1973 heat/defrost light

[Fs71]

my 1973 heat/defrost light is extremely dim; so dim you can barely tell it is on. When I open it up and probe the interior with a test light ( if I hit the right spot ) the light becomes extremely bright. I am completing the ground with the test light. Any one have any ideas? How do I fix this?

Thanks

[Dougster43]

There is a resistor inside the case of the heat/defrost switch that is wired in series with the bulb on the positive lead. When you see it go bright you are applying power between the resistor and the bulb.

The fix for this would be to change to a resistor with a lower resistance value. As I recall, the stock resistor was 360 ohms. I know when I replaced the bulb I couldn’t even get the new bulb to light up. I tried several different resistors. For me, anything at 150 ohms or less made the bulb way too bright. I would have to verify but I think I wound up with either a 180 ohm or 220 ohm resistor to get the right brightness.

You would use a soldering iron to take out the old resistor and replace it with the new one.

Hope that helps.