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 Post subject: What the heck is this?
PostPosted: March 5, 2018, 2:50 pm 
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Joined: February 15, 2018, 8:32 pm
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Location: Vancouver, BC. Canada
Does anyone have any idea what the purpose of this circuit is?

There's a temperature sensor just downstream of where the cat-converter used to live in my exhaust system. It's wired to a 'module' located on my firewall next to the battery.

The module appears to be wired to a warning lamp just below my horn button. When the vehicle is first powered up (ignition on), the lamp illuminates. Once started, the lamp goes out in about 10-20 seconds (hot exhaust?).

What's the purpose of this circuit? It's not a O2 sensor...it's clearly a RTD type temperature sensor.

The vehicle is a factory built '91 Westfield with a Ford 1600 CVH engine.

Cheers,

T


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PostPosted: March 5, 2018, 2:58 pm 
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The voice of reason
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Joined: January 10, 2008, 4:47 pm
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Maybe it indicates if the cat converter is over heating? That might happen if the motor runs rich or a sparkplug stops working. I remember once a friend who was having some engine trouble his cat converter under the car was glowing red...

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PostPosted: March 5, 2018, 3:01 pm 
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horizenjob wrote:
Maybe it indicates if the cat converter is over heating? That might happen if the motor runs rich or a sparkplug stops working. I remember once a friend who was having some engine trouble his cat converter under the car was glowing red...


Actually, the light goes out once the exhaust warms up, suggesting that it might be there to detect a cold or plugged cat?


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PostPosted: March 5, 2018, 4:14 pm 
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"Yes inspector, of course it has an O2 sensor to ensure the cat is working properly....See?"

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PostPosted: March 5, 2018, 4:57 pm 
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OK, so it indicates correct or safe operating temp. If the light didn't go on when it was cold you wouldn't know the light worked. If the exhaust exiting the converter is not hot, the converter is not working yet. Modern ECUs run the engine rich until the converter gets up to temp, that helps it get hot sooner and start working sooner which helps pass the tests.

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PostPosted: March 5, 2018, 7:00 pm 
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horizenjob wrote:
OK, so it indicates correct or safe operating temp. If the light didn't go on when it was cold you wouldn't know the light worked. If the exhaust exiting the converter is not hot, the converter is not working yet. Modern ECUs run the engine rich until the converter gets up to temp, that helps it get hot sooner and start working sooner which helps pass the tests.



Perhaps......but even when the car had its Cat in place, the light would turn off within 10-seconds. Do converters typically warm up that quickly?

Given that the car is fitted with Webers, I don't see any facility to enrichen the carbs during warmup...is that even possible?


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PostPosted: March 5, 2018, 7:01 pm 
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Driven5 wrote:
"Yes inspector, of course it has an O2 sensor to ensure the cat is working properly....See?"


I think you're right! This car was built for the Japanese market...perhaps they needed to see an "emmissions" warning lamp to meet import requirements?


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