Ford Ranger PX - LED trailer lights

Forums › Home Workshop DIY › Ford Ranger PX - LED trailer lights

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barrg0

8 posts

Wannabe Geek

#3129434 19-Sep-2023 15:22

MartinGZ:

I'm no electrical expert, but 120 Ohm seems plenty. As above, Ford state 500 mA current which implies a resistor of 24 Ohm at 12 VDC. I'd check:

Connection - is it actually the tail light wire you've hooked into.
Whether the resistor is actually as stated.
All your terminals are tight.
Does it work if you take that resistor out.
I actually left the resistor off the tail light circuit as I found it didn't need it. That circuit is tail lights, running lights, and rear camera on the caravan, so probably enough anyway.

HI Martin

The brown wire is the one for tail lights. Ive checked all the connections and they're fine. But where I hooked into the feed there is a black wire which I bypassed thinking that it isn't part of the light circuitry. I don't know what its for. Could this have something to do with my problem?

I'm using the same resistors you used and have checked it for resistance and is ok.

All terminals are nice and tight.

It does not work with the resistor out. The only way it will work is by using the ford adapter.

Unlike your setup, I left the resistor off the brake light because it has never been a problem.

Greg

MartinGZ

376 posts

Ultimate Geek
+1 received by user: 128

Subscriber

#3129543 19-Sep-2023 22:15

Without being there, difficult to help you. The only way you could check if it is the correct wire is check the voltage with the tail lights on. Take the resistor out and check that you have 12 VDC between your connection and earth. BTW, it has been known for wires to change colour where different looms are connected.

If you look at my earlier photo of the Ford adapter, those are 120 Ohm resistors, just a lot smaller power rating than the ones you are using. So the resistor should be fine, guess it comes back to connections.

barrg0

8 posts

Wannabe Geek

#3129694 20-Sep-2023 11:57

MartinGZ:

Without being there, difficult to help you. The only way you could check if it is the correct wire is check the voltage with the tail lights on. Take the resistor out and check that you have 12 VDC between your connection and earth. BTW, it has been known for wires to change colour where different looms are connected.

If you look at my earlier photo of the Ford adapter, those are 120 Ohm resistors, just a lot smaller power rating than the ones you are using. So the resistor should be fine, guess it comes back to connections.

Thanks for your reply Martin. The weather today is not very pleasant ATM so I thought Id upload a couple of photos of my setup just to make sure Ive done it correctly. My setup doesn't have the separate connector for the box like yours. I decided to piggy back the wires from the connector to the box to make it a one piece arrangement. Hope this is OK? These two connectors simply plug into the existing feed with mating connectors as shown in bottom photo. Hopefully I will be able to check the voltage between the connection and earth later today. I would dearly love to find a wiring schematic of my van to show the wiring colours etc. but no luck so far.

The piggy back connection.

The red brake wire was omitted because it works OK. Its the brown one I'm having issues with!!

Assembled in van.

barrg0

8 posts

Wannabe Geek

#3129754 20-Sep-2023 13:19

Update.
I’ve just checked the voltage at the brown wire in the box and it’s showing 11.7 volts with lights on.

MartinGZ

376 posts

Ultimate Geek
+1 received by user: 128

Subscriber

#3130293 21-Sep-2023 21:25

Not sure there is much more I can help you with as I'm not an electrical specialist. Perhaps someone else may be able to offer some thoughts?

I do note that the Ford adapter does use a resister across each of the feeds, perhaps their canbus needs some sort of feedback from each, so add a resistor to your brake lights? Clutching at straws here.

barrg0

8 posts

Wannabe Geek

#3130302 21-Sep-2023 22:07

You won’t believe this but that is exactly what I just did lol. So I now have the brake wire with resistor as well. Now that’s the only thing I haven’t tried yet. But yes I tried the Ford adapter again today and it all works perfectly. So I’m hoping like you that maybe Ford in their crazy wisdom have a weird way of wiring the ranger. Fingers crossed. It’s too late now so I’ll try it out in the morning and let you know how it went. Cheers

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barrg0

8 posts

Wannabe Geek

#3130609 22-Sep-2023 19:08

Hi Martin
Well I fitted the box to the van again this morning with all four feeds running through resistors and wouldn’t you know it…….Voila!!!!!!! It works. So it was definitely the omission of the brake resistor that was causing all the headaches. As unstitched was something as simple as that in retrospect. So thanks for all your input in getting this to work Martin I really appreciate it. Great work. Cheers

barrg0

8 posts

Wannabe Geek

#3130931 23-Sep-2023 12:10

barrg0: Hi Martin
Well I fitted the box to the van again this morning with all four feeds running through resistors and wouldn’t you know it……. Voila!!!!!!! It works. So it was definitely the omission of the brake resistor that was causing all the headaches. As usual it was something as simple as that in retrospect. So thanks for all your input in getting this to work Martin I really appreciate it. Great work. Cheers

MartinGZ

376 posts

Ultimate Geek
+1 received by user: 128

Subscriber

#3130948 23-Sep-2023 13:27

Glad it worked Greg. The Ford trailer electrics with CAN Bus has had years of criticism, but it is what it is. Fairly easy to solve if we need too.

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