the temperature sensor then wat sensor is it? and i guess the blue one i have now is wider from the sensor i bought so my question is? does the temperature sensor located in the back or the front? or could it be possible i have two temperature sensors? please help me im so confused. and just to let you know My temperature gauge is working fine it stays in the middle like it should.

acarney

I believe there are two. At least on my 2002 A6 2.7t there are two. The blue one at the bottom of the radiator on the hose that connects to the housing. Then there is on behind the engine on the passenger side. This one had a green sensor for me.

I'm not entirely sure which does what, but I'm pretty sure one is just reading the coolant temp for the gauge inside the car while the other is more important for actually making sure the car is maintaining the correct temp.

Junaid786

thanks alot i guess i have to buy the blue one now lol i dont why audi engineers makes things difficult im sure they could have just have one sensor for both function to control the gauge and to maintain the coolant temp. atleast now i know i wasn't going crazy lol

Airbag

doesnt one turn on the fans ? the one up front ?
the green one senses coolant temp for cold start enrichment. The only one i have ever changed is the one at the back .. it should have come with a new O-ring also.

Airbag

leads to other questions though ... how about more back story ? why did you take it to get your temp sensor replaced, and why did your mechanic tell you it was the one at the front .. i hate these half stories ..

acarney

Ya, I thought one was pretty basic (fans on or off) and the other (green rear one) dumped all the data that the ECU used for coolant temps.

I've only replaced the rear one too... Just replaced it now with a timing belt job and it was covered in oil and other crap while the blue one up front looked brand new (it's not).

Worldwidebeagle

There are three guarantees in life: death, taxes and VAG sensors die.

Replacing the front fan sensor brought my ac back to life. For a 2.7t, it was recommended to use a lower temp fan switch, from an old vanagon. Looks just like the old sensor but closes 10 degrees lower. Loads of threads on this. The regular places sell it, like autohasz, RM, Pelican. Now, the fan comes to cool down on for a few minutes every time I turn off the engine. Much better cool down that the stock fan sensor that only turns on when it's 95 degrees.

Junaid786

well the reason i took to my mechanic was because i have a CEL for it if the back one sends all the data to ECU then i dont know what is going on because my gauge works fine and im not sure why i have the CEL for it. maybe the front one is not working well since its also consider as Coolant temp sensor thats probably the reason im getting CEL. im not sure what the code is i forgot but i'll get the code and update more on it.

GTA_Driver

The green sensor in the back of the engine sends two signals. One for the ECU, and another to the dashboard. Just because the dashboard reads fine doesn't mean the sensor is fine.

In fact, a very common issue with a failing temp sensor is difficulty starting a car especially if you shut it down for 10 minutes and then try to start it.

jcman

The front sensor is for the rad fan control and do keep in mind that this sensor is for cars with an electric primary fan.