Electrical/Electronic Mods to our Oka

Being an electronics engineer it was inevitable that I would make and installed lots of electrical/electronic modifications and additions to our Oka.

None of these mods affect the basic functionality of the Oka, in fact there is only one essential electrical item which keeps the engine running or not, which is the fuel cut off solenoid on the injector pump.

As long as you can start the engine, the solenoid wire with 12v applied is the only electrical thing needed to keep it running. See this post for the minimum electrics to start and keep the engine running.

Electrical Mods to our Oka (** indicates my own design/construction)

Mods which relate to Driving

• Smart alternator regulator for our 120A alternator (Sterling AR12VD)
• Triple batteries with automatic charge connection and manual paralleling switches**
  • Supercharge Gold MF95D31R (760 CCA) starter battery
  • 2 x Supercharge MRV70 (105 AH, 760 CCA) Allrounder (Starting and Deep Cycle) house batteries
• Solar panels (200W, 10 x 20W) and multiple battery charge controller**
• Charge monitoring display system (current and voltage)*
• Start Lock Out system**
  • Prevents the engine from being started until an enable button is pressed, after the ignition is turned on
  • Fitted with an emergency engine stop button
• Reversing and forward facing (for seeing over crests) cameras and 9 inch LCD display
• Wiper delay system**
  • 6 delay periods
  • 1 or 2 wipes per cycle
• Dashboard electronics**
  • Voltage and charge current meters switchable to each battery (LCD and LED)
  • GPS PSU
  • Turbo Timer
  • Headlight/Step/Vent/Pump “Left On” reminder system
  • Laptop PSU for moving map system**
• Remote central locking doors**
  • Fitted to all 3 doors, with interlocks so that any internal door handle can lock and unlock all doors**
• Electric windows on both front doors**
• Remote switching of fridge dc**
  • Allows fridge to be switched off from cabin when stopped (eg for fuel), to reduce battery load. Normally the fridge runs from 240v ac via the inverter while travelling as it’s more efficient than dc, less cable losses. Solar panels provide power when the alternator is not charging
• Automatic inhibit of Water Pumps**
  • Inhibits pumps when the ignition is ON, to prevent accidental pumping out of water if a pipe leaks or breaks while travelling
• Diesel Transfer Pump to transfer fuel from rear to side tank

Mods which relate to the Motorhome

• System switch functions for all rear electrical equipment**
  • Pumps, Lights, Fans
• Water Level Meters for both main water tanks**
• Fridge/freezer monitor and alarm system**
  • Display of fridge and freezer temps
  • Over temp and flame failure alarms
  • Indication of energy source (ac, dc or gas)
    •  Note: Fridge is normally powered from ac inverter while travelling
• Fridge Fan to circulate cold air, stops when door is opened**
• Fridge LED Lights which operate when door is opened**
• Window Fans to cool us at night (speed controlled from quiet breeze to gale force)**
• 300W Sine Wave Inverter (Jaycar) with RCD
• Soldering Iron, 24v 60W, temperature controlled, runs from dc-dc converter**
• Drill battery charger, 24v, microcomputer controlled
  • Runs from same dc-dc converter as soldering iron
• Computer systems
  • GPS moving map system based on MacBook, USB GPS and Oziexplorer running under VirtualBox and XP
  • 17 inch LCD display mounted on engine cover
  • NextG Phone/Modem,( plugs into MacBook), with external whip and Yagi antennae
  • 2 x 40W channel HiFi system switchable from radio to computer**
• Smoke Alarm inhibitor**
  • Prevents activation while cooking. Manual reset or automatic reset after 40 minutes
• NiCd/NiMH Battery Charger (up to 10 batteries at once)
• Rechargeable Dolphin LED Torch using 8 1/2 W LED’s and 6v SLA battery**
• Dustbuster converted to run from 12v (internal 12v to 6v switching converter)**
• HF Radio, (Codan 7727 with VKS737 frequencies)
  • Modified to receive ABC and BBC shortwave broadcasts
  • Allows transmit/receive on the 40 meter (7 MHz) amateur band (call sign VK5MDR)**
  • Frequencies can be selected via an external VFO**
  • Allows broader range of emergency frequencies
  • Jenal SC2 microphone fitted to allow direct RFDS connection via Selcall though VKS bases**
  • Tapped whip and 9m Super Rod antennae
• SW Battery Radio
• LED Lights**
  • External LED camping lights
  • Internal LED lights
  • Automatic porch/step lights (comes on at dusk when door is opened)
• Fridge dc low voltage cut off**
• Roof Vent fan speed control**
• Evaporative air conditioning controls**
  • Controls small evaporative a/c for use when the engine is off
  • Provides automatic shots of water to keep the evaporator pads damp instead of a continuous supply, to save water. Uses a timer to control a solenoid valve from the pressurised water supply

Electrical/Electronic Mods to our Oka

Being an electronics engineer it was inevitable that I would make and installed lots of electrical/electronic modifications and additions to our Oka.

None of these mods affect the basic functionality of the Oka, in fact there is only one essential electrical item which keeps the engine running or not, which is the fuel cut off solenoid on the injector pump.

As long as you can start the engine, the solenoid wire with 12v applied is the only electrical thing needed to keep it running. See this post for the minimum electrics to start and keep the engine running.

Electrical Mods to our Oka (* indicates my own design/construction)

Mods which relate to Driving

• Smart alternator regulator for our 120A alternator (Sterling AR12VD)
• Triple batteries with automatic charge connection and manual paralleling switches*
• Solar panels (200W, 10 x 20W) and multiple battery charge controller*
• Charge monitoring display system (current and voltage)*
• Start Lock Out system (prevents the engine from being started until an enable button is pressed, after the ignition is turned on)*
• Emergency engine stop button*
• Reversing and forward facing (for seeing over crests) cameras
• Wiper delay system*
• 6 delay periods
• 1 or 2 wipes per cycle
• Dashboard electronics*
• Voltage and charge current meters switchable to each battery (LCD and LED)
• GPS PSU
• Turbo Timer
• Headlight/Step/Vent/Pump “Left ON” reminder system
• Laptop PSU*
• Remote central locking doors (all 3 doors, with interlocks so that any internal door handle can lock and unlock all doors)*
• Electric windows on both front doors*
• Remote switching of fridge dc (allows fridge to be switched off from cabin when stopped (eg for fuel), to reduce battery load)*
• Automatic inhibit of Water Pumps (inhibits pumps when the ignition is ON, to prevent accidental pumping out of water if a pipe leaks or breaks while travelling and the pump is on)*
• Diesel Transfer Pump to transfer fuel from rear to side tank

Mods which relate to the Motorhome

• System switch functions for all rear electrical equipment*
• Pumps, Lights, Fans
• Water Level Meters for both main water tanks*
• Fridge/freezer monitor and alarm system*
• Display of fridge and freezer temps
• Over temp and flame failure alarms
• Indication of energy source (ac, dc or gas)
•  Note: Fridge is powered from ac inverter while travelling as it’s more efficient than dc, less cable loss
• Fridge Fan to circulate cold air, stops when door is opened*
• Fridge LED Lights which operate when door is opened*
• Window Fans to cool us at night (speed controlled from quiet breeze to gale force)*
• 300W Sine Wave Inverter (Jaycar) with RCD
• Soldering Iron, 24v 60W, temperature controlled, runs from dc-dc converter*
• Drill battery charger, 24v, microcomputer controlled
• Runs from same dc-dc converter as soldering iron
• Computer systems
• GPS moving map system based on MacBook, USB GPS and Oziexplorer running under VirtualBox and XP
• NextG Phone modem, plugs into MacBook, with external whip and Yagi antennae
• Smoke Alarm inhibitor (so it doesn’t activate while cooking. Manual reset or automatic reset after 40 minutes)*
• NiCd/NiMH Battery Charger (up to 10 batteries at once)
• Rechargeable Dolphin LED Torch using 8 1/2 W LED’s  and 6v SLA battery*
• Dustbuster converted to run from 12v (internal 12v to 6v switching converter)*
• HF Radio, (Codan 7727 with VKS737 frequencies)
• Modified to receive ABC and BBC shortwave broadcasts*
• Frequencies can be selected via an external VFO*
• Allows broader range of emergency frequencies
• Jenal SC2 microphone fitted to allow direct RFDS connection via Selcall to VKS bases*
• Tapped whip and 9m super rod antennae
• SW Battery Radio
• LED Lights*
• External LED camping lights
• Internal LED lights
• Automatic porch/step lights (comes on at dusk if door is opened)
• Fridge dc low voltage cut off*
• Roof Vent fan speed control*
• Evaporative a/c controls* (provides shots of water to the evaporator pads instead of continuous supply, to save water)

Where We Store Stuff in our Oka

We need to know where we’ve put things which are not used on a regular basis, like spares and tools, so I keep a list.
Also see this post for photos of other storage areas we’ve created around our Oka.


Black Hole Box
(This is above the cabin inside our raised roof. It’s dark in there, hence the name)

            Awning
            Engine spares (light weight) in plastic box
                        Belts
                        Fuel filter
                        Gloves
                        Hoses
                        Oil filter
                        Radiator repair stuff
                        Safety glasses
                        Thermostat and gaskets (2)
                        Water pump gasket
                        Welding glass
            Jumper leads (canvas bag)
            Kettle (dirty black campfire kettle)
            Screen room (pop up 2m x 2m x 2m insect proof tent)
            Snorkel and flippers

Front PVC Pole Pipe
(This is a 120mm diameter x 2m PVC pipe with screw caps mounted just behind the top of the front bullbar)

            Antenna poles (to extend the NextG Antenna height)
            Awning poles
            Earth stake
            Lengths of tube and strips of aluminium and timber
            Sand Flag pole (mounts on front bullbar in sand dune country. Also useful for hoisting a wire antenna 4m into the air)

Rear Compartment
(The rear compartment is inside the rear hatch, on the floor, but behind a bulkhead so things can’t fly forwards in a sudden stop. It’s used for heavier tools, equipments and spares)

            4 inch vice
            Air drill and grinding disks
            Heavy tools in cardboard box
                        Breaker bar
                        Clamps
                        Grease and grease gun (in sealed bag)
                        Hammer
                        Large files
                        Large screw drivers
                        Large spanners

                        Jack handle

                        Rubber hammer

                        Tyre levers

                        Wheel brace
            Hose clips
            Jerry cans for fuel, 1 or 2 when required
            Plastic box of spray chemicals
                        Brake cleaner
                        IPA
                        Silicone grease
                        WD40
            R pins
            Silicon, glue, gasket goo and Loctite
            Snatch strap and Equalisation strap (Winch/Tow Strap and Bow Shackles in external side box)
            Sockets (heavy) and torque wrench
            Spare nuts, bolts, washers and screws
            Square steel container (a 10 L campfire oil drum) containing:
                        Brake fluid
                        Diff oil
                        Engine and transfer box oil
                        Hydraulic oil
            Suspension bushes
            Tarp
            Welder hand tools and rods and gas blow torch

Rear Gate Tool Boxes
(These are boxes built into the skin of the rear gate hatch after removal of the internal steel panel)

            Allen keys
            Clamps, files, tie wraps, tent pegs and raw materials (LHS)
            Hex screw drivers
            Saws, chisels and cutting equipment (RHS)
            Small sockets and drivers
            Small spanners
                        A/F and Whitworth
                        Metric

Rear Overhead Compartment
(This is one of the internal overhead compartments built into the raised roof. Other compartments are used for domestic storage)

            Box of wire
            Electric terminal kit
            Electronic components
            Shortwave Radio
            USB keyboard
            Yagi antenna beam (for NextG phone/modem)

Seat Compartment
(This is a long compartment built below a seat alongside our kitchen unit)

            Chairs
            Hessian sacks
            Hub adaptor and bearing puller
            Sand mats
            Spade (small)
            Table top
            Table leg
            Wheel brace extension bar
            Wooden and plastic strip

Shower Recess
(When not used as a shower we store lightweight bulky things in it)

            Hanging rails for damp clothes
            Laundry equipment
            Padded Milk Crate (used as a seat/step), containing
                         Wine casks
                         Dirty clothes bags

            Screens for all rear windows to provide heat and light insulation

                         Made from Aircell aluminium bubblepack insulation from Bunnings

                         Fitted with suction caps

            Spray water bottles for very hot weather
            Toilet tent

Side Box
(This is an external steel box mounted behind drivers wheel mudflap)

            Bow shackles (2 x 4.75 tonne)
            Ropes various
            Winch extension strap (used as a tow/object removal rope)

Under/Behind Drivers Seat

            Behind seat
                        Emergency Rucksack above computer box
                        Flashlube and funnel
                        Rubber Gloves
                        Thin box with hand tools, pliers, small screw drivers, small adjustable wrench
            In wheel arch box (accessible from under the seat)
                        Bearing locknut socket
                        Bearings (s/h)
                        Brake pads (1 of each)
                        Clutch cable (used, but usable for repair of cables)
                        Gas bottle to airline pipe (emergency tyre “air” source)
                        Hi Lift jack extension (for winching)
                        Hi Lift jack overhaul kit
                        Lift Pump and gasket
                        Spring repair kit (allows spare half leaf to be used to repair broken spring eye)
                        Suspension pins and bushes
                        U-Bolt and nuts

Under/Behind Passenger Seat

            Behind seat
                        Airline (small), tyre pressure gauge and air blower tool (in canvas bag, behind seat)
                        Screens for the windscreen and front door windows (same type as for rear windows)
                        Tyre repair kit (behind passenger’s seat, under library)
            In wheel arch box (accessible from under the seat)
                        Bearing lock washers and tab bending puller
                        Bearings (new)
                        Brake parts
                        Free wheeling hubs spares
                        Gear ball joint
                        Oil seals
                        Spare  UJ
                        Split pins

Under Rear Bed/Seat
(This compartment is under the seat/bed base and shares its space with a 50 L reserve flexible water tank)

            Drill bits, drill and battery
            Electric tool kits
            Small hex screwdriver kit and small fixing screws
            Small Stanley socket set

On the Rear Gate
(The rear gate is for holding one of the spare wheels but we also use it for storing other external items)

            Coiled airline mounted on a 120mm diameter PVC pipe (covered to avoid the effects of sunlight/ultraviolet)
            Levelling wedges (won’t be used so much now we have airbags all round but useful as chocks or small sand mats)
            Long handled spade (extension handle inside PVC pipe)
            Water hoses (long and short) coiled up inside the spare wheel
            Water tank/tap connectors, inside airline PVC pipe

Under Wheel-Arch Storage Boxes

Our Oka is a bus model converted to a motorhome so there is limited internal space for storage of heavy spares, except in the rear hatch area. However that area is behind the rear wheels and, with a heavy spare wheel gate mounted across the rear, results in a lopsided (lop-fronted?) front/back weight distribution.

So I’m always on the look out for additional external storage areas on our Oka, especially low down (for heavy objects), to relocate weight from the rear to the front/middle and to free up rear space.

For sometime now I’ve been eyeing up the cavernous space under the front wheel arches. We previously fitted water tanks under the wheel arches of an old Land Rover for a round the world trip so I know it works, if you leave sufficient space for wheel movement.

The huge space under the front wheel arches was just begging to be used

Further on I’ve describe how I made use of this space with some simple boxes, accessed from under the seats, but first, here are some of the external storage spaces we’ve already used.

Spaces Already Used

Making use of the wheel arch space came only after we’ve already used pretty much all the obvious spaces on the Oka:

• the area behind and alongside the fuels tanks for:

10 litre removable waste water tank and 4.5 kg gas bottles

• the space outside the RHS fuel tank for a thin water tank (made from 90mm PVC pipe to hold 25l of shower water),

25 litre “snake tank”. People called it a snake tank, so Janet painted a serpent on it.

• the space behind and below the passenger seat (directly opposite the air filter) for:

A 3rd battery. There is still a big unused space above the battery.

• the spaces under the rear bull bars for:

A reserve gas bottle on the LHS

A frame for a jack and 2 axles stands on the RHS (empty in this photo)

• the space behind the front mud flaps for:

Water containers and air compressor controls on the LHS

A box for recovery gear on the RHS (winch strap, bow shackles, rope etc)

• the space below the centre of the floor for 2 water pumps, gas regulator, and gas and water tank change over taps (accessed via a floor hatch).

Internal floor hatch

• on the front bullbar a Hi Lift jack is stored, together with 2m of 125mm PVC pipe used to hold awning poles, sand flag pole, antenna poles,

Hi Lift jack and pole storage pipe on front bullbar

• on the rear wheel ladder we have a coiled airline pipe, water hoses, a pair of levelling wedges and a long handled spade,

The rear gate is full up with stuff

• the rear hatch internal space is modified to use as 4 separate tool boxes, with the top as a work bench.

Rear hatch tool box mods

Rear hatch in use as a tool box and work bench

Front Wheel Arch Space

The space between the top of the front tyre and the bottom of the floor plate is at least 200mm at the absolute maximum possible travel of the suspension (with 285 x 19.5 inch tyres), so I have fitted a 125mm deep box under each wheel arch, which should allow adequate worst case clearance.

Storage box mounted under the drivers seat. It would be better if they fitted right across the available space. The shock absorber has room to move and its bolt is still accessible.

I did have to identify possible strong points for mounting the boxes and watch for the location of, and access to the shock absorber mounts. These limit the available width of the boxes to about 200mm, without intruding on the wheel spat area, or making the mounting/sealing arrangements unnecessarily complex.

I happened to have a long aluminium box originally designed to hold 2 jerry cans on a roof rack, so I cut it in half, blocked up the open ends and fitted some mounting angles to the tops. At 500mm long, they are not quite as long as I would have liked, but beggars and choosers etc. It would be better if the boxes stretched the full 700mm right across the wheel arch to reduce the number of cavities that mud, water and dust can penetrate.

It would be an easy job to fabricate or adapt some simple boxes to fit. I did initially look at adapting some small steel tool boxes or army surplus “ammunition” type boxes before remembering my nice long aluminium box. Plastic boxes should be avoided however, since they will be exposed to high speed rocks, sand and water thrown up by the wheels, not to mention shock and vibration.

A long aluminium box cut into 2.

Access to the Boxes

Access is via a simple hatch door under the seat as they are intended for storage of rarely used items, such as wheel bearings, UJ’s etc. You wouldn’t want to store often used items here since removing the seat is a bit of a pain, but a side access plate could be fitted, bearing in mind it will be exposed to the elements and wheel driven sand, water, rocks etc., and it would need to be very secure.

Access hatch under the seat.

Simple slide-in hatch covers, held in place by M6 captive nuts.

Mounting the Boxes

The seat frames provide suitable strong points for mounting the boxes as you don’t want them to fall off, scattering your spares along the track. However, the bottom of the front base of the seat sits quite close to the frame so thin headed bolts (countersink or no washers) will be required or the seat fixing won’t locate correctly. I used M8 bolts.

Hatch cover in place. Note the mounting bolts on the seat frame. The 2 other bolts are close to the door frame.

While preparing the wheel arch I discovered (actually re-discovered) some rust holes in the floor plate around the seat frame. These needed to be treated before mounting the boxes.

I painted the boxes with under-seal for protection, and fitted thick foam sealing strips around the top surface (since the bottom of the floor pan is not flat) to reduce the ingress of the aforementioned mud, water and dust. I am always torn between fully sealing a container to keep out water and dust, or accepting the inevitability of leaks and fitting drain plugs. For these boxes I’ve attempted both. I’ve sealed them as best I can but provided blanking plugs on the bottom so that any water/dust that does penetrate can be more easily removed.

The Contents

The boxes have a volume of around 10 litres each, which doesn’t sound much, but it’s surprising how many spares you can fit into such a space.

The access hatch is around 150 mm square, but could be longer.

The kinds of things we store in these boxes are:

• Wheel bearings and cups (1 of each type), lock washers and tab bending puller
• Bearing locknut socket (2 1/2 inch box spanner)
• Freewheeling hub spares (the plastic bits inside can break)
• Gear ball joint
• Oil seals (rear hub)
• Spare UJ
• Brake pads (1 of each type), calliper springs, screws and clips
• Clutch cable (old but suitable for repairing clutch, throttle and handbrake cables)
• Gas bottle to airline pipe (emergency “air” supply)
• Hi Lift jack extension (for winching)
• Hi Lift jack overhaul kit (actually the old bits after overhaul)
• Lift Pump and gasket
• Suspension pins and bushes
• U-Bolt and nuts

I wrapped the heavy items in bubble wrap to protect them both from vibration and the possiblilty of water damage.

The result is that I have relocated more than 10kg of weight from our rear compartment to a lower point, nearer the front, and I’ve also freed up 20 litres of space in the rear.

Rear Towing Points on an Oka

If you have rear bullbars on your Oka, but no tow bar (we used the rear space for extra fuel tanks), rear towing points can be easily added if you have built in reinforced high lift jack points. This applies mostly to full body models.

Drill a 22mm hole (or whatever size fits your D or Bow shackle pin snugly), just behind the high lift jack points on the side plate of the bullbar frame. The hole should be low enough so the shackle can be lifted to at least the horizontal position.

22mm holes in the bullbar side plate

The D or Bow shackle will fit neatly through the jacking point and provide strong towing points on either side of the Oka.

Bow shackle located on the bullbar

The bullbar side plate is 8mm steel and is bolted directly to the Oka chassis using the same 16mm bolts provided for holding a tow bar. It’s the equivalent of the tow points built into the front bullbar and probably stronger. It’s also the primary member used by the high lift jack in raising the vehicle.

 

Using D or Bow shackles on both sides and an equalisation strap (or a tree trunk protector), the stresses can be shared and equalised between each bullbar when the Oka is being towed backwards, or while pulling another vehicle or object off a track.

Notes:

 

Shackles with at least a 4.75 Tonne rating are recommended (equivalent to 10,500 lbs). If you need more than this you probably need a crane not a tow truck.

 

A webbing strap will fit a Bow shackle better than a D shackle.

A steel plate or large washer with 22 mm hole could be welded to the side plate to stabilise the action of the shackle if required, or packing pieces can be added to the shackle pin as shown below.

Don’t leave the shackles attached whilst driving, the pins will vibrate loose and the shackle will drop off.

Bolt-on tow hooks area available in 4WD shops but they are not as reliable as as D or Bow shackles since you are dependent on the strength of a hook (not a closed steel loop) and the integrity of 2 small bolts. In any case I couldn’t find anywhere suitable to mount them.