Author Topic: Rear defroster 79 ta  (Read 1550 times)

james.dowling99@yahoo.com

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Rear defroster 79 ta
« on: February 28, 2024, 03:06:07 PM »
Hello,I have a question concerning the rear defroster.
I removed my rear window due to scratches,  a lot of them.
I found a better rear defogger glass. The defogger grid has continuity.
I read voltage.  But it doesn't seem to get warm. My old one worked. I do not want to pay for an installation if this glass isn't going to defrost. What am I doing wrong? I am using an infrared thermometer Don't notice a temperature change. Any insight appreciated.
79' Y84 WS6 {wife's}
73' Sedan Deville {Survivor}
75 Delta 88 conv {under construction}
12' Mazda 3I
18' Sierra

Wallington

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Re: Rear defroster 79 ta
« Reply #1 on: February 28, 2024, 09:08:39 PM »
You've tested both ends of the circuit to make sure power runs from wire to wire? The rear glass is basically like a giant fuse, live wire one end, ground wire the other and it heats up instead of blowing, based on the power input.

Did you only use a testlight or run some extension leads to test off car? One end for live power when turned on, the other end that normally ground near the parcel tray needs similar.

james.dowling99@yahoo.com

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Re: Rear defroster 79 ta
« Reply #2 on: February 28, 2024, 09:28:05 PM »
I first jumped it with battery, + to +, - to -. Then laid it in the car, connecting power and ground. It doesn't seem to heat up more than a few degrees. Did this w ignore on, and then with the car running. I Google what temp a defroster should reach, 85 deg is what I cam up with.  I'm getting mid 60s glass was upper 50's before powering up. Green light on Def sw is illuminated when I turn it on.


79' Y84 WS6 {wife's}
73' Sedan Deville {Survivor}
75 Delta 88 conv {under construction}
12' Mazda 3I
18' Sierra

jbanna

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Re: Rear defroster 79 ta
« Reply #3 on: March 15, 2024, 12:49:46 AM »
I replaced my rear window about 30 years ago, with a junkyard one, and it has worked great ever since; however, I did have to repair a couple of the grids with a kit readily available at auto parts stores - if you do it right and test the resistance on the "unbroken" grids, you should have the same results - there can be breaks not easily visible...
78 White T/A, Carmine interior, Fisher T-tops, WS-6 package, 3.08 gears, a/c, rear discs. Original 403 with 300,000 miles replaced by new Pontiac 455 (roller everything, 6x-4 heads, Performer manifold, Hooker Headers, Hughes converter, Cliff's Q-jet).

Re: Rear defroster 79 ta
« Reply #3 on: March 15, 2024, 12:49:46 AM »
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