4WD electronics

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dokatd
United States of America
Posts: 257
Joined: Sun Nov 30, 2008 8:13 pm

4WD electronics

Post by dokatd » Mon May 11, 2020 7:13 pm

So of course the 4WD is actuated by the valve in the rear cab behind the passenger seat. This valve is 24v. My truck is now 12V. This is one of the final items I need to fix so I don't have to manually engage 4WD. I tried a regular 12V valve but two problems have come up. One is the valve is maybe not well suited to the pressure as it seems to get really hot. Second the circuit doesn’t seem to work in 12V mode. It will turn the 4WD off without issue but I cannot get the system to engage 4WD. Seems the system just breaks the ground in one of a few places. But something is not right. Holding someone here knows the system well enough to explain.

Joeri
Belgium
Posts: 55
Joined: Sun Jan 05, 2020 11:09 am

Re: 4WD electronics

Post by Joeri » Tue May 12, 2020 12:35 am

I,m not Sure but if you put it in low gear isnt it suposed to activate the 4x4 automaticly ? It has been some time that i've owned a c303 or tgb1111 :mrgreen:

dokatd
United States of America
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Re: 4WD electronics

Post by dokatd » Tue May 12, 2020 9:25 am

Yes, low range is one of the multiple conditions that will turn on 4WD.

Uli-RT
Germany
Posts: 65
Joined: Wed May 16, 2012 7:27 am
Location: Baden-Württemberg

Re: 4WD electronics

Post by Uli-RT » Tue May 12, 2020 3:12 pm

If 4WD ist NOT engaged, the Valve is working.
Without electricity the Valve opens, and 4WD is engaged.
If you can hear the Valve, may be there is some dirt in the air intake of the valve.
If you take of the hose of the Valve 4WD should be engaged.

dokatd
United States of America
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Re: 4WD electronics

Post by dokatd » Tue May 12, 2020 6:43 pm

Remember, this is now a 12V system. The old valve has been replaced with a new one. My problem is that the circuit is not breaking so I can’t select 4wd. Nothing else in the circuit should be voltage dependent. Or so I assume.

Joeri
Belgium
Posts: 55
Joined: Sun Jan 05, 2020 11:09 am

Re: 4WD electronics

Post by Joeri » Wed May 13, 2020 12:56 am

Well i thought that these solenoids where located on the right side of the engine....there are 2 solenoids there not sure :oops:

dokatd
United States of America
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Re: 4WD electronics

Post by dokatd » Wed May 13, 2020 9:54 am

To my knowledge there is one solenoid in the stock setup. It’s the one mounted to the wall inside the cab behind the back seat heater. It is connected to Vacuum and then to the bellows that actuates the 4wd. Bet I can tell is that the switch on the dashboard is the first line of defense and it cuts power to the solenoid. Then maybe there is a switch that watches for the lockers being activated? Then there is the brake pressure switch that activates if the brake line pressure pre booster exceeds a certain point. But that all seems to be basics contact switches and they should not be voltage dependent.

Uli-RT
Germany
Posts: 65
Joined: Wed May 16, 2012 7:27 am
Location: Baden-Württemberg

Re: 4WD electronics

Post by Uli-RT » Wed May 13, 2020 12:01 pm

Are you shure that the new Valve is working the right way?
It should open if you put power on it.
If it is closed, you have vakuum and 4WD is OFF.

dokatd
United States of America
Posts: 257
Joined: Sun Nov 30, 2008 8:13 pm

Re: 4WD electronics

Post by dokatd » Wed May 13, 2020 10:30 pm

Appreciate the help, I’m still stumped but the suggestions are good. Here is what is working

• Ignition off - no power and valve is allowing the 4wd bellows to be open to atmosphere (4wd engaged)
• Ignition on - valve actuates and draws vacuum on the bellows (2wd engaged)
• 4wd button depressed - nothing happens and truck stays in 2wd.

The system worked perfectly prior. I’m curious about the multi pole switch attached to the back of the t-case. Does that have anything to do with it? Seems it may be the switch that tells the truck it’s in low range and to set 4wd on. Maybe I have something wrong there?

dokatd
United States of America
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Joined: Sun Nov 30, 2008 8:13 pm

Re: 4WD electronics

Post by dokatd » Wed May 13, 2020 10:45 pm

Think the T-case switch is my problem. Think I accidentally wired the solenoid up to ground. Image

dokatd
United States of America
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Re: 4WD electronics

Post by dokatd » Thu May 14, 2020 6:25 pm

Does anyone have a pic of their t-case showing the wires in and out of the switch just above and forward of the parking brake drum? There are two black/whites and two solid blacks.

dokatd
United States of America
Posts: 257
Joined: Sun Nov 30, 2008 8:13 pm

Re: 4WD electronics

Post by dokatd » Mon May 18, 2020 8:37 pm

Ok, my truck supplier in Sweden got me sorted out.

Wires go opposite each other on the switch. One orientation works the other does not. Meaning it’s either black with white trace on top and bottom and solid black on sides or rotate all 90degrees if first orientation does not work.

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