# Odd - rear window defroster and climate control fan



## k_ob1991 (Apr 28, 2014)

Hello, I have a few questions that I hope you can help with. I have a 2014 Chevy cruze diesel. Love the car, love the power, love the mpg. I have noticed some odd things, and maybe that is just the way they are, but figured I would ask here. The first thing is the rear window defrost only clears the frost from the window in the area between the back seat heads rests....it clears that area really well, but the outside 10 inches on either side of the window only has lines defrosted through it.

The other odd thing is that when I have the the car on front window defrost, and the dials turned to full heat and full fan, I notice that the fan changes speed depending whether i am on the throttle or off. This happens mostly when the car is cold. The temp has been around 15 F here for the last couple of weeks. Let me know your thoughts. Just seems as though the electrical system does not have enough power.....Thanks in advance for your help.


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## jblackburn (Apr 14, 2012)

Last one makes sense - full fan draws a heavy amp load from the alternator. When the car drops back to idle, the alternator output decreases and the fan slows down a little bit. You don't notice it on the lower speeds.

Yeah, I noticed the other morning that my back window defrosts mostly in the middle and works its way to the outer edges before I got to it with the scraper.


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## 1877 iris ave (Sep 23, 2011)

our cars have a 140 amp alternator, thats huge. But there are many things that use electricity specific to our diesel cruzes---heated seats, fan, lights automatically on, def pump and heater, electric heater and, if I'm not mistaken, a fuel line heater. So when the engine is idling, especially when it's cold out, we can expect the voltage to be lower so naturally the heater fan will slow down a little.


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## bigluke (Aug 18, 2013)

Also lowering the fan speed when it didn't reach it operational temp helps drag the heat out of the electric heater element to make it more efficient and when the operational temps are reached it does the same thing to keep the engine hot by lowering the fan speed and keeping engine temps as it can on -10F and lower.


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## Robby (Mar 1, 2013)

The rear defog is 'Zoned'.

It is designed, by actually having a resistance change along the length of each grid line, to apply more heat to a given section.
And, they are all designed to clear the center first and then work out to the sides.
Sometimes (because the switch is on a timer) you have to hit it a second time to get full clearing.....or fairly full clearing depending on the temperature difference between inside the car and the outside temperature.....heh heh.

Rob


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## k_ob1991 (Apr 28, 2014)

Thanks for all of the help. You guys are very knowledgeable, and have saved me a trip to the dealer. Thanks!


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