Thread: LED trailers

Originally Posted by imaz

This video used small resisters? But obviously she added more than we would need into the 7 flat.

LED trailer plug resistor wiring - YouTube

Putting aside the watts/ohm of the resistors, why splice and solder into the white/ground wire and not just attach at the screw terminal as she has done at the other end of each resistor?

I am thinking of adding a 50w/6ohm resistor into a 7-pin flat to 7-pin round adapter and cannot think why it would not be simpler to just attach the resistor via the screw terminals.

Originally Posted by iannicki

Putting aside the watts/ohm of the resistors, why splice and solder into the white/ground wire and not just attach at the screw terminal as she has done at the other end of each resistor?

I am thinking of adding a 50w/6ohm resistor into a 7-pin flat to 7-pin round adapter and cannot think why it would not be simpler to just attach the resistor via the screw terminals.

Because the resisters are relatively large and they do get very hot. Even the way I have done it below, I’m sceptical if it’s safe for the surrounding wires. Although it works, and it’s only the indicator circuit that the resisters heat up - I may end up just putting resistors to my camper trailer tail lights, mounting the resisters externally. Just not sure if the resisters in use are water resistant??

That’s why when I build mine I use thermal adhesive to mount the resistors to the case and turn it into a heat sink.

The higher the power handling of the resistor the better they tend to dissipate the heat generated.
I’m confident mine will be fine, if I get too concerned I’d look at potting them in thermal epoxy.

My in-line version like you’ve built was used for the last 10 years without a problem using the resistors I linked above.

The internal install version only differs in how it’s wired to the vehicle in my application.

Originally Posted by Tombie

That’s why when I build mine I use thermal adhesive to mount the resistors to the case and turn it into a heat sink.

The higher the power handling of the resistor the better they tend to dissipate the heat generated.
I’m confident mine will be fine, if I get too concerned I’d look at potting them in thermal epoxy.

My in-line version like you’ve built was used for the last 10 years without a problem using the resistors I linked above.

The internal install version only differs in how it’s wired to the vehicle in my application.

So despite the indicator is not always on, is the indicator circuit constantly probed, even though the trailer symbol is not continuously lit?

Originally Posted by imaz

...is the indicator circuit constantly probed, even though the trailer symbol is not continuously lit?

On a D3 they are constantly probed, which is why LED trailer lights flicker when hitched to a D3 unless other precautions are taken.

However, the D4 is different, they are only probed once, whenever specific events occur - the opening or closing doors (possibly some other events as well, I'm unsure).

So for a D4 heating of the resistors is not much of an issue during the normal course of indicator use - ie on for a few seconds to indicate a turn and then cancelled. The heat issue will most commonly arise when you leave your indicators running continuously, typically when the hazard lights are turned on.

And a further silly query regarding resistors etc! At least the answer/s should be simple

Am I right in assuming the heat sink is only required when the indicators are activated either by turn signal or hazard lights (D4 MY16)?

Also, having followed Kelvo's advice/suggested items, are the 25W 6.8 Ohm resistors the best sizes for fitment?
Like others, I plan to fit the pair in the LHS rear wiring hideaway where some of the tow equipment usually resides.

Originally Posted by gavinwibrow

And a further silly query regarding resistors etc! At least the answer/s should be simple

Am I right in assuming the heat sink is only required when the indicators are activated either by turn signal or hazard lights (D4 MY16)?

Also, having followed Kelvo's advice/suggested items, are the 25W 6.8 Ohm resistors the best sizes for fitment?
Like others, I plan to fit the pair in the LHS rear wiring hideaway where some of the tow equipment usually resides.

Yes and yes

Heat only generated when indicators are flashing.
25w 6.8 Ohm are perfect.