Front lockout light

[sermis]

I have a 67 M35A2 that has an air lock for the front. The little red indicator light stayes on. I pushed a tree so I know that the axel is locking and unlocking, so why is the indicator light staying on.

 

[Recovry4x4]

There is a pressure switch right on that Assy. It's either failed in the closed position, wires have been bypassed or perhaps the valve is not releasing and it's still in AWD. Does it turn OK on pavement?

 

[Jones]

Mske sure that the front axle is definately, completely disengaged and not just partly released. (We flip our control back to "disengage" then back up until the light goes out). IF hanging up; the transfer case slider may be a little gummy, or the vent side of the air circuit may not be completely exhausting the air.
If the front axle has unlocked then the sending unit has to be sticking or the wire has chafed and is grounding.

 

[sermis]

From what I can tell it is releasing, guess all the way. Turning is ok with no jerking and when pushing a tree the front did not turn when disenguaged but did spin when enguaged. Air appears to be dumping ok.

 

[Recovry4x4]

there is a plug to the passenger side of the air switch. Remove that and check continuity across the 2 studs on the hobbs switch, not the removed wire. Do this before starting the truck and building air. If there is continuity and no air, that hobbs switch is bad.

 

[sermis]

OK either i'm blind or something. Looked at the swich on the dash, no wire conections, nothing on the T-case where the airlines are. Where else could the switch be?

 

[Recovry4x4]

They say a picture is worth a thousand words. Look at the 2 attached pics. You can see the indicator light at the bottom of the assy. The wire from that light goes into a rubber plug along with another wire. That 2 wire plug is plugged into the pressure switch (hobbs switch). If you unplug that 2 wire plug and check contunuity across the terminals inside the boot of the pressure switch, you can determine if the switch is bad. Do this test without air in the air tanks of the truck. The one pic has an arrow and says "Here". Thats where the plug unplugs from the pressure switch.

 

[rizzo]

that should do it.

 

[Recovry4x4]

Pokin fun at me Kevin?

 

[FSBruva]

Kenny-

Does the wifey know you had a front axle switch sitting on the stove?!?!

Matt

 

[sermis]

Well from what was posted I thought it was there however on mine there is no switch with wires or at least I did not see one. There is another airline comming off going to the passenger side of the truck. I will get under the dash and try to trace down the wires. Maybe it got put somewhere else.

 

[Recovry4x4]

Is there a wire going to the light? There must be if the light is on. Perhaps they just plugged in a hot wire to the light. That air line going towards the passenger side provides the air for the engagement operation. If you follow it, it will go to a bulkhead fitting right near the glove box on the firewall.
Matt, I took that pic late last night while she was working. I was able to clear the range before she came home and preserved my status. She goes on her UTA in 2 weeks, then I can finish baking the paint on the armor dome light for the M108A2.

 

[rizzo]

Pokin fun at me Kevin?

no, Its not real clear how the light is switched on to show the axle is engaged. Your pic shows that the light has nothing to do with the engagment of the axle but only with wether air preasure is sent to the t-case to engage the front axle.

I think your pic cleared it up.

but don't worry, I will think of something to poke fun at you, soon or later.

Maybe something about your addiction to little teeny 6x6's

 

[Recovry4x4]

Yeah, I like the smaller stuff for sure. No worries, I'm up for some proddin.

 

[sermis]

Ok I looked real close yesterday. There is no Hobbs switch. The wire comes out of the wiring harness and goes straight to the light. There is a petcock on the side of the switch where the Hobbs switch should be. This would explain why the light stays on all the time.

 

[Recovry4x4]

Yes, that explains it! Do you see the 2 prong connector under there anywhere that would connect to the hobbs switch?

 

[sermis]

No 2 prong coupler. there is on coupler wire #27

 

[sermis]

WOW that was big!!!!!!!!!!!!!!!!

 

[Recovry4x4]

Wow, I had to download and resize these pics just to view them. Try submitting pics in the 640x480 range. Wire 27 is the power feed for the instruments. A commercial 60 psi hobbs switch could be used. You can sub bullet connectors for the packards in a pinch. Wire the existing wire on the light to one wire feeding the hobbs switch and the other goes to the light. Whenever you open the air valve to engage the front drive, the air will close the contacts in the hobbs switch and the light will come on.

 

[rmgill]

Ok, I know what's going on here. That switch setup appears to be kind of funky. You need a brake air pressure switch installed, (add a 90° fitting so it's pointing forwards. You'll need a few wire connectors.

Your existing wire should be plugged into the pressure switch, then another from the pressure switch to the light. The system you have now looks like it'll just be on all the time no matter what. That valve on the side of the switch is odd. Why does that need to be there?