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Updated brake switch

Flyingvan911

Flyingvan911

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I have heard that the air switch is much better. The old switches are operated by pressure from the brake fluid. The new ones are more reliable. Others may have more info.
 
stancanpara

stancanpara

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If your current one stops working, then contact Saturn Surplus or OD for a full kit to change from the old to the new brake light switch... There is more to it than a single piece...
 
Jake0147

Jake0147

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The old switches have been known to fail in such a way as to allow brake fluid leaks, of a potentially catastrophic volume. They're not a "take it off the road right now" kind of thing, the same risk applies to master cylinders, wheel cylinders, etc. They are a good idea to update though (requiring as mentioned a little extra doing besides just the switch). When they fail it's more "all or nothing" and less of a slow progression or slowly sinking pedal like when the rubber parts fail.
 
rlwm211

rlwm211

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The reason you change the brake switch from hydraulic to air operated is because if the diaphragm in the switch fails, the BFS Brake Fluid Silicone can catch fire and burn the truck up. I saw a fire start under a deuce at MTA last year due to this.

The air switch was also used on the M275 so it is a fairly common part. All you need is the switch, a plug for the port where the old switch was installed and a tee and pipe nipple (1/4" I believe) and maybe a fitting to connect your airline to the tee.

The air switch goes in the same port as the service air line that runs to the back of the truck for a trailer.

Pull the skid plate and bolts on the bottom and the air pack will swing away from the frame enough to remove the air line, install the new switch and fittings and reattach the air line. Make sure the switch is not hitting the frame when you put all the bolts back in.

You may need to change the end(s) of your wiring harness to work in the air switch. This depends on which hydraulic switch you have already.

If you need more information let me know.

RL
 
Valence

Valence

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Old thread, I realize, but in my 5 years of deuce ownership this is the first time I've read about this (or at least understood enough to comprehend it).

Just to clarify - if the switch (the 2 Packard connection plug) is located as follows then it has already been upgraded to an air sensor.

image.jpg image.jpg image.jpg image.jpg image.jpg image.jpg image.jpg

See the second to last picture, with the airpack in the vise. If the sensor is located at the VERY end, where a plug can be seen nearest the camera (directly opposite of the big air cylinder), then that is the older style and should be upgraded when you rebuild your airpack.

This post has a picture of the old style:
http://www.steelsoldiers.com/showth...fect-Gentleman&p=592468&viewfull=1#post592468
 
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rustystud

rustystud

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rlwm211 said:
The reason you change the brake switch from hydraulic to air operated is because if the diaphragm in the switch fails, the BFS Brake Fluid Silicone can catch fire and burn the truck up. I saw a fire start under a deuce at MTA last year due to this.

The air switch was also used on the M275 so it is a fairly common part. All you need is the switch, a plug for the port where the old switch was installed and a tee and pipe nipple (1/4" I believe) and maybe a fitting to connect your airline to the tee.

The air switch goes in the same port as the service air line that runs to the back of the truck for a trailer.

Pull the skid plate and bolts on the bottom and the air pack will swing away from the frame enough to remove the air line, install the new switch and fittings and reattach the air line. Make sure the switch is not hitting the frame when you put all the bolts back in.

You may need to change the end(s) of your wiring harness to work in the air switch. This depends on which hydraulic switch you have already.

If you need more information let me know.

RL
Click to expand...
This is actually a fallacy as Silicone brake fluid needs a blow torch to get it to burn properly. The real reason the military went to the air switch is three fold. One: if the old style switch failed you could also loose all your brake fluid ! Two: the old style switch needed to be high pressure and when it gets old it is harder for it to make contact, thus no brake lights. Three: the newer style switch is much cheaper and is used industry wide so easily and cheaply replaced.
 
gimpyrobb

gimpyrobb

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Yes, if you have the old setup, with the switch on the hydraulic-pressure side, I would swap it over to the air side before you do anything else.

Good explanation with pics V!
 
D

DerekM

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Reviving this old thread.
Started the evening with thinking I needed a new brake switch. Now I am wanting to go ahead and do the updated switch on the air side.
Problem is, I can't find them in stock on any of the regular sites. There are two sites that had them, wanderfin and walfragoods. Didn't want to buy them from there because they seemed a little sketchy. Does anybody know where I could find P/N 12255668 in stock. Google is coming up bust.
 
Valence

Valence

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Last edited:
D

DerekM

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frank8003 said:
I put a new switch and wired it to an LED in the dash so I can see that the switch itself is functioning.
Click to expand...
Thought about doing this myself just to know for sure that they are working.

PaulV said:
I purchased the pneumatic switch conversion kit from Wanderfin 3 weeks ago. Received it in a week. They are legitimate.
Click to expand...
Thanks, I had never heard of them and couldn't find nothing on them other an their website. I just ordered their last kit, so hopefully it will be in before next weekend.
 
cattlerepairman

cattlerepairman

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IMHO this is a "must do" modification, given the age of the parts on our trucks. The mod plugs a port in the hydraulic line and removes one nasty potential leak. It is a safety upgrade to install the air operated brake light switch.

You can use a civy air pressure operated brake light switch from NAPA and you can source the plumbing parts fairly easily. Here is a thread about the install and it shows which parts you will need:
https://www.steelsoldiers.com/showthread.php?74240-Brake-light-switch-replacement

Civilan switch, part numbers and tips here: https://www.steelsoldiers.com/showthread.php?130915-Air-stop-light-switch-issue/page5
 
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73m819

73m819

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I do not understand the big deal about this change because all you have to do disconnect the wires, remove the existing switch, plug the fitting where the switch was, then install a air brake brake light switch in the service line, connect the wires, so the only things needed are a plug and a air switch which can be got at napa or any truck shop for cheap. So WHY pay for a special "KIT" just because the kit has military, m35, 819, ect. in it's name.
 
simp5782

simp5782

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73m819 said:
I do not understand the big deal about this change because all you have to do disconnect the wires, remove the existing switch, plug the fitting where the switch was, then install a air brake brake light switch in the service line, connect the wires, so the only things needed are a plug and a air switch which can be got at napa or any truck shop for cheap. So WHY pay for a special "KIT" just because the kit has military, m35, 819, ect. in it's name.
Click to expand...
Cause some people don't know how to research and repurpose existing parts and only buy from surplus dealers. I have folks call me all the time for tires but they call Memphis or Eastern for truck specific parts even though I have given them that big long spreadsheet for the 5 tons. Its like well if you want to pay more then go ahead but they use the same parts.
 
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