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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | Joined: Mar 2009 Posts: 75 'Bolter | | 'Bolter Joined: Mar 2009 Posts: 75 | Hi, I just replaced my brake light switch (on the side of the master cylinder under the drivers side floor) with a new unit with screws in the ends of the two posts that stick out from the switch. My old unit has two posts but the end holes appear not to be threaded. Instead there are two holes going crosswise through the posts. Can anyone tell me what was the factory solution for attaching wires to the brake light switch? See photo of switch: https://goo.gl/photos/Ehg1d3XUyszUt7Ak7Thanks! Doug | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | The switch should be no, run heat to one side, other side to brake light circuit.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Feb 2000 Posts: 5,202 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,202 | Is there a tiny (allen head) set screw in the end of each post? | | | | | Joined: Mar 2009 Posts: 75 'Bolter | | 'Bolter Joined: Mar 2009 Posts: 75 | There is no noticeable threading in the holes and they do not go in very far (as would an Allen head slot). My other thought was that they could be threaded holes with broken off screws in them but the two holes are very similar in depth, something breaking off screw heads would probably not accomplish.
Thanks for the reply - Doug | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Get a 4-40 or whatever tap will fit, get appropriate set screws, Allen head would be appropriate, and go to town.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jul 2008 Posts: 1,321 'Bolter | | 'Bolter Joined: Jul 2008 Posts: 1,321 | Doug, To answer your question "How did GM wire the switch", to the best of my knowledge this SWITCH was used from 1936 - 1955. If you want to use the screw in type, buy a new one(less than $10). You will be better off with new anyway. Harold http://www.jegs.com/i/JEGS-Performance-Products/555/63070/10002/-1Check your local parts store, they probably have one in stock.
Last edited by Harold46; 05/03/2017 9:46 PM.
Harold
Is a restoration ever finished? | | | | | Joined: Feb 2011 Posts: 583 'Bolter | | 'Bolter Joined: Feb 2011 Posts: 583 | My 39 also had a pressure switch on the side of the master cylinder. Got tired of replacing it, so I put in a mechanical switch like the one Harold46 shows. Has worked fine for the last 15 years or so. There were already holes to mount the mechanical switch on the toe floor board.
Rick
1939 Chevrolet Stake Truck
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