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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old November 16th, 2011, 07:41   #1
97B4TDi
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Default Testing the Coolant Temp Sensor

I've noticed a lot of threads on here going over CTS issues and couldnt find anthing about this so I was curious: Is there a way to test it to determine if it is faulty?

Thanks!
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Old November 16th, 2011, 08:02   #2
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If you have VCDS, check coolant temp and ambient temps when the car is dead cold and they should be close to each other. If you do not have VCDS, measure the resistance of both sensors. At any given temp, one should be close to double of the other. That's what I have observed on my sensor, which I believe to be good.
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Old November 16th, 2011, 08:19   #3
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Thanks!

I know one is close to the block.

Where is the other?
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Old November 16th, 2011, 08:39   #4
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It's on the plastic coolant flange on the head between cyls 3 and 4. It has 4 terminals, 2 per sensor.
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Old November 16th, 2011, 14:00   #5
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Alright, i'll check it out!

Thanks again for the help.
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Old November 17th, 2011, 07:52   #6
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Ok What pins go to what sensor?

Im asking this because the temp has been floating around 160-175 on my dash gauge rather than the normal ~190. I've noticed it for a while and may just benefit from replacing it and seeing where to go from there. The car I am referring to is in my signature and for a little history i have no clue if or when the thermostat was last replaced.
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Old November 19th, 2011, 07:17   #7
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I had a similar situation with my Golf, ALH vs AHU but systems function similarly. I replaced the temp sensor and the thermostat, problem all fixed. The 'stats have a reputation of becoming slow to respond over time and the sensors can be dodgy as well
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Old November 19th, 2011, 07:42   #8
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Quote:
Originally Posted by 97B4TDi View Post
Ok What pins go to what sensor?

Im asking this because the temp has been floating around 160-175 on my dash gauge rather than the normal ~190. I've noticed it for a while and may just benefit from replacing it and seeing where to go from there. The car I am referring to is in my signature and for a little history i have no clue if or when the thermostat was last replaced.
Search for a Digital Corpus's thread that I posted in. I think I posted which color wires is which sensor.
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