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Discussion Starter · #1 ·
Hi,
I have a dew questions regarding the function of the Coolant temp sensor (the blue one, not the black one that sends out info to the gauge).
1) What exactly is it"s role ?
2) When does it start/stop functionning in a normal loop ?
3) Are a) Loss of power, b) Decreased gas milleage (significantly) c) buckling
all symptoms ? If so, in whih magnitude ?
4) What are the consequences of running without the coolant temp sensor plugged in ?
BTW I did change mine, but these are only questions I had !
Have a great day !
J-F
 

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Re: Coolant temp sensor questions...easy again ! (JF)

The blue one. I'm not 100% on this, so double check...
1- activate rad fan, and cold start enrichment
2- probably a temp coil that completes the circuit at a given temp
3- I don't believe a,b, or c are symptoms of failure
4- overheating when stopped, slow starting when cold due to lack of fuel - this in turn will be a harsh number on your starter and battery..experienced enough of that one
 

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Discussion Starter · #3 ·
Re: Coolant temp sensor questions...easy again ! (Tornado Wolfie)

quote:[HR][/HR]3- I don't believe a,b, or c are symptoms of failure
[HR][/HR]​
That was my original assumption, but I changed my O2 sensor, and once the car warms up, I definitely gained power going uphill, and that fixed some buckling, misfiring and horrible milleage. However it soon started again, and when I unplugged the coolant temp sensor, my car stopped buckling....I have yet to see the difference for milleage since I changed it yesterday !


[Modified by JF, 8:14 AM 1-30-2003]
 

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Re: Coolant temp sensor questions...easy again ! (Tornado Wolfie)

Um, I don't think you're correct.
quote:[HR][/HR]1- activate rad fan, and cold start enrichment[HR][/HR]​
It's really for telling the computer what the temperature of the coolant is so it can adjust mixture accordingly. Also triggers cold starts which are a very rich condition.
quote:[HR][/HR]2- probably a temp coil that completes the circuit at a given temp[HR][/HR]​
Cold starts (very rich) ends shortly after cranking. Loop stops when the coolant temp sensor gives the computer a certain degree (resistance).

quote:[HR][/HR]3- I don't believe a,b, or c are symptoms of failure[HR][/HR]​
Not sure about bucking, but the other symptoms are definitely symptoms of a broken coolant temp sensor. When it breaks it keeps the resistance very high and the computer thinks the engine is never warming up. It keeps the mixture very rich, making the car slow and have terrible gas mileage.
quote:[HR][/HR]4- overheating when stopped, slow starting when cold due to lack of fuel - this in turn will be a harsh number on your starter and battery..experienced enough of that one
[HR][/HR]​
Actually the car should run fine when it's cold, although when the car starts to warm up the mixture won't change and it'll run badly.
I think you've confused the coolant temp sensor with the fan switch which IIRC is at the bottom of the radiator.
edit: Another thing to remember is that the O2 sensor controls mixture along with the blue coolant temp sensor. Their failure symtoms are almost identical. Bucking is usually a symtom of a vacuum leak.
edit2: To make this even more confusing the mixture is actually set by the air flow meter and is adjusted by readings from the coolant temp sensor and 02 sensor. Think this is confusing? It's the simplest of all non-fuel-distributor electronic FI setups.

[Modified by VW-BMW, 5:41 PM 1-30-2003]


[Modified by VW-BMW, 5:43 PM 1-30-2003]
 
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