Re: dashlights dimmer switch

Posted by HH56 on 2019/11/13 21:46:23
Good job on the tool.

I can't see what is happening behind the wiper but I suspect there may be an end of the rheostat wire connecting to the top right terminal. If there is then see if this might be the way it hooks up.

If no obvious wire connection to the terminal, if you can take another photo with the wiper in a midpoint position and one of the front side that shows the rivets and anything they might be attached to then we can figure it out.

From what I see I suspect there could be a corrosion build up in the switch. Later year dash rheostats which were mounted on the headlight switches had a fixed and movable plate which rubs against each other to make the connection. In your switch the fixed plate looks to be the thick metal under the wiper with a solid leg that appears to be extending to what I call the power in terminal. Corrosion builds up between that fixed plate and the movable contact area below the thin wiper and the increased resistance is enough to prevent the dash lights from illuminating.

Ross has had good results in cleaning later switches by pushing a tiny bit of valve grinding compound under the movable plate and the wiper over the rheostat wire and working the switch to get the plates and contact areas shiny clean. Once clean use some brake cleaner or contact cleaner to get rid of any left over valve grinding compound. Contact cleaner would be best because it leaves a film that kind of hinders corrosion from forming again as quickly. If you use brake cleaner try not to saturate any phenolic or plastic that can be damaged by the cleaner.

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