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1994 DD51T wiring diagram

Discussion in 'General Truck Info' started by SGMBilly, Jun 29, 2020.

  1. SGMBilly

    SGMBilly New Member

    Hello All,

    Does anyone out there have a wiring diagram for a 1994 Suzuki DD51T.
    Specifically the 4WD system. Trying to track down why my 4WD, axle and diff lock lights don't come on and not locking.
  2. Koffer

    Koffer Active Member

    There’s a silver box screwed (4wd controller) to the front firewall behind the clutch pedal way up high that activates the axle lock and diff lock , royal PITA to get to and not cheap to replace . Come across a few bad ones , been rebuilding them ,
    I’ll look around as I got the pin out of the box and switches written down plus a wiring diagram too
    Try to post soon
  3. SGMBilly

    SGMBilly New Member

  4. SGMBilly

    SGMBilly New Member

    Thanks for the reply. I have the controller out and yes a royal PITA to find and remove. Not much room to twist around. A pin out diagram would help a lot. Since the mini relays are good what parts have you replaced inside controller that gives a signal to the relays? Or anything you think it might be.

    I'm sure it's doable.
  5. Koffer

    Koffer Active Member

    I’ve been gutting them and installing self latching relay boards , it’s easier then trying to find all the parts and it seems the control chip craps out and it’s too much a PITA to find ( not been able to )
    I’ve done a few with just adding toggle switch’s too but doesn’t look as clean
    The stock controller has a lot of safety/over complicated checks and balances built in that just adds to more links in the chain to brake
  6. SGMBilly & Koffer,

    Brand new member, new (to me) DD51T & first post. Inoperative 4X4 Controller and possible fix

    I am chiming in as the 4X4 Controller on the vehicle I purchased wasn't functioning (caught on pre purchase inspection) and I read this post - after discovery and before purchase.
    The push buttons on the axle lock and diff lock were having no affect on front wheel engagement - no orange lights no 4wd dash light - nor was rear diff locking & no diff lock orange light and/or axle lock orange light.
    Dealer (large importer of these things) realized that this was a deal breaker for me.
    Dealer's mechanic was very familiar with the oft malfunctioning (and now discontinued) 4X4 controllers and had devised a "hot wired" solution with a 15 amp fused lead to both the Front axle VSV via toggle switch as well as the rear diff VSV (two independent switches from one fused hot lead) - put the toggle switches in the two adjacent blank off plates next to the stock axle lock and diff lock push button (these were left connected) . Fused 12 V hot lead from fuse block - through simple toggle (on or off) then directly to activation electrical lead at respective VSV via a tie in (energized the circuit).
    Here is the mechanical action and light show - ( I elevated all four wheels with jacks/stands - had a helper start the vehicle and engage).
    Lever select 2 High - No lights - rear drive only - no diff lock mechanical - open rear diff. (validated by locking one rear wheel mechanically) - no diff lock light- functions as designed
    Lever select 4 High or 4 Low - rear drive and wheels same as above - plus forward drive shaft engaged but front wheels are not engaged - no lights
    Lever select 4 High or 4 Low - energize forward axle VSV via the toggle - same as as above except now the front wheels are engaged (spin - open differential) - get 4WD green light in dash & axle Lock orange light in OEM push button switch. Now vehicle is functioning as designed in 4WD - drive to all 4 wheels via open differentials. Flip axle lock toggle off - front wheels disengage orange light in axle lock extinguishes.
    Diff Lock Toggle - If Diff Lock toggle is energized - it energizes the rear diff VSV. The orange light in the OEM Diff Lock switch will illuminate and it will mechanically lock rear differential - validated that both rear wheels spin at same rpm despite differing resistance on wheels. In this configuration it makes no difference what position the lever selector is in 2 High, 4 High, or 4 Low. I believe that this feature is not OEM (the ability to lock rear diff in 2 High).
    Now, I am very cautious about this setup (the ability to directly energize the respective VSV's directly without going through the controller - no safety interlocks). I am careful to have everything stopped before engaging the toggles (on or off).
    My plan is to remove the 4X4 controller - open it up if able, clean with electrical contact cleaner, clean grounds and reinstall, pull fuse on dealer mechanics hotwire, and see if I can reestablish OEM configuration. If successful, great, if not, I plan to replace the open toggles with guarded switch toggles (prevents inadvertent activation & "hopefully" makes you think before flipping the switch(s) @ 70 KMH) and continue to use the vehicle in current configuration with the operator being the only safety interlock & hope my differentials doesn't get smoke checked.
  7. Christopher Oswalt

    Christopher Oswalt New Member

    My 4wd controller went to Hades. The circuit board on the controller burnt something out. I have read something on another post that had pics and a wiring diagram of the front diff. There are 2 solenoids on the front diff. I brought power from the yellow wire on the connector for the 4wd controller to a flush mount toggle switch, with a red led light, and ran it to the front diff. From there, I spliced the 12vdc and the ground to the wires on the 2 solenoids at the front diff. When the switch is turned on, the 4wd light in the dash turns on and the front axle engages. I hope this will help someone out. These controllers are hard to find. Don't make the mistakes I made and wire the switch to the transfer case and the same looking switch on the front diff. These are switches that turn the indicator lights on and will blow a fuse. The solenoids on the front diff are side by side. They should be turned on at the same time.

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