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Electrical Stuff

Our truck has a bit of a complicated set of electrical circuits, as do most camper trucks. There are 2 separate sets of batteries, and 2 separate electrical systems.


24 Volt electrical system

One set is to start and run the truck. These are 2 12v batteries together in series, which gives us 24V. The headlights, indicators, brake lights, starter motor etc are all 24v which is the normal voltage for trucks. This has its own alternator, which generates current to charge the 24v “bank” of batteries.


12 Volt electrical system

We also have 3 12v batteries working together in parallel to give us a 12V supply. This is used for the camper body to power things like the fridge, freezer, internal lights, water pump for the sink and the gas cooker ignition and lights. This 12v circuit can be charged in any of 3 different ways.

1. By the engine. The engine has a 2nd alternator that generates current to charge the 12v battery bank. This is a great option when you are moving the truck every day or every few days. It’s not a large alternator, about 40amp or so and it’s enough to get the job done.

2. Solar panels. We have 2 large solar panels on the roof and these can generate up to 17amps of power in full sunlight. If the batteries are almost fully charged, the solar panel controller “backs off” the amount of current that is supplied to the batteries. If you switch on something during the day with the batteries full, the solar panel quickly (within seconds) creates more power, so we often charge laptops, camera batteries etc during the day, and not at night.

3. The third method is a mains connection to the truck, which charges the batteries. This is popular with most camping cars, but we have often gone for months with no electic hookup by the very nature of the places that we go.


This gives us a total of 5 batteries aboard, each of them the same so we have the option to swap some about if we hit trouble. Each one can hold 110AH, or Amp hours. In theory, this means each one can provide 10 amps of power for 11 hours, but in practice it’s a lot less than that, probably even less than half of that before the voltage drops so low they are not much use. For example, the engel freezer stops drawing any power if the volts are less than 11.5 (approx).


electrical diagram

Wiring diagram for the 1300L mog. note there are different versions depending on your model, identified by the chassis number.


Key to the wiring diagram


We are currently (October 2012) having a problem with the flasher unit. It got damaged when the alternator ran with no regulator providing 30V and heating batteries and all sorts of badness. Since then we’ve had no indicators. Having finally found the flasher unit, I took a look inside. I can safely say i have never seen such a complex bit of gear just to blink a few lights.


Inside of the flasher unit

I think the relay inside is fried

Original relay with wires still attached.

Original 12 pin relay pin locations

We have made a modification to the wiring to allow a cheaper replacement flasher to go in. This is the replacement unit:

electrical connections

The terminals are the same size and layout, but the wiring pattern is a little different.

Inside the new flasher unit showing the relay

Inside the relay, from the back.

The only identification or part number on the box. Sorry.

These are the sockets that plug into the flasher unit. On my Mog, there are 3 sockets, the 4 pin, the 6 pin, and a 1 pin. You move the wire from the 1 pin to replace the wire that was for C3 (3rd dash warning light) and your done.

Our rear light cluster is 100% LED. This is because we removed the standard lights and brackets in order to install some storage space, and then we used the low profile LED lights to save space in the boxes.


Also, We have 100% led lights inside, and in each of the presses as they can be large dark places!


220V in our camper

We get 220V AC (Standard household power in most of Europe) from 2 sources. The usual one is our on-board inverter, which uses the 12V battery bank, and provides 220V in the camper. We can also get 220V “Passed through” directly to our sockets when plugged in at camp sites. We have standard Irish/UK square sockets.



Second Alternator mount (Non Standard)

This mount allows a second alternator to run just below the engine. the bracket is not original, and is a once off, however it’s pretty simple to copy. Feel free!

Bracket with no belt fitted, hanging down.

Bracket with no belt fitted, hanging down.

Overall view.

Overall view.

Close up of the tensioner bolt, This uses an existing threaded hole on the unomog engine mount, probably there for just this type of purpost.

Close up of the tensioner bolt, This uses an existing threaded hole on the unomog engine mount, probably there for just this type of purpost.

View from above

View from above

View with the belt fitted.

View with the belt fitted.

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