Is a Nason switch adjustable?

[windsorbill06]

My nason switch at the parking brake plunger has been intermittent.  I had a new spare switch so I swapped it out and seems to have solved the issue.  The old one isn't that old, maybe a few years.

I took the old one apart on the bench and it's pretty simple.  Depending on how tight you screw down the cap, seems to be how much air pressure is needed to make the connection.   With my meter connected to the bed and black wire, I can tell when the switch does activate when I add air pressure while on the bench.  There was no debris or corrosion when I took the switch apart.

My question is has anyone adjusted the switch and keep it as a reliable spare?  When I bench tested it, the air I was using was not a controlled pressure but I consistently closed the contacts every time air was applied.
 

[Speerfamily]

Definitely interested in the answer to this question.  My Nason switch even after replacing is a constant pain.. have to push it in and out a couple times to get the parking light to come on now.

[gburgman2000]

https://www.irv2.com/forums/f115/my-thoughts-on-the-nason-parking-brake-switch-197560-3.html

 

Bob details how to build your own in a PDF in post #32

[windsorbill06]

Thanks.  I did see that before I posted this and it's informative.  I can't even imagine me ever getting close to the 1M cycles in my lifetime.  And as Bob said, that is misleading too. 

 

Since you can screw the cap on and lower/raise the black plunger housing inside the switch, I was wondering if anyone had just done some sort of 'calibrating' to the adjustable part.  I don't know if Nason did it that way or not.  I know I can put the cap on tighter that it was originally, and keep the switch closed all the time.

Edited October 22, 2020 by windsorbill06

[Bob Nodine]

Since I wrote that document the pressure switch has become obsolete. Someone pointed this out to me and found a good substitute that has a fixed actuation pressure of 70 PSI. I updated the document with this information on the first page. Here is a PDF of the updated document.

 (update Dec 2019) A close look at the Nason parking brake switch.pdf

[Frank McElroy]

Bob - Thanks for the update.  FYI - Last December I updated the downloads (files) with the updated version.

 

[ready2retire59]

I recently assembled and installed Bob Nodine's Nason park brake switch replacement.  Everything works perfectly.  All the parts were readily available.  Even the weatherpack 3 pin connector was available on Amazon in a 5 set package for about $13.00.  The weatherpack can be used if you do not want to use the connector from the old Nason switch.  I was able to tap into the 12v and ground lines feeding the switches for the hydraulic levelers for my power source to the relay.  My hardest part of the job was re-supporting the park brake actuator because the plastic console was cracked.  I used a small steel right angle bracket cut to fit and mounted between the plastic and the actuator.  It supports the actuator and can't be seen.    

Thank you Bob.  Your design with the single contact pressure switch should last the life of the motorhome. 

Tony Chiulli

'03 Windsor, '05 Ram pickup