# Defrost Not Kicking In



## snowwy66 (Nov 5, 2017)

The engine has nothing to do with the vents. 

The vents are controlled by electronics and some gears. Probably done through the Body Control Module.


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## boraz (Aug 29, 2013)

snowwy66 said:


> The engine has nothing to do with the vents.
> 
> The vents are controlled by electronics and some gears. Probably done through the Body Control Module.


the defrost wont work worth a darn without a/c


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## boraz (Aug 29, 2013)

LiveTrash said:


> I still can't get the forum search function to work, so not sure if there's already a topic on this, but anyway, here it goes.
> 
> I left work yesterday and remote started my car as I always do. I pulled out of the yard and got out to lock the gate. When I got back in, the windows were a bit fogged up and I could tell the air coming out of the defrost vent wasn't dry. It was fairly humid that day and could tell the air from the vent was also humid. I'm not a very technical guy when it comes to engines and their components, but I took a peek inside the engine and all the pulleys and belts, etc seemed to be moving and spinning as they should. Nothing seemed seized up or making any unusual noises.
> 
> ...


was a/c light on originally?


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## Ma v e n (Oct 8, 2018)

Yes it's most likely just a glitch. Really unlikely it's a problem that needs to be addressed. If you're concerned you'll need to get it scanned for DTCs, and see if there are any faults recorded, barring that course of action Is either A, forget about or 2, disconnect the battery for several minutes to do what people like to call a "global reset"


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## LiveTrash (May 24, 2015)

boraz said:


> was a/c light on originally?


No. Doesn't that come on automatically when defrost is on? I've never separately turned that on. I leave defrost on practically all winter and it always seems to dry the air and defrost/defog windows just fine. I was mainly curious about this one-time thing.


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## snowwy66 (Nov 5, 2017)

boraz said:


> the defrost wont work worth a darn without a/c


On the east coast maybe. No problems on the west. 

Last year my compressor was broke from end of fall till almost summer before it got replaced. We don't have defrost issues around this side of the country. 

the a/c light don't light up in defrost on the 2's.


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## revjpeterson (Oct 2, 2013)

My guess is you either had a false reading from the ambient temperature sensor (the A/C compressor only runs with the defrost if it's above 45F), or it was just a BCM glitch that failed to send the command to activate it.


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## snowwy66 (Nov 5, 2017)

Which reminds me. 

The a/c won't kick on in defrost. There's not enough pressure to kick it on and it needs to be at least 50 psi. 

When it's cold outside. The high pressure drops, specially when going down the road. 

You can monitor high pressure in the torque app.


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## Ma v e n (Oct 8, 2018)

Based on conditions the car will engage the AC when in defrost, regardless of time of year. Ambient temp is obviously taken into account but system pressure and the ability to dehumidify (so dew points and ambient humidity in car) is the system primary purpose and goal. Even with outside temp below freezing, a properly operating system will create and drop sufficient pressure across the system orifice. Low side pressure, specifically the gaseous pressure in the evaporator core is what provides the dehumidification.


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## snowwy66 (Nov 5, 2017)

With outside temps below freezing. The compressor won't kick on. 

I left my house this morning with 38 sunny degrees and no compressor. At 39 it kicked on. Pressure was high enough. It's now 45 degrees and cloudy. A/c kicks on but defrost still don't.


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## ChevyGuy (Dec 13, 2014)

LiveTrash said:


> I still can't get the forum search function to work,


You can use Google, just tack on "site:cruztalk.com" on the end of the string of keywords your looking for. That limits the results to this site.

For example "Defrost not working site:cruzetalk.com"


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## boraz (Aug 29, 2013)

snowwy66 said:


> With outside temps below freezing. The compressor won't kick on.
> 
> I left my house this morning with 38 sunny degrees and no compressor. At 39 it kicked on. Pressure was high enough. It's now 45 degrees and cloudy. A/c kicks on but defrost still don't.


-4f yesterday, defrost and ac on.


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## snowwy66 (Nov 5, 2017)

boraz said:


> -4f yesterday, defrost and ac on.


35 and sunshine. No compressor. According to torque app.


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