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Ask Don 'Mo Lurch' Your Own Que...
Don 'Mo Lurch'
Don 'Mo Lurch', Auto Mech / Electronics
Category: Chevy
Satisfied Customers: 20963
Experience:  Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
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Rear Deicer not working.

Customer Question

Rear Deicer not working.
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
there is 12 volts across the two terminals
Customer: replied 1 year ago.
I see no breaks in the heating ribbons
Expert:  Don 'Mo Lurch' replied 1 year ago.

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sorry for the delay............
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Greetings...... “Hi, I’m Don (aka MOLurch) and I look forward to helping you!”
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For the Heating Element to work, you have to have Voltage + & Ground -
The BCM (body control module) provides a Ground signal to the Element Relay to activate the Relay
The Relay then provides Voltage + to the Grid / Heating Element
The Grid is Grounded to G410
G410 is located on the Right Rear Pillar
click Attachments below

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Customer: replied 1 year ago.
what are you saying? Check the ground?
Expert:  Don 'Mo Lurch' replied 1 year ago.

I provided you with the Schematics to check the complete circuit Ground - & Voltage +
You posted:
there is 12 volts across the two terminals

You have to have a Ground - at one terminal when the Relay is activated
Check Relay to see if it has Voltage + & Ground & if it activates.

Customer: replied 1 year ago.
Ground looks great. I cleaned it up anyway. Not sure if it's related, but drivers mirror does not heat either - passenger mirror does.
Expert:  Don 'Mo Lurch' replied 1 year ago.

you need to check Ground at the Grid, as the BCM controls the Relay which provides the Voltage
The BCM is cued from the Door Switches of the Rear Door / Liftgate
IF the BCM does not get a signal from the Switches in the rear, then the Relay will not come on
The Door Mirror Heat is also controlled via the BCM
Should be Voltage + on the ORANGE wire of the Door Module to the Mirror & Ground - on the BLACK wire

Expert:  Don 'Mo Lurch' replied 1 year ago.

here is diagram

click Attachment below

Customer: replied 1 year ago.
What do you mean at the grid?
Expert:  Don 'Mo Lurch' replied 1 year ago.

grid = De-icer film on the glass or what you called the heating ribbons