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HI, I have a 2014 volt. I have notice twice this winter that ERDTT now shuts down by itself during a single trip after temperature rises over set point. I mean without shutting off the car to reset. It was not like that last winter, after being on, it stays on whatever the temperature change.
Did any one else notice that?
I never came back to the dealer since I take delivery in November 2013. Could Chevy make software update through OnStar?
Thanks
 

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Interesting. I have a 2013 and haven't had an instance that would demonstrate this behavior so far this winter, so I can't comment on that.

Did you notice what the temperature threshold was for ERDTT to turn off. I.e., is it only 1 degree above the ERDTT threshold, or something higher?
 

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In both cases, the set point was -10C (very cold) and it went off at -9C or maybe -8C but not higher then that. One C is about equal to 2F.
 

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The ERDTT starts when the ICE cooling liquid (antigel) temp goes below a set temp (from testing it is about 48 C/118 F) and it is stopped when it reaches another set temp (from testing it is about 63 C/145 F). These temps were obteined on a 2012 Volt by one of this forum users, Dominique Matte. In my Volt, ERDTT always cycles when temps below -10 C / 14 F.
 

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I know ERDTT cycles on and off when on. When I say I went off after temperature rises above set point, I mean it does not cycles anymore. It my case it went off for the remaining of the trip (about 15 minutes) after cycling on and off every 2-3 minutes.
 

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I have noticed this last year in my 2013, not so much this year because of a little resister, but I have seen this behavior before.
 

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The ERDTT starts when the ICE cooling liquid (antigel) temp goes below a set temp (from testing it is about 48 C/118 F)
To be clear, ERDTT is triggered by the ambient air sensor mounted in the bumper air intake louvers. When the outside air temp hit's the set point, ERDTT is triggered. Modifying this sensor with a resistor can lower the set point to prevent ERDTT until far lower outside temps are reached.

You are correct that the ICE then shuts down when the ICE antifreeze coolant hits a certain temperature (let's agree on your 48°C/118°F, though I'm not sure on the numbers).

But you make a good point about once ERDTT is triggered, the coolant sensor takes over—as long as the ambient air sensor remains at it's set point or lower. If the outside temperature warms above the ambient air sensor set point, the coolant temperature is ignored, even if it's below 48°C/118°F (or whatever the numbers are).
 

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The ERDTT starts when the ICE cooling liquid (antigel) temp goes below a set temp (from testing it is about 48 C/118 F) and it is stopped when it reaches another set temp (from testing it is about 63 C/145 F). These temps were obteined on a 2012 Volt by one of this forum users, Dominique Matte. In my Volt, ERDTT always cycles when temps below -10 C / 14 F.
I brought my Volt into the garage while I was working on Bluetooth pairing and I was surprised to see the engine start when I turned on the car. The ambient temperature was about 35F, well above 14F and the battery was fully charged.

Was this a way to heat the car or what?

Usually, neither my Volt nor my wife's Lexus hybrid run the engine when you are not moving.
 

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To be clear, ERDTT is triggered by the ambient air sensor mounted in the bumper air intake louvers. When the outside air temp hit's the set point, ERDTT is triggered. Modifying this sensor with a resistor can lower the set point to prevent ERDTT until far lower outside temps are reached.

You are correct that the ICE then shuts down when the ICE antifreeze coolant hits a certain temperature (let's agree on your 48°C/118°F, though I'm not sure on the numbers).

But you make a good point about once ERDTT is triggered, the coolant sensor takes over—as long as the AAT sensor remains at it's set point or lower. If the outside temperature warms above the ambient air sensor set point, the coolant temperature is ignored, even if it's below 48°C/118°F (or whatever the numbers are).
This is 100% correct. The Ambient Air Temperature (AAT) is used to trigger ERDTT (typically 25F/-4C in 2011-12 models) and once it does then the Engine Coolant Temperature (ECT) is used to control ICE run cycling in order to maintain coolant temperature in the cabin heating/engine cooling loop to be between 104F/40C and 150F/65C. (assuming AAT stays below the predetermined threshold)

To the OP, those "ICE cycling" bogies have not changed and have been in place since start of production (not something a software revision has affected) so you must have just "missed it" in the past.

WopOnTour
 

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Last winter we had very few days that flirted with the 26F set point on my 2011 so I experienced very few trips with temp rise to disable ERDTT. AAT sensor will update temp after 5mins at 15-25mph, down to a minute if moving 40 or above. Once updated it will refresh every 2 seconds. Also the reading will update IF the ambient temp has DROPPED since ignition was turned off.
 
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