Front Axle Engagement Air Pressure Switch - Replacement

[Commander5993]

Replacing Front Axle Air Pressure Switch

Hey All,

I'm having a problem with my front axle light on the dash not working.

I tried my front axle engagement switch today, and the light did not come on. So I turned the engine off, and I could hear it engage when I moved the lever. But the light below the lever did not come on.

So after checking wires, changing the bulb etc. Connecting the light directly to a power source, it came on and lit up fine. I finally decided to remove the entire air shift switch assembly and take a closer look. After doing so, I took it in to the work bench, and removed the pressure switch that the light wire connects to. When I did, I found a bunch of gunk inside, so I cleaned all that out of the assembly. And I tried to clean out the pressure switch, but it is sealed.

I then tried to bench test the switch by connecting it to my air compressor, and then use a voltmeter to check for continuity. I tried several times, but got nothing.

So I need to get a new pressure switch, and I started looking on Eriks. However, after doing some searching, I'm not really finding the pressure switch for the front axle air shift engagement anywhere.

What I did find is a "brake light pressure switch" It looks almost exactly like this switch except for the terminals, which wouldn't be a problem as I can just change the wires to the correct terminals, as I already have the military connectors.

Here is a link to this "Brake" pressure switch:

Brake Light Air Operated Switch, M35/M54/M809/M939 etc, 11602160

Does anyone know if this switch will work and operate correctly for this application? I don't see why it wouldn't. The only questions I have is if it has the same thread size...

If anyone knows about this, any input would be appreciated!
Thanks!


---------------------------------
UPDATE:

Hey All, I received the "brake" pressure switch today. It has a 3/8" inch size threaded fitting, where the original pressure switch was only 1/8" inch threaded fitting.

So I had to take a trip to to home-depot and pick up some adapters, to adapt it from 3/8" to 1/8" They didn't have a single adapter that work do it, so I had to use a couple pieces to get to the right sizes. As long as you have the room, its no big deal, just use a good thread sealant tape, and properly tighten.

If you don't have the room for the extra length gained by adding the adapters, you might consider adding a 90 Degree elbow like I did. I had already installed this just to have plenty clearance between the switch and a 12v power socket I had added. But it now became necessary to have the 90 when adding the adapter pieces to this new switch.

All in all, it was easy to adapt, and easy to install. And it works perfect!

This is an easy fix to replacing the old pressure switch for the front axle engagement switch light. And its also much cheaper than buying the whole front axle air-shift assembly at around $150. This replacement pressure switch only costs $45 from Eriks, which is the link in my original post. Might even find it cheaper somewhere with further searching , or you might even have an extra.

After the install I fired up the truck, and as the air pressure began to build up somewhere around 30psi, I flipped the Axle Shift Switch Lever. The light came on just as it should. I ran the truck a few more minuets, and let the pressure build up to full. Tried the switch a few more times, and it worked every-time. So we shouldn't have any more problems with the axle switch after this repair.

I know how you guys like photos (just like I do)
So I took a few shots of the parts, install, and completed setup, and posted them below. Thanks Everyone!View attachment 326629

 

[steelandcanvas]

Sorry, no it won't work. The brake light switch closes a set of contacts when the correct pressure is applied to it. The axle engagement switch, is a valve and a set of contacts in one package. The valve allows air to be sent to the transfer case to engage the front axle. The switch portion allows the indicator light to come on when the valve is open. Take yours apart and see if you can't clean it up.

 

[Commander5993]

Hi SteelandCanvas!

Yes I have taken apart the valve assembly and cleaned everything. Connected the pressure switch up my air-compressor and used voltage tester to test for continuity "with pressure" and "no pressure" but didn't get anything either way.

The electrical pressure switch does unscrew from the valve assembly. The switch looks almost exactly like the brake light switch, once it is removed from the valve assembly.

I took your photo, and added some text and arrow to point out the pressure switch.
Then I went and got my pressure switch which I already had removed, and took a photo of it.
As you can see in the photo, I also have removed the two small screws and the rubber boot, so all you see is the two electrical connections.

As you can see, it looks nearly identical to the "Brake Light" Pressure Switch.

So What do you think?

Thanks for the Reply S&C!

 

[Commander5993]

BTW Like Your "Rank"
"The Anti-Bobber"

 

[CanonNinja]

worst case, you buy the entire air shift kit for $150 and keep the rest as spare parts? I've already done 2 air shift piston repairs, so those parts may come in handy

 

[phil2968]

I think it will work. Worst case is you wind up with a brake light switch. You can always use one of those. My light does not work either. I should check it out for the same problem.

 

[Commander5993]

That's true Phil, I think I'm going to go ahead and try it. I don't see any reason that it wouldn't work, as they operate the exact same way (when pressure is applied, contacts close). And like you said, worst case, I got an extra brake light switch.

I'll order it today, probably won't get it until mon or tue. Once I receive it, and get it installed, I'll post an update if it works or not.

 

[73m819]

YES it will work, the air switch just turns on pressure or dumps it, it just puts pressure to the light switch as it puts pressure to the transfer, the light pressure switch is NOT part of the air switch but part of the air shift control unit. the AIR SHIFT light pressure switch is the SAME as the BRAKE LIGHT pressure switch, either one can be used for either function, or for that matter any time a switch is needed to convert pressure to activate a electrical circuit.

 

[steelandcanvas]

CMDR5993, My apologies, I completely mis-understood you. I thought your were trying to replace the existing unit with the brake light switch, hence the basic explaination of how the switch works. I am in agreement with the others, I see no reason why the replacement brake light switch wouldn't work. I gotta quit staying up so late. Let us know how that switch works out for you.

 

[Commander5993]

Take yours apart and see if you can't clean it up.

Hey S&C, I was just looking at your photo of the front axle air switch dis-assembled in reply #2. and it looks like your switch has a plastic "piston"?

Mine is metal with an o-ring. I hadn't put my lever back in yet, so I took the piston back out and took a photo. Wonder what the difference is (besides one being plastic and one being metal )

 

[steelandcanvas]

I think you have the "super deluxe" style, mine is all plastic, extremely cheesey, and off my '87 Deuce. I'll have to look and see if the '71 deuce might have a better quality unit. The pistons are entirely different. Strange.

 

[Commander5993]

I think you have the "super deluxe" style

mine is all plastic, extremely cheesey, and off my '87 Deuce. I'll have to look and see if the '71 deuce might have a better quality unit. The pistons are entirely different. Strange.

Our deuce is a '68 so your '71 may look closer to my "super deluxe" model

 

[Commander5993]

worst case, you buy the entire air shift kit for $150 and keep the rest as spare parts? I've already done 2 air shift piston repairs, so those parts may come in handy

My Axle switch is fine, tore it down, cleaned & oiled, and checked the o rings. Plus apparently, my switch is better than the "newer" style, as the piston and all is metal (minus the rubber orings). So I shouldn't have any problems there.

Plus I really don't want to spend $150 when $45 will work

Thanks for the reply though!

 

[Commander5993]

Just added an Update & Photos to my OP (Original Post)

The Short Version: Received the switch today, got it installed, and it works Perfect!
Read the update in the OP for full details!

Thanks Everyone for your Comments, Suggestions, and Input!

 

[jbsapp]

I think Saturn has the whole kit-n-caboodle for $75. At least, I hope so, as I have one on the way to my front door. NSN 2520-00-113-8049

Saturn Surplus

 

[Commander5993]

$75.00 isn't bad for the entire kit, especially since you get all the wiring, data plate, etc.

To be honest, I didn't look on saturn this time. Had a few problems with them before, mostly when they are sold out of something, and they just "take off" that item from my order, then send the rest of your order anyway. Its not a big deal, but a time or two, the "item" they were "sold out of" or no longer stocked, was the whole reason for my order. If they had contacted me and told me they were sold out, I would have just canceled the order.

In any case, hope you get your kit
Thanks for posting the part number and page link, might help someone else out later.

I'm just glad mine is fixed, working, and complete

Now I just have to finish the wiring on my brake air pressure switch, and my low air pressure switch... and then get everything else completed on the truck.

 

[steelandcanvas]

Cmdr5993, You do some very nice work my friend! In your update photos, it looks as though you have a single switch plate for all your accessory controls, indicators, switches, etc. Very nice idea instead of having a bunch of different mounts hanging down under the dash. Do you have a photo of a full view of the single switch plate?

 

[Commander5993]

Hey SteelAndCanvas!
Thanks for the comments! My Dad and I have been working on our Deuce for the past 3 months. Done a ton of work. Some of the work was to update or add, but much of it has been maintenance and repair work. The truck was supposed to have been "lacking nothing".... well the seller just plain lied. It needed a lot of work.

But in any case, we are finally nearing completion. We were replacing all the brake hoses today, then some storms came through. I went back out after that and took a couple photos of the dash.

The accessory panel is just a simple piece of 16 gauge steel, which I held in a vice, clamped between two pieces of angle iron to keep it straight, and then we bent it to create the proper angle for the attachment points to the bottom of the dash.
It holds most of the accessory items we have added to the truck. Including all the heating controls, parking brake light, low brake fluid light, digital "12 volt" system voltage gauge, 2 - 12 volt power sockets, USB charging port, and 5 accessory switches. We wanted to keep everything together, held securely, but easy to reach. Its not perfect, but it works. Don't have a machine shop or anything, just some hand tools, angle grinder, air drill, etc. Enough to get by.

Anyway, I attached a couple pics of the panel below. Once we get the truck complete, I'm going to start a new thread and show the truck in full.

Thanks Again!

 

[toddm]

Nice looking dash! My air shift indicator light did not work, I checked everything out finally bought a stop light switch and a 1/8" adapter from my local Peterbilt dealer for about $18 and I got it right away. The light works as it should now.

 

[steelandcanvas]

It holds most of the accessory items we have added to the truck. Including all the heating controls, parking brake light, low brake fluid light, digital "12 volt" system voltage gauge, 2 - 12 volt power sockets, USB charging port, and 5 accessory switches. Thanks Again!

Commander 5993, I'm assuming you added a remote reservoir with a liquid level sensor to your brake system, since you have the low brake fluid light. Can we sneak a peek at that setup? Maybe a part number or two? I really like your whole approach with the panel
for your accessory controls, switches, and power sockets.