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Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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I have a 2000 New VW Beetle. The BLUE temperature light on ...

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I have a 2000 New VW Beetle. The BLUE temperature light on the cluster stays on for an extreme amount of time and sometimes does not even go out at all on drive home from work.(approx. 20 kms) Also the check engine light shows a code for rich mixture.(as far as I remember it was P0172) My question is .. Is it as simple as replacing the engine coolant temp. sensor?? 2000 2.0l New Beetle.Customer

Good morning!

An engine coolant temp sensor is one possibility, but a far more common failure would be an engine thermostat that is out of calibration (opening too soon resulting in a colder than normal engine temperature).

The computer is responding normally to a cold engine temperature by richening fuel mixture, since it "thinks" the engine is still warming up untill it reaches it's designed 195 degree F operating temperature.

Check your engine's actual operating temp using a non-contact thermometer, or try installing a new thermostat; this will likely resolve all of the issues you are experiencing.

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Customer: replied 9 years ago.
Yesterday I put a scanner on it and the coolant temp. sensor was reeding 30deg C. or about 80 F. Witch seems normal. (not yet fully warmed up)(I should have let it run longer but I was at work)But when I drove it home the blue light stayed on all the way home.In theory a thermostat sounds like the proper solution,as you know all models have common problems.Im under the impression that the VW has common defects with the temp. sensor.Is that correct,or do you believe that the thermostat is more the probable cause? Mike

Normal operating temperature for this engine is 195 degrees; if it is only reaching 180 degrees it is not up to normal temperature and will run rich. This is not normal. I do not know the exact temperature at which the blue indicator is turned off, but if you are only getting to 180F there is a problem somewhere. It could either be the thermostat or the coolant temp sensor (since that is where youa re getting the scanner reading).

You can confirm which part is causing the problem by taking a manual engine temperature reading with a temp gun. I can tell you from experience that I have never had to replace a CTS on a VW beetle, but ahve had several failed thermostats over the years.

A good rule is to always start with the simple, obvious stuff before trying anything less likely or more complicated! <smile>

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