air leak under dash

crazyplowboy

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I drove my deuce to work and home today with no problems. After supper I started it up and heard a hissing sound. After looking everywhere if found the culpret. There is a switch or distribution block of some sort located just to the right of the steering column. There is a wire going from the bottom of it to the power switch, and a wire on the top that runs to the low air buzzer. An air line runs in to the front of it, and there is a cap lightly pressed onto a fitting on the right side. The air is slowly hissing from the capped off fitting on the right side. Is this supposed to do this as a pressure release or something? I looked all over trying to learn what it is, but could not find any info.

I will try to take some pictures tomorrow
 

OPCOM

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nothing should be hissing under the dash unless you have an opossum or old cat living in your truck. There are thre air-things under the dash. The buzzer, the windshield wiper control, and the stopcock. The stopcock is on the passenger firewall and usually has an air connection on it.
 

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54reo

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rofl

Seriously though, a pic would help, as OPCOM did lay out about all there is under the dash with air to it.
 

CGarbee

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It's been a while since I looked under the dash of one of my dueces, but don't you also have the line to the guage...? I blew mine out on a five ton last week (still need to take pictures of the blown line and the new one). Scarry how fast I lost system pressure when that line went south...
 

Barrman

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My Gasser had that cap start leaking as well. I pulled the entire block off and swapped it out with another one I had. No more leak. I then took the old one apart. Don't take it apart. There is a spring in there that flies real well.

Seriously, there is a movable plate in there that as you figured out, turns the low air warning buzzer on and off based on air pressure. My plate on the bad one had a crack in it. That is why air was leaking out of the side that normally should not have air on it. That cap is there for just that reason. Without the cap, I can see the wire connector getting propelled up toward the driver. Since the connector is actually about 2" long and 1/8" thick, you don't want that dart flying around the cab.

You may have noticed that the little cap that is leaking air screws into the block. Don't take the easy way out and just put a pipe plug in there. Pull the block off the truck, take it apart being carefull of the spring and inspect the parts. You might just have a dried out o-ring between the two halves of the switch.
 

crazyplowboy

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i finally got the pictures posted, i took it off the firewall to inspect it this evening and found that the top cap that holds the rubber plate in place was loose. it was allowing air to sneak around the diaphram and out the hole on the side. i cleaned it up real good and redampened the rubber. seems like problem solved for now.

where can i go about finding new wiring for under the dash? as you can see mine is looking pretty rough and i am starting on the long road to a new looking truck.
 

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Barrman

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Glad you got the air leak fixed.

Wiring is kind of an all or nothing endeavor in my opinion. The best thing to do is find a new front wiring harness. This will include everything from the plug under the drivers seat forward on the truck. Except for the 5 legged spider wire on the back of the gauge cluster. You have to buy it seperate.

Lots of places and people are selling "New M35A2" wiring front harness. There is one on E-bay right now matter of fact. However, if the harness had a big plug (About 1 " metal) with 2 large pins inside. It is a harness meant for a truck with a generator/bread box regulator. You will then need to buy the $25.00 generator to alternator harness adaptor set from Jeff at Frontline. Plus, the harness with the generator plug normally doesn't have the solid state blinker box plug or the plug for the blinker arm either. Another $50 from other sources to make that work.

Frontline and OD Iron both have new front harness' with the alternator and blinker set ups included. Before you pass out from sticker shock, subtract the $75-$100 you will spend on the non correct harness in add ons and shipping to make it correct. You will find they are about the same price in the end.

That answer you question?
 

crazyplowboy

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Yes absolutely, after I posted the last message i started looking around and found the ones you are talking about at OD Iron. Looks like a good project for the cold times heading this way.
 

otisroy

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Melbourne, FL
Anyone had their air shifter switch leak? The short hose between the shifter and the junction was leaking at the swivel so I swapped that out and all seemed good. I was testing to make sure it was shifting and and noticed that the switch was hissing some. I toggled it a bit and it stopped. Is that common?
 

littlebob

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I can't open, enlarge the picture. I have a similar problem. MY air pressure switch was leaking I took it off and capped it(son did it he's smaller). Is this whats in the picture?
I want to get a replacement before I get it on the road?
littlebob
 

otisroy

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It's actually the shifter switch. It will hiss a bit. I can toggle it about half an inch and hear the transfer case start to engage and back it off. Sometimes that will stop it. Dry rotted seal? Rebuildable? I'll miss with it some more after the holidays.
 
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