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Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch
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56D500boy
Posted 2019-08-17 9:43 PM (#586151)
Subject: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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Last week sometime, I discovered that my NOS (three year old to me but less than 1000 miles) brake light pressure switch had failed. Rather than pursue another NOS switch, I decided to go with a new aftermarket two pin switch. The catch is the new ones are 1/8" NPT and the old one (at least on my car in my new Raybestos MC) was a 1/4" NPT switch. This required finding and buying a reducer bushing.

You would think that finding such a bushing would be easy but not in the automotive stores that I tried. Ended up finding one in the plumbing section of my local RONA building supplies store (owned by Lowes) in the plumbing section. Brass 1/4" MIP x 1/8" FIP perfect (after about 3 hours of frustration looking for one).

Installed it this afternoon while waiting for my garage construction contractor. Used male and female plug connectors on the new switch harness plug so I didn't have to change the OE wiring (except fix one or two problems (that had not caused the failure)).

Went quite smoothly. I finished with taping the connections and covering the new modified OE/New harness with some of that cheap corrugated wiring cover for now (I have better stuff - just couldn't find it today).

One of the benefits for me was now the "hot" red wire and terminal is now covered and protected from inadvertent contact with metal tools (Don't ask )

Here are the photos from today, starting with the OE switch (yes I know the white wire looks broken but that was NOT the problem):



Edited by 56D500boy 2019-08-17 9:47 PM




(56DodgeBrakeLightSwitch_FailedInternally.jpg)



(56DodgeBrakeLightSwitch_OEWithLargeNPT_SmallNPT_AfterMarketSmallNPT_withAdapterBushingAndWiringBits.jpg)



(56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchInitialInstall.jpg)



(56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchFinalInstall_1.jpg)



(56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchFinalInstall_2.jpg)



Attachments
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Attachments 56DodgeBrakeLightSwitch_FailedInternally.jpg (162KB - 365 downloads)
Attachments 56DodgeBrakeLightSwitch_OEWithLargeNPT_SmallNPT_AfterMarketSmallNPT_withAdapterBushingAndWiringBits.jpg (147KB - 391 downloads)
Attachments 56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchInitialInstall.jpg (219KB - 354 downloads)
Attachments 56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchFinalInstall_1.jpg (205KB - 353 downloads)
Attachments 56DodgeBrakeLightSwitch_WithAdapterBushingAndNewSmallNPTAfterMarketSwitchFinalInstall_2.jpg (151KB - 350 downloads)
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mobileparts
Posted 2019-08-18 1:46 AM (#586164 - in reply to #586151)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch


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Or -- for you -- or anyone else that doesn't want to be bothered with all of that
--- I have the N.O.S. (SLS29 Standard --- yes, very obsolete by all companies)
1955 - 1961 Chryslers, Dodge, DeSoto, and Plymouth stop light / brake
light switches.....
Always best to simply call me -- Craig -- 516 - 485 - 1935.....
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1960fury
Posted 2019-08-18 6:20 AM (#586170 - in reply to #586151)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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Actually you can find new 1/8" NPT brake switches everywhere. IMO a mechanical switch is the way to go, much more reliable, less cables in the engine compartment and you can adjust them too.
I like your threads about improving things, but that plastic connector and cable looks totaly out of place in a 56 Dodge engine bay.

Edited by 1960fury 2019-08-18 6:22 AM
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56D500boy
Posted 2019-08-18 11:19 AM (#586180 - in reply to #586170)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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1960fury - 2019-08-18 3:20 AM
Actually you can find new 1/8" NPT brake switches everywhere. IMO a mechanical switch is the way to go, much more reliable, less cables in the engine compartment and you can adjust them too.
I like your threads about improving things, but that plastic connector and cable looks totaly out of place in a 56 Dodge engine bay.


Sid: I think that going to a 1/8" NPT brake switch because they can be found everywhere is a good thing. If I had had a 1/4" NPT switch on my spares shelf I would have installed that but I didn't (I didn't think that I would need a spare switch for one with only 1000 miles on it and running DOT 3 brake fluid). I might have got another 1/4" one from my local NOS parts guy but I wasn't in the mood to drive there so I got what I got.

I can't disagree about the plastic connector etc. I hate that plastic wire tubing but I couldn't find my "snakeskin" mesh tubing yesterday. As for the connector, it might not be OE but it is definitely better than an exposed hot 12V wire the way the factory did it.

Probably all moot because I will be installing a Raybestos MC36221 (CARDONE 131323M ) drum drum dual master cylinder in my car anyway and it is NOT plumbed for a pressure switch so I will have to go to a mechanical switch. I could have gone that way now but it would take more time than installing the 1/8" NPT switch and I wanted to get back on the road.

My dual MC (which is currently hiding somewhere in the basement or garage):



Similar MC showing "switch" end (but no port):



Edited by 56D500boy 2019-08-18 11:22 AM




(OuterEndOfRaybestosDrumDrumMCNoPressureSwitchPort.jpg)



Attachments
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Attachments OuterEndOfRaybestosDrumDrumMCNoPressureSwitchPort.jpg (29KB - 355 downloads)
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1960fury
Posted 2019-08-18 12:57 PM (#586188 - in reply to #586180)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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56D500boy - 2019-08-18 11:19 AM

1960fury - 2019-08-18 3:20 AM
Actually you can find new 1/8" NPT brake switches everywhere. IMO a mechanical switch is the way to go, much more reliable, less cables in the engine compartment and you can adjust them too.
I like your threads about improving things, but that plastic connector and cable looks totaly out of place in a 56 Dodge engine bay.


Sid: I think that going to a 1/8" NPT brake switch because they can be found everywhere is a good thing. If I had had a 1/4" NPT switch on my spares shelf I would have installed that but I didn't (I didn't think that I would need a spare switch for one with only 1000 miles on it and running DOT 3 brake fluid). I might have got another 1/4" one from my local NOS parts guy but I wasn't in the mood to drive there so I got what I got.




Sorry, tipo, meant 1/4"
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71charger_fan
Posted 2019-08-24 10:43 PM (#586526 - in reply to #586151)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch


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When you make your new lines, just plumb in a 3/16" tee with a 1/8 NPT port. Dune buggy suppliers stock them. I got mine from appletreeauto.com
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71charger_fan
Posted 2019-08-28 9:30 AM (#586693 - in reply to #586526)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch


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Here's my dual MC with my 3/16 tee and 1/8 NPT switch from appletreeauto

Edited by 71charger_fan 2019-08-28 9:35 AM




(Plaza MC (2).jpg)



Attachments
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Attachments Plaza MC (2).jpg (152KB - 381 downloads)
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56D500boy
Posted 2019-08-28 11:43 AM (#586702 - in reply to #586693)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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71charger_fan - 2019-08-28 6:30 AM

Here's my dual MC with my 3/16 tee and 1/8 NPT switch from appletreeauto


I would be interested in learning more about all the tees and what nots you used to install that MC.

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71charger_fan
Posted 2019-08-28 5:30 PM (#586715 - in reply to #586702)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch


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As I'm disc/drum, I used an AAR 'cuda proportioning/metering valve. http://therammaninc.com/products/shop_list/Proportioning-Valves-200
Mounting the MC is on the third page of my thread about my '55 wagon http://www.forwardlook.net/forums/forums/thread-view.asp?tid=63722&...
This is the tee I used for the brake light switch https://www.appletreeauto.com/TEE-FOR-BRAKE-LIGHT-SWITCH-889-F/

Edited by 71charger_fan 2019-08-28 5:34 PM
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56D500boy
Posted 2019-08-28 5:55 PM (#586716 - in reply to #586715)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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Thanks for the details Terrance. Much appreciated.



Edited by 56D500boy 2019-08-28 5:56 PM
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71charger_fan
Posted 2019-08-28 7:53 PM (#586718 - in reply to #586151)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch


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Location: Frederick, MD
Inline Tube lists the 3/16 tee with 1/8 NPT https://www.inlinetube.com/products/te03
Oddly, they also sell them through their Ebay store for about 50% more.
Jegs sells a tee in their brake light switch kit https://www.amazon.com/JEGS-63070K1-Brake-Light-Switch/dp/B007WWSU1K...
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56D500boy
Posted 2021-01-29 2:27 AM (#608307 - in reply to #586151)
Subject: RE: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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.
Not for the first time, my new "temporary/tide-me-over" pressure brake light switch caused me hate my 56 Dodge.

I don't know if you followed my recent threads on this forum but if you haven't, I've been busy, figuring out and solving why my signal lights stopped working and why my horn is working inconsistently. I had those all sorted out by on Monday and then I started tidying up the wiring under the steering column (including the new LED (I love) eBrake warning light). I got finished (I thought) Tuesday, just after lunch.

I was about to take the car out for a spin when I noticed that all of a sudden, I don't have brake lights. WHAAAATTTT!!!??? ()

So my immediate thought was "I guess that I must have done something when I was doing the tidying up". I will have to un-tidy everything until I figure it out. ARRGGGHH!!

Oh well. Wasn't as if I was going on a trip or anything important.

The good news was the signal lights work great (again) and my horn is working very well. :P

Today (Thursday) I procrastinated all day (after taking a break yesterday) and finally went out to the garage (after having the heat on for 4 hours to get it up to about 18 C). Popped the hood. Removed the new brake light switch connector that I installed awhile back. Checked for 12V at the red wire (always hot, no key required). Yup. Put the connector back on. Opened the car door. Sat there for a moment figuring out the next step in tracing the issue. Stepped hard on the brake and saw the red LED brake light reflect off the inside of the closed garage door. WHAATTTT??!!!

Done. No issues. Probably just the connector. Now that I think of it, that is not the first time that I had that (connector) problem

It will be good when I install my new brake pedal and booster and I add mechanical brake light switch to the pedal.

This was the problem two pin, slide on connector:



Edited by 56D500boy 2021-01-29 2:30 AM
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wizard
Posted 2021-01-29 4:44 PM (#608344 - in reply to #586151)
Subject: Re: Replacing a 1/4" NPT two-pin brake light pressure switch with a newer 1/8" NPT switch



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Dave, it might well be bad contact where you spliced in the new wires. The old wires often has a lot of verdigris around the individual copper parts.
This might cause a good reading when you measure the tension, like 12 ish volts. However as soon as you have a consumption in amps (yes, even as low as the LED's consume), then you might have a bad lead with the result of no brake lights.

When I splice old car wires, I strip off the insulation and let the wire take a bath in citrus acid (1:10) and hot water. This will remove all verdigris almost immediately and then I always solder the splice.

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