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12 volt starting conversion on a 1997 24 valve manual 80 series LandCruiser


Well-Known Member
Nov 18, 2010
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80 series LandCruisers in this part of the world got a 24 volt starter motor to make starting easier in cold weather. This necessitates the use of two 12 volt batteries because the rest of the vehicle's electrics is 12 volt. A switchover relay is used to give the starter 24 volts.

I am preparing my 80 for travel in Africa. I will be sleeping in a roof tent, cooking, using a fridge and various other electrical items when I'm stopped (battery not charging) and need a leisure battery for that purpose. Now, because both battery positions are taken up by the need for 24 volt starting, it means that a leisure battery must be located somewhere in the back of the vehicle. Lots of people do this but it wasn't for me. Plenty have successfully done the conversion and I decided to give it a go too.

So, the only reason I'm doing this conversion is to free up one battery position for use by the leisure battery. The 24 volt starting system was not giving me any trouble but I really didn't want a third battery in the back of my LandCruiser and there should be no problem starting on a 12volt 2.5kw starter. I'm in Ireland and it doesn't get cold enough here to cause starting problems. I sourced the 12 volt starter new on Australian eBay and even with shipping (which took two months by sea) it wasn't prohibitively expensive.

I got some information on a couple of LandCruiser forums but I haven't been able to find a detailed account and I'm hoping those who find this thread and are thinking of doing the conversion will benefit from my experience.

When reading driver side (DS) and passenger side (PS) you should be aware that this is a RHD vehicle.

Here's a synopsis of what I have accomplished after completing the conversion....

  • The PS battery now does everything that both batteries did before the conversion.
  • I have completely removed the 12v-24v switchover relay and associated cables.
  • The fusible links connected to the DS battery were moved to a junction box and the junction box has been brought across to the PS battery with 25 mm sq cable.
  • The starter has been replaced with a 12 volt starter.

Ok, let's start. Here's a photo before anything was done....


The switchover relay is located behind the PS battery....


Here's a picture with the cover removed. The entire relay as you see here will be removed along with every cable you see connected to it....


Here is a close up of the switchover relay. You can just see a junction box that is marked "Battery +B". The power cable running from the PS battery to the starter goes through that junction box. The reason the junction box is there is to take a connection from the switchover relay also. This short cable will be removed and the junction box and power cable from the battery to the starter will be left in place.


Here is a close up of the junction box....


and now a close up of the opened junction box showing the two cables....


In case you're not sure where the starter motor is. Here it is just below the oil filter on the PS....


After taking off the 24 volt starter motor I realised that the trigger terminal was different to my new 12 volt starter....


The old 24 volt motor has a male spade connector inside an housing....


The new 12 volt starter has a bare screw to hold a lug. I made up an adapter cable to connect it to the loom....


There are a few fusible links connected to the DS battery that need to be brought over to the PS battery. I thought the best way to do this was via a junction box which will be brought over to the PS battery....


Here's the new junction box mounted to the side of the DS battery housing and the fusible links still connected to the DS battery....


and now the fusible links moved down to the new junction box and 25 mm sq cable in place and housed in the standard convoluted tubing running across the top of the radiator....


That convoluted tubing is big and there was plenty of room for the new cable in it....


Rather than going directly to the positive terminal of the PS battery with the cable carrying the fusible links what better place to go than the now free terminal in the "Battery +B" junction box.


The negative terminal of the PS battery used to run into the switchover relay, this was completely removed. A separate earth ran from the switchover relay to the engine, this was disconnected from the switchover relay, a new earth cable was installed from the negative pole on the PS battery to a cleaned up bolt hole on the chassis and the engine earth mentioned earlier was also bolted here.

Having fitted the new starter motor, connected it up, run the fusible links across, removed the switchover relay, removed the DS battery, fitted the new negative cable from PS battery to chassis to engine it was time to look over and double check everything....

....all looked well so it was time to give it a go. Switched on ignition, everything ok, turned it to the start position - NOTHING. Sh1t, sh1t, sh1t. Switch off, run around, have a smell
, nothing burning
. Check everything again, all ok. Got an helper to turn key to start position while I lay underneath with a voltmeter on the trigger switch on the starter - NOTHING.

:Admin Note: See post 45 here for how to resolve this problem without adding an earth wire.

I reckoned I had inadvertently removed an earth somewhere and the most likely place to have lost earth was the starter relay. I had a look at the wiring diagram and determined that I needed to add an earth to the white with red stripe wire going into the starter relay.


I peeled it back, brought a temporary earth jumper cable to it and it started just as it always did, instantly, no change, no different sound, just as normal.

I soldered the new earth cable, re insulated it and put the starter relay back in place....

The starter relay is located in the engine bay PS back towards bulkhead.


I have gone on and fitted a split charge system and run cables around the vehicle to fuse boxes in various places in the vehicle.
Here's a link to the 12-24 volts switchover system wiring diagram.... Volts Switchover System.pdf

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I did a write up on the 'MUD' forum a few years back when I did mine. No decent pictures though, I also used the HDJ 100 starter which needed modifying to fit, nice post.

Welcome to the dark side :icon-biggrin:,


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I left the fusible links connected to the DS battery on my set up. That way all the PS battery does is crank. There are no other drains on it. If the DS battery went flat - say I left my lights on or something, then it's only the solenoid that would need power and I could effectively do that with a jump lead from the PS battery to the DS battery

Nice write up. Strangely I seem to remember jumping the changeover relay timer in the footwell. Don't remember why now.
@Chris, some have disconnected the plug and jumped the connector, I did not bother touching that at all.

I too have any and all parasitic draw taken (Alarm/clock etc) from the right battery, left battery used only for cranking. I use the blue sea's dual sense unit. If my car is left for three or four days the unit will uncouple the batteries, my thinking is always protect the starter battery. There is an override button on the centre console, OFF/AUTO/ON, using that I can split or force the batteries together, TBH it is normally left in AUTO, I get in after the car has stood for a week and just crank and away we go, once the unit detects high enough voltage on the starter battery (alternator direct to starter battery), and normally after about 15 seconds the batteries couple up again. I do have a solar panel used when camping (fridge/lights and so forth), this is connected to the right battery, and again the splitter is 'dual sense' so it detects the moment any battery is charged and so I can charge from right to left and vice verse, of course the batteries never get low enough to uncouple with the panel in the sun but, if the rack is left on with the panel in the underground garage with minimal light through the fume vents they will uncouple again after a few days.

May be having a rethink on moving the alternator link direct to the right battery to reduce voltage drop?


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What a great write up and to hear the other options/approaches. Love this forum.
Brilliant write up.

Hi ive had my 12v starter sat around for ages as i find wiring a bit daunting to be honest.
I have printed your whole thread to use as a guide when i finally do the conversion next week.
I think i have it but ive a few questions i hope you can answer, just so i dont fry my car or my brain.

Thanks in advance. extra wire.jpg
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I kept all my original wiring and batteries in place and the 24v motor in the back just in case I need to revert. A 15 minute job. I manually alternate the cables on the batteries to keep both charged. The reason I converted was just for a little more reliability and to have a spare battery in case one went flat. Been caught out now 3 times with 24v battery failure and no available back up.
Great write up ... this is on my list as well.

Just realised this is an old thread but I had not seen it before :)

That was the cable connecting the ds battery to the 12v-24v switchover relay. The rest of the description is in the photo above. Click on "View attachment 33011".

First photo below is where it was, on the change over relay red arrow.

The second photo is where it eventually ended up. Just about in the same physical position but now as the feed from the split charge relay back over to the ds battery, once again red arrow. I used the space vacated by the switch over relay to put the split charge relay and that cable sat perfectly onto it.

switch_over_relay.jpg split_charge_relay.jpg
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Thanks I have it now :)

It really is a great write up. Thanks for taking the time to take the pictures and make the notes.
Although an oldish thread, it is excellent not only for potential doers, but for explaining the basic set up and the conversion.

I'm never going to be an auto electrickery person, but even I feel I've gleaned some knowledge from this thread.

First-Class presentation Garfieldus and due credit to the other contributors :dance:

(If only I hadn't invested megabucks in a new 24V starter, a few years ago...:doh:)
Using a jumper on the connection in the passenger footwell provides the 0v needed for the starter relay so saves cutting into the harness and soldering a new wire in.
I've made a little folder with pictures so the next owner can convert back if needed.
Ok, let's start. Here's a photo before anything was done....

A fantastic guide there Mr F, many thanks...... I missed this when you posted it.

The 12v starters used to be available from Wood Autos, but seem to be order only now, does anyone know of another supplier?
Ebay Aus have them very week but the shipping makes them pricy, IIRC the warranty is pretty good though.

Free courier


If you'd like to buy one on the Kiwi version of Ebay "Trademe" The price is Kiwi dollars so thats about 110 quid.

I will happily bring it over for you, for no charge whatsoever. Most you'll have to do is hang on a bit and meet me at Manchester airport.

Youve missed the boat for this trip but i think i could get one to you for mid to late March.

A fantastic guide there Mr F, many thanks...... I missed this when you posted it.

The 12v starters used to be available from Wood Autos, but seem to be order only now, does anyone know of another supplier?
Whoops further thought reminds me it was a real faff on getting a trademe account so i bought mine using my girlfriends account.

Best thing to do would be to buy using Ebay from Australia and get them to ship it to me on the South Island and ill bring it back to blighty.


If you'd like to buy one on the Kiwi version of Ebay "Trademe" The price is Kiwi dollars so thats about 110 quid.

I will happily bring it over for you, for no charge whatsoever. Most you'll have to do is hang on a bit and meet me at Manchester airport.

Youve missed the boat for this trip but i think i could get one to you for mid to late March.