01 S8 temp gauge problem
10-25-2004, 11:54 AM
#1
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01 S8 temp gauge problem
I noticed that the temp gauge is not always working. It sometimes stays all the way down at cold when I know the car is warmed up. Is this a bad sending unit or something? Also, does the fuel injection or anything else rely on this temp reading to adjust fuel mixture, etc...?
10-25-2004, 12:32 PM
#2
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You need to vag-com it
Yes, the fuel injection looks at this signal....if you vag-com it, it will tell you the temp of the engine, and if it also shows low, then you know it's the sensor.
If it shows normal temp, then you know it's either a bad connection to the instrument cluster or a bad gage.
pw
If it shows normal temp, then you know it's either a bad connection to the instrument cluster or a bad gage.
pw
10-25-2004, 04:14 PM
#3
Checking and changing the coolant temperature sender
At least on the 4.2 5V, the fuel injection and gauge use different sensor elements in the same sensor. In other words, the sensor has four wires, two for the instrument cluster, and two for the engine computer. The climate control receives a coolant temperature reading from the instrument cluster via CAN-BUS.
You can use VAG-COM to check the instrument cluster's view of the temperature, or you can read it directly on the climate control display, clicking the driver's up arrow button while holding the recirculation button. Then push driver's + until the left display shows 102. The right display will show the coolant temperature in degrees C as seen by the instrument cluster.
This will probably let you rule out the gauge mechanism and go buy a sensor and O-ring for $9 from the dealer. (I'd be willing to pay $12 for one that doesn't break...) Remove the central engine cover and air intake pipe, and if it's like the A8 4.2 engine, the sensor will be a green thing mostly hidden under a four wire plug in a transverse coolant pipe near the top back of the engine, closer to the right side. Wet the new sensor's O-ring with coolant, depress the electrical connector's catch from the top to unlatch it, unplug it, slide out the plastic retaining clip (there may be a wiring harness to move out of the way), wiggle the old sensor out, push the new one in, reclip, plug in, and top up the 100 ml of coolant that escaped. I did it last weekend, and it fixed a gauge problem with symptoms like yours.
Tom
You can use VAG-COM to check the instrument cluster's view of the temperature, or you can read it directly on the climate control display, clicking the driver's up arrow button while holding the recirculation button. Then push driver's + until the left display shows 102. The right display will show the coolant temperature in degrees C as seen by the instrument cluster.
This will probably let you rule out the gauge mechanism and go buy a sensor and O-ring for $9 from the dealer. (I'd be willing to pay $12 for one that doesn't break...) Remove the central engine cover and air intake pipe, and if it's like the A8 4.2 engine, the sensor will be a green thing mostly hidden under a four wire plug in a transverse coolant pipe near the top back of the engine, closer to the right side. Wet the new sensor's O-ring with coolant, depress the electrical connector's catch from the top to unlatch it, unplug it, slide out the plastic retaining clip (there may be a wiring harness to move out of the way), wiggle the old sensor out, push the new one in, reclip, plug in, and top up the 100 ml of coolant that escaped. I did it last weekend, and it fixed a gauge problem with symptoms like yours.
Tom
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