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1977_L63H_P27
Samba Member
Joined: January 17, 2006
Posts: 2345
Location: Bristol, Tennessee
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 Posted: Sat Oct 30, 2010 7:00 am Post subject: |
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| raygreenwood wrote: |
So you hooked the power directly to the grid...or through the switch?
It sounds like either the grid you made did not have enough resistance (what did your grids resistance read)...or there should have been a dropping resistor in the switch unit. Also.....at $30 for epoxy...it was probably conductive epoxy...which is worth $30...and adds to the resistance. Ray |
I hooked the power directly to the grid. But only after using my meter to check resistance thru my switch "0.0", and power coming to the rear of the bus "12.9v" (my battery was fully charged at 13.3v). I'm thinking the resistance is a product of the power being spread out over the eight conductors. For some reason, I believe, most of the end connections failed as soon as power was connected leaving only one or two to carry the load. They super heated and burned thru the glass. Burns on my counter top confirm that.
Anyway, I've since acquired a replacement glass. And, of course, the grid is oxidized into non-existance. It's only $40 for another grid and if I order it today...
Peace!
_________________
| busdaddy wrote: |
...and try a few chubby ones until you find one you like.
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1977 Westfalia P27 
you can't spell Volkswagen without SWAG
M-code Plate
Full Moon Bus Club |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21519
Location: Oklahoma City
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| Posted: Sat Oct 30, 2010 7:44 am Post subject: |
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[quote="1977_L63H_P27"]
| raygreenwood wrote: |
So you hooked the power directly to the grid...or through the switch?
I hooked the power directly to the grid. But only after using my meter to check resistance thru my switch "0.0", and power coming to the rear of the bus "12.9v" (my battery was fully charged at 13.3v). I'm thinking the resistance is a product of the power being spread out over the eight conductors. For some reason, I believe, most of the end connections failed as soon as power was connected leaving only one or two to carry the load. They super heated and burned thru the glass. Burns on my counter top confirm that.
Anyway, I've since acquired a replacement glass. And, of course, the grid is oxidized into non-existance. It's only $40 for another grid and if I order it today...
Peace! |
The question I really had was....what did the resistance of the grid that you measured?
This has been the problem with defroster grid kits for eons. Unlike printed grids...you are at the mercy of the joints on the grid lines. As grid lines detach for any particular reason...the resistance on the system drops.
It is much much smarter to install this type of grid in an endless loop (snake pattern) so if a gridline breaks it can never transfer the load. A break can be patched easily...and if a joint patch breaks...again...it will not fry the grid. Ray |
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1977_L63H_P27
Samba Member
Joined: January 17, 2006
Posts: 2345
Location: Bristol, Tennessee
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| Posted: Sat Oct 30, 2010 8:29 am Post subject: |
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[quote="raygreenwood"]
| 1977_L63H_P27 wrote: |
| raygreenwood wrote: |
So you hooked the power directly to the grid...or through the switch?
I hooked the power directly to the grid. But only after using my meter to check resistance thru my switch "0.0", and power coming to the rear of the bus "12.9v" (my battery was fully charged at 13.3v). I'm thinking the resistance is a product of the power being spread out over the eight conductors. For some reason, I believe, most of the end connections failed as soon as power was connected leaving only one or two to carry the load. They super heated and burned thru the glass. Burns on my counter top confirm that.
Anyway, I've since acquired a replacement glass. And, of course, the grid is oxidized into non-existance. It's only $40 for another grid and if I order it today...
Peace! |
The question I really had was....what did the resistance of the grid that you measured?
This has been the problem with defroster grid kits for eons. Unlike printed grids...you are at the mercy of the joints on the grid lines. As grid lines detach for any particular reason...the resistance on the system drops.
It is much much smarter to install this type of grid in an endless loop (snake pattern) so if a gridline breaks it can never transfer the load. A break can be patched easily...and if a joint patch breaks...again...it will not fry the grid. Ray |
I was getting 0 resistance across the grid as well. The way the Frost Fighter kit is supposed to go on has the top three lines connected to a short bus bar. They go across to a longer bus bar that connects them to the middle three. Which go back across to a another long bar that connects them to the last three. And then across to the last short bar. Power goes to one short bar and ground on the last. Exactly as you said, a break wouldn't cause catastrophic failure. One day I'll learn  . Peace!
_________________
| busdaddy wrote: |
...and try a few chubby ones until you find one you like.
|
1977 Westfalia P27
you can't spell Volkswagen without SWAG
M-code Plate
Full Moon Bus Club |
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