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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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 Posted: Sat Feb 08, 2014 5:31 pm Post subject: .2 volts through the rear defrost - improvement ideas? |
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My rear defrost has never worked. It never been an issue safety wise, but it has always bothered me that it doesn't work. Mirror heat fine. Switch is good. Fuse is good. Connections to the grid are good.
I get .2 volts in all places. At the wire, anywhere on the grid, and on the other side. So, I guess the good news is the grid is good.
Why would my voltage from the switched wire be so low? High resistance? Any suggestions?
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2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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| Posted: Sat Feb 08, 2014 5:41 pm Post subject: |
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measure the voltage drop across the switch (volts reading from the hot input wire at the switch, to the output wire on the switch, with the switch TURNED ON. if you see a big 12 volt or so drop, then the switch is bad. you should have about 12 volts when switched off however, if not (ie you get low to zero volts when switch is off) then you have a bad ground at the window, if and only if you determine that the hot input wire to the switch is being supplied with 12 volts. by testing voltage between the hot switch input wire and a known good ground.
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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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| Posted: Sat Feb 08, 2014 6:00 pm Post subject: |
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Thanks for the tip.
I've got 12v through the wires. Voltage drop through the switch drops it to the .2 volts I'm seeing. Guess the switch is bad!
Not sure how the mirrors still heat with a bad switch.
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50352
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| Posted: Sat Feb 08, 2014 7:29 pm Post subject: |
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| kirkvw72 wrote: |
Thanks for the tip.
I've got 12v through the wires. Voltage drop through the switch drops it to the .2 volts I'm seeing. Guess the switch is bad!
Not sure how the mirrors still heat with a bad switch. |
If you had 12.5 volts at the battery side of the switch and 0.2 V across the switch then you should be seeing 12.3 volts across the grid. What do you get when you read between the ground end of the grid and a good ground on the body? |
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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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| Posted: Sat Feb 08, 2014 7:33 pm Post subject: |
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The switch is definitely bad. Light works fine a through me off. Looks like someone tried and failed to fix it in the past. 12+ volts go in the switch, only .2 come out. I get .2 across the entire grid.
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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