View Full Version : Oil temp and Voltage guages faulty readings?

12-08-2010, 03:16 PM
Hey there!

So I've been watching my oil temp and voltage guages for a while, and everything in my car works perfect however the guages seem to be doing something weird...they both seem to be off of ideal readings by the same amount and opposite. I'm not sure if this is a fuse thing or if the guages are faulty.

The pictures will explain this better, 99.5 1.8T quattro:





Like I said before, everything works fine and I have no problems or CEL or warning lights of the sort. They start off at their respective minimums, and after start up the voltage guages sits where it is in the picture and fluctuates minimally if I put my defroster, wipers, etc. on - normal drain. As for the oil temp, it starts at minimum and then as the car warms up it just sits at the point in the picture, it does not move after that. Every other guage works normally...I only have the issues with these two, they haven't caused any problems, I just want to know why they aren't reading properly. It just annoys me when I look down and see them reading wrong.

Any suggestions are apprectiated! Thanks in advance!


12-08-2010, 03:28 PM
Oh I forgot to mention that when I got my timing belt done in August, the temp sensor and thermostat were replaced along with the waterpump and all. It was the same before and after the new sensor.... :(

12-08-2010, 04:58 PM
Everything looks great there.

Operating temp for the oil on a 1.8T is between 180F and 200F normally. So between 82C and 93C. From the looks of your gauge it appears to riding right around 90C, which is perfect. As for the voltage, that is pretty good voltage at idle. The regulator should hold it around 14 volts or so, but at idle with some accessories on, a bit lower is acceptable. Yours is at 13 volts, so that is perfect.

On my 1.8T with the high beams, seat heaters, rear defroster, and blower on full, the voltage will drop as low as 12 at idle. It comes right up to 14 when I rev it up, though. Which is normal.

Nothing to worry about, everything looks great.

12-08-2010, 05:00 PM
same thing happens to mine. im pretty sure its normal.

12-08-2010, 05:05 PM
well if you have a DVOM you can easily tell how much volts, and go from there

12-08-2010, 05:06 PM
+1 here

12-08-2010, 05:15 PM
Oh perfect! Thanks a lot guys! I was worried I might have to replace the gauges or sensors.


12-08-2010, 05:19 PM
Oh perfect! Thanks a lot guys! I was worried I might have to replace the gauges or sensors.


I really like Volcano Black B5's like mine!

If your coolant temperature is acting a little crazy (ie randomly moving from the middle to the bottom) its gonna be your coolant temperature sensor.

12-09-2010, 01:33 PM
I really like Volcano Black B5's like mine!