Testing the Coolant Temp Sensor

97B4TDi

Veteran Member
Joined
Feb 5, 2007
Location
Wisconsin
TDI
1997 B4 Passat, 2013 Jetta Sportwagen TDI
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!
 

dieseljunkie

Veteran Member
Joined
Dec 29, 2006
Location
New England USA
TDI
96 Passat TDI wagon
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.
 

97B4TDi

Veteran Member
Joined
Feb 5, 2007
Location
Wisconsin
TDI
1997 B4 Passat, 2013 Jetta Sportwagen TDI
Thanks!

I know one is close to the block.

Where is the other?
 

97B4TDi

Veteran Member
Joined
Feb 5, 2007
Location
Wisconsin
TDI
1997 B4 Passat, 2013 Jetta Sportwagen TDI
Alright, i'll check it out!

Thanks again for the help.
 

97B4TDi

Veteran Member
Joined
Feb 5, 2007
Location
Wisconsin
TDI
1997 B4 Passat, 2013 Jetta Sportwagen TDI
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.
 

mech644

Veteran Member
Joined
Feb 7, 2007
Location
Blue Hill, Maine
TDI
'00 Golf, '14 Touareg
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
 

dieseljunkie

Veteran Member
Joined
Dec 29, 2006
Location
New England USA
TDI
96 Passat TDI wagon
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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