NX300H fuse locations

Andy Basingstoke · September 30, 2018

I have a NX300H which until recently, provided 13v to the caravan fridge pin 10 on my 13 pin towing socket. We had an issue with the caravan cable and had to replace it, since then no power has been measured as present on this pin. I have tried looking everywhere for a fuse layout to check if this is the issue and cannot find anything. I spoke to the local Lexus dealer who quoted me over £200 to investigate!. I declined. Can anyone help please?

Rutlandlex · October 3, 2018

Are you saying that there is no power coming out of the pin on the car since having the caravan cable changed? The 2 should be unrelated. Have you checked the socket using a multimeter and are you sure that you're checking the right pin? You can download and print out a 13-pin pin-out diagram from the Internet but just be aware that sometimes they are designed for the installers who are wiring the sockets from the back and therefore the pin-outs are sometimes the reverse of how you would look at it from the outside. The fuses are normally under the boot floor where the towbar wiring is.

Andy Basingstoke · October 4, 2018

Hi Neil,

I had an issue with the cable and had to change it. Prior to the change, the fridge in the caravan would work and the Battery system would charge the caravan Battery when connected to the car. Since the change, neither now work. I have found the 13 pin diagram and can confirm pin 10 is what I am checking. This should be 0v with the ignition off, and about 14v when on. I have measured it in both circumstances and found the voltage to be 0v in both cases. I have checked the in line fuses that are connected directly to the Battery, which would potentially indicate that these were added after the initial build of he vehicle. These seem to be fine.

Rutlandlex · October 11, 2018

Hi Andy,

When you say ignition on do you mean the car is in Ready mode? Do you get 12-14V on the wire before the fuse and after the fuse inside the back of the car? If you do get a correct voltage there but not at the socket then there could be a wiring fault inside the socket or the socket could be faulty. Are you definitely checking pin 10? The reason I ask is that most pinout diagrams on the Internet are displayed from the point of view of the installer who is wiring from the back of the socket whereas you are looking at the front of the socket so therefore the pins are reversed left to right. The opposing pin to the fridge is for the brake lights so you would get zero volts on that even with the engine running unless someone had their foot on the brake pedal.

This article is the best for diagnosing as it shows the pinouts from your perspective i.e. the front of the socket: https://caravanchronicles.com/guides/13-pin-socket-basic-fault-finding/

Andy Basingstoke · October 14, 2018

Hi Neil

Issue resolved. I ended up having to take it to the engineer who services the car. He did say to me to check the fuses in the boot which were added to the Battery after manufacturing. This was the very first step I took. The pin layout I have checked and also it is printed on the cover of the socket, so I was pretty confident of the layout. Having checked the fuses on the Battery with no success, I ended up checking every other fuse in the engine bay, of which there were many!! Still no success, so a visit to Gary. After an hour he came back and found the issue. He managed to trace the cabling of the socket (something I was not able to do) and found the connections added at install. He then checked all the fuses and found one was actually missing. When he fitted this, the power was found to switch to the pin when the ignition was on. Now this was confusing, as I believed I had this before the cable change on the caravan. AS the cable was changed independent of the car, I cannot say it was removed when the did the work. All I can now assume, is the power was never there in the first place. Gary charged me a 1/3 of what Lexus were offering. As a note, I did contact Lexus in Reading and explain the circumstances and received a response.

Thank you for your email

I have checked in to the tow bar fitment on you NX300h and can see it was fitted back in October 2016, we would have advised that as the tow bar was fitted two years ago that there would be an initial diagnosis charge of £185 + vat, if at this time we found that the fault was due to the original fitting of the unit we would have corrected the fault with no charge to yourself, as you declined this and the fault has been corrected by a third party I am sorry to inform you that we do not cover the costs of any third party repairs

Kind regards

The only advise at the time of speaking to Lexus was to offer to investigate at a fee of £185+vat. Nothing about FOC if found to be their mistake. I wonder also if they would have "found" the same issue. One will never know.

Thank you for your responses and help Neil, it was appreciated.

Andy

Rutlandlex · October 23, 2018

Hi Andy,

You're welcome. Glad you got it sorted. I'm very dubious about whether the dealer would have admitted to such a mistake and I don't like the concept of getting the repair done for free based purely on their honesty. They could easily have said that someone had removed the fuse after fitting so therefore not their fault oh and here's a nice big bill for us to put it right!

Happy caravanning with a cold fridge 😃