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MB GPW G503 WWII Military Jeep Wiring Harness installation WW2 Restoration

Installing your wiring harness can be done by one person. Instructions are fair, but you want to make sure you run the lines correctly to avoid pinching.

This article applies to Ford GPW WWII Military Jeeps 

1. This article is to help you with the wiring of your WWII jeep. These steps will be using a 45 Gpw and 45 MB and the steps will be kept as generic as possible to help everyone. Thanks to Dave (Iowa) on the G for the additional reference.
First, verify you have installed your Firewall padding prior to starting to run wires though your firewall.

2. Next, be sure you have a print out of your electrical diagram.

Early Push Pull Switch Diagram

Late Rotary Switch Diagram

3. Assuming you have purchased a wiring kit from MV Spares or Vintage Wiring of Maine, prepare your wiring by separating the wires and clips where you can easily reach them.

4. Assuming that your tub is in a rotisserie, Install your main junction block on your firewall. Next, stretch out your Main Wiring Harness and connect the black and red wires to the junction block. This willl be your starting point.

4. Special Note: If you do not have a rotisserie, Chuck notes that you will want to push the harness through the firewall and wire up the main switch first. Once the harness is attached to the firewall, there is very little room to work with the main switch.

5. Next follow the main harness down from the junction block and install the wires to the Headlight Dimmer switch. Once you connect the wires, install the dimmer switch onto the tub.

6. Now, lets wire the Main Wire Harness to the back tail lights. Your tub should have clips along the path you see here in the picture. Loosely, run the wiring harness to the back of the tub as shown.

7. Next, layout the tail lights wiring, and connect them to the main harness. Look at your wiring diagram for details on the connections.

8. Many people start their cursing when trying to connect the connectors to the tail lights. You need to line up the notches because your going to push in and twist.

9. Here the tail lights wiring is laid out with the tub upside down. After the connectors have been attached to the tail lights you can easily see from the diagram where the wires are connected.

10. After you have the tail lights connected, inspect and use some electrical tape to cover your connections from your main harness to your tail light wires. Note: on the driverside you should have the trailer socket wiring that will go up into the tool box.

Click here for trailer socket wiring

11. Inspect your wiring one last time after both tail lights are connected. Use electrical tape to protect the connectors to the main harness.

12. Now attach your tail light wiring to rear panel (NOTE: there should be holes in your panel for the ACM II body, not sure about script or ACM I bodies)

13. Follow your main cables back to the front of the jeep and wire up the headlight foot dimmer switch pulling the excess main harness towards the front. Add clip to hold harness in place.

14. Now follow your main harness up the firewall. You should have a number of wires that will connect to the Junction box, and a thick piece that will go through the firewall to the main switch. Here, we show the junction placement. Now it is important here that you follow your wiring diagram. Connect the main harness to the junction block, and prepare to connect the additional wires that goes through the firewall into the main switch.

15. Run your wires from the main harness through your dash and connect to the Main Switch. Again, review your wiring diagram to make sure you hook up correctly. Here we show the LATE model rotary switch connections. In addition to the main harness, your Main Switch will need to be connected for the wires to the Ammeter and Panel lights. Connect All wires to the main switch here. You will have some additional wires hanging off for the ignition, fuel guage and amp gauge.

16. Follow your wiring diagram and install the panel lights.

17. Follow your wiring diagram and connect the Amp Meter to main switch. Late Model -Run the extra amp meter wire out the firewall and leave there for the time being. Early Model - Connect the wiring to the main switch HT terminal.
Click here for the for the early model main switch.

18. Now make the final connections for the Fuel Gauge.

Note: the fuel gauge must have a good ground connection.
Click here for the wiring of the fuel gauge

19. Install the circuit breaker that goes under the dash and bolts to the cross member in the center of the dash.

20. Early Models Only: Here you will wire up the filterette that goes under the dash as shown in the wiring diagram. Three wires will come out the firewall.

21. Early Models Only:You can run the wires out the firewall to the 2 junction block as shown. You can leave as is, we will come back to these after the head lights are wired.

22. Now move back to the Main junction. You want to make all the connections as shown on the wiring diagram. You will need to layout your headlight and Black Out wiring at this point as well. Don't forget the connection to the Steering/Horn wire.

23. The fender Black out light is kind of a pain. This wire has to run through the fender channel so you need to get some tie wire and pull it through as shown. Then connect it up to the junction as shown on the wiring diagram.

24. Now run the wiring for the headlights from the Main Junction. You should have two sections one for the headlights and one for the black out lights. Review the diagram and lay the wiring lengths out into position.

25. Now install the wiring to the small junction for the headlights and the black out lights. Similar connections as you saw with the tail lights. Snap each of the connections together, and wrap up with electrical tape.

26. Run the wires into each of the two head light buckets, and wire up as shown on the wirinig diagram. Follow the wires for the front black out lights as well.

27. Now add your clips above the grill and around your headlight lamp buckets. Also, install the ground connectors on your headlight buckets. You have two sets of wires. The headlight wires will ride the top of the grill with clips on the top holding the wires in place. The black out lights will ride along the bottom of the grill and have a clip to hold the wire in place

28. Next, wire up your Voltage Regulator. Note: this is shown as a late model with the additional filters.

29. Next, wire up your Generator. Be sure to polarize the generator before starting.
To Polarize your Generator :
A generator that sits around on the bench for a long time, or on that has been dropped during handling, may lose its residual magnetism. The momentary surge of current through the field coils that you give when you give when you polarize the generator is enough to restore the residual magnetism. Polarization amounts to electrifying the fields with a battery but it must be done in the right direction.
1. Complete installation of generator, regulator and wires
2. Engine dead, ignition off.
3. Connect a jumper lead to the battery terminal of the regulator and touch the other end of the lead to the regulator armature terminal for just a fraction of a second.
4. Just a touch and its done!!

30. Next, wire up your starter as per the wiring diagram.

31. Next, connect the foot starter, to the starter as per the wiring diagram.

32. And last, (Early models) connect your wires from filterette, and junction, then connect your Coil wiring as per the wiring diagram and your battery... you should be ready to go!!

33. Don't Forget!! be sure to install your Rubber or Felt (depending on your year of jeep) Grommets in your fire wall to protect your wiring!

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