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Discussion Starter #1
Since winter is coming I wanted to get my defrost working again. Last winter it did not seem to work well at all. I figured the window was not getting juice. Well it is. The strips are getting 12 volts, so in theory it should work. Is it possible for these windows to go bad even if they are getting the 12 volts? I just had my defrost on for ten minutes and the big strips where the wires plug in were still stone cold. I figured you could tell on those when they warm up. Am I right? Do those 2" wide strips at the base of the window warm to the touch? Also how would one test the whole thing without snow? I am sure the window itself will not get warm enough to feel.
 

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on mine, only the top half would defrost, i had really tiny tears inthe wire, that took awhile to find, maybe you do as well?
 

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Touching a grounded test light to the grid from the inside will show you if voltage is running through the window.On the small grids,the test light will dim as you go from left to right(could be right to left,i don't really remember,but you'll be able to tell),facing the back of the truck.You can go along each line to find any breaks in the grid,the test light won't light on the ground side of the break.They sell repair kits for fixing the window.Make sure the terminals aren't corroded or broken at the glass.
 

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Only the Bronco
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ok, now an even better question, can rear defrost be put into a 78-9 Bronco????
 

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I have no idea how the rear defrosts are on your broncos, but is there a ground contact switch anywhere on the tailgate? if it is, maybe it's not contacting like it should :shrug

i_alone, I seem to remember a rear defrost kit being sold thru JC whitney
 

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Discussion Starter #7
miesk5 said:
yo as Pwrs advised use a light or multimeter to test the grids as described and as shown here:
http://www.frostfighter.com/ff_troubleshoot.htm

This firm's def repair product is sold at almost all parts shops.
Well I appreciate the advice but like I said I have already tested the strips (grids) on the window. All but one are getting the 12volts. I supose then it should work but I have this feeling once the snow falls it will not melt off the way it should.
 

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BoulderBronco said:
Well I appreciate the advice but like I said I have already tested the strips (grids) on the window. All but one are getting the 12volts. I supose then it should work but I have this feeling once the snow falls it will not melt off the way it should.
I always thought it was a continuous circuit. I'd pull the tg access panel, and check for continuity between the two plugs that should feed the defrost (I'm going off memory here, havent' looked at it in a long time). Unless the grid will provide too much resistance for a multimeter to overcome?
 

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They only heat up to about 85 deg F.
When the rear defr. is on power is switched on to one side of the grid lines. The power then flows through each line, and out to a common ground connection on the other side of the window.
Terminals are soldered to two vertical conductors called bus bars on each side of the glass; one serving as the feed connection (battery voltage) and the other as the chassis ground.

When the circuit of any horizontal grid is interrupted, no current will flow and that particular grid will not heat up.

Connect the black lead from your MM to one of the vertical "bus bars" and the red lead to the other bus bar. With the meter set to measure DC volts, the display should indicate 10 to 14 volts; a lower reading indicates a loose ground wire.

With the black lead of the MM grounded, touch each grid wire at its midpoint with the red lead. A reading of approximately 6 volts identifies a grid with no opens. A reading of 0 volts indicates the current path is broken between the midpoint and the battery side of the grid.

A reading of 12 volts indicates that the circuit is open between the midpoint of the grid line and ground.
 

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ok, i only have three horizontal lines that get hot and melt snow :eek:
i want all of them to work, instead of buying a new window, can i find where they are broken and maybe solder on a patch?
 

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knarf121 said:
ok, i only have three horizontal lines that get hot and melt snow :eek:
i want all of them to work, instead of buying a new window, can i find where they are broken and maybe solder on a patch?
As people have noted most auto parts stores sell repair kits. Get yourself one of those and go to town.

Tim
 

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Discussion Starter #14
Well I still have a problem. I have done everything and it checks out fine. Every bar has 11.5V so it should work right. No. It still does not melt snow. Even a tiny bit. I can't figure this out. All bars are getting the power so the defrost should work but it doesn't. Can anyone help me out here? I am lost of what to do about it. :banghead
 
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