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Hi hilux experts,

Was going to replace the ALT-S fuse in the 2015 N80 GUN126R SR5 hilux but on looking even though the fuse box cover shows it as being there, it actually isn't. No wiring to it either. Asked the local Toyota mechanics and they said it doesn't have one. I find that odd myself as I understand it is a temperature sensing alternator by all accounts.

I am trying to get a higher voltage to the dual AGM battery by installing those fuses that trick the alternator into delivering a slightly higher voltage. The redarc bcdc is ok but the AGM second battery is not being provided enough volts to charge it adequately once the car temperature is up.

Anyone else know where that ALT-S fuse on this model Hilux is? Does it really not have one?

no it doesnt have one , the alternator is 100% canbus controlled and a variable voltage type. Ive tried to get more juice out of it with no luck - with a scantool plugged in and forcing maximum pulse width the volts only go up to 13.9v and no higher.
once out of warranty i may pull it apart and install an external regulator but dont know if the canbus will chuck a hissy fit

Thanks for verifying numberplate.

I like your thinking - maybe even install an aftermarket alternator that suits this model.

This causing some grief as the dual battery system is largely not being able to work because it never gets a voltage high enough to charge. I'm always needing to plug into a charger to boost it to keep the fridge going in the rear. Painful.

There must be a better way!

Sell the AGM and fit a good lead acid deep discharge.

Is it a redarc LV. They should work as low as 9 volts.

I would monitor how your system is operating. And checking it’s set up correctly(is the bcdc set to a AGM Battery?) and checking it’s operating correctly (Boost, Absorption,Float)
Redarc BCDC’s step up the Voltage to get the charge in. My main is generally at 13.2-8 while the second in boost is around 14.5
Are All connections of good quality and little to no resistance/voltage drop in the lines.

I have a deep cycle lead acid 105Ah and don’t have any problems to speak of. And I only drive 15 min each way for work. Battery is always in float by the time I get home. Fridge is only on when camping groceries etc. just all the little things drawing in the car constantly.


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I also run a 105Ah lead acid aux battery, but there is no real need for a dc-dc converter if you run a solar panel. I use a Projecta dual battery setup with the aux battery and Projecta under the bonnet. In the back there is an Engel 40L fridge that runs 24/7 and a Victron 75/15 solar regulator. I have a 110W mono solar panel on the canopy roof, you can’t even see it unless you look down on it. If the ute is parked in the shed more than overnight I plug the Engel into 240V. The trick is to use a regulator (or if you must a dc-dc converter) with a load output and a battery output, you don’t want your fridge and aux battery in parallel all the time. The Victron you can up the battery output voltage so when the panel is in the sun the battery gets a correct charge profile for the type of battery. When the engine is running it of course gets alternator charge as the Projecta parallels the batteries. Even in winter the panel charge plus the 30min drive to work and back keeps the aux battery fully charged.