Tow car behind motorhome how to get car's tail lights wired?

[nehuge]

I have a motorhome from 1995 with a Ford chassis underneath. I'd like to tow our car behind it, 2007 Honda CRV. I have hooked up the 7 pin trailer connector on the back of the RV and also a 6 pin on front of the car. Ran wires through the car to the back.

My RV had four wires/pins on its old hitch 1) right/brake (stop) 2) left/brake (stop) 3) tail lights (markers) 4) ground. I upgraded it to a 7 pin so that I have reverse lights if need be and a dedicated power wire to charge the car's battery on the fly.

Got it wired correctly, and my car is the type with red brake bulbs and markers, but separate amber bulbs.
I'd like it to work where the ambers flash just like when the car is driving alone. I bought this tail light converter which is called a "2 to 3 wire" converter. The converter on one side call input has 3 wires called "left/brake", "right/brake" and ground. The output side has "left", "right" and "brake. I thought I hooked it up correctly but it acts strangely. The amber turn signals work, but as soon as I touch the brakes on the RV, the dash/instrument lights on the RV light up. I thought this was backfeed but still acted that way after putting a diode in. Even putting the hazards on in the RV only makes the 'red' bulbs on my car flash but the kinda double flash and the RV instrument panel again flashes with it.

Anybody have a way to wire this wire by wire, in detail to where I can see what I am doing wrong?

 

[rjenkinsgb]

In the car, both side brake lights will be wired together.
Likewise both tail lights, with the same feed for those operating the instrument lights, from the sound of it.

Does the car have separate lamp filaments for tail & brake? I'm familiar with UK wiring but not that sure of the US wiring..


Edit: Found an article that includes the relevant wiring diagrams for a 2006 CR-V:

Brake Lights Not Working?: 3 of the 5 Brake Lights Will Not Work ...

3 of the 5 brake lights will not work when I compress the brake. They do however light up when I turn the headlights on but when I hit the brake only...

www.2carpros.com

According to that, they have twin filament lamps for separate tail and brake wiring, in addition to the separate indicators.

Also, front and rear indicator and side (marker) lights will presumably be linked so the converter will be running two or more bulbs on each output.

From the description, you may have the converter "brake" output connected to the tail lights rather than brake lights??
If that diagram is correct and it uses separate lamp filaments, only the tail lights could backfeed to the cluster?

 

[Diver300]

The converter ground, the RV ground and the car ground all have to be connected together.

On the converter, the "left/brake" and the "right/brake" are inputs have to be connected to those lights on the back of the RV. The "left", "right" and "brake" are outputs that have to be connected to the indicators and the brake light on the car.

It is worth checking that there is no problem lighting the car indicators and brake light from a 12 V feed when the car is in the state it would normally be when being towed.

The tail lights, ignition feed and reversing light will correct directly from the RV to the car without any connection to the trailer.

The hazards on the RV may not work with the 2 to 3 wire converter.

On a 2 to 3 wire converter, some behaviour depends on what was happening before. When both lights turn on at the same time that could either be the brakes coming on or the hazards starting a flash, and the converter may not know which is correct.

The inputs that the 2 to 3 wire converter sees are like this:-
Both off. No braking or indicating.
Both on. Braking, or braking and indicating during the illuminated phase of the indicator flashing.
One on. One side indicating, or the braking and the other side indicating during the off phase of the indicator flashing.

The converter has to work out what to do depending on what happened before. Trying to include hazard light operation as well would be very difficult.

 

[nehuge]

In the car, both side brake lights will be wired together. You mean I should wire them together, or you're saying from factory they should already be wired together?
Likewise both tail lights, with the same feed for those operating the instrument lights, from the sound of it. Probably

Does the car have separate lamp filaments for tail & brake? I'm familiar with UK wiring but not that sure of the US wiring.. The car has two red bulbs on each side. The top red bulb is a small single filament bulb. The bottom red bulb is a larger bulb with two filaments. Top one is marker, bottom one is a "second" marker on one of its filaments, and the brake/stop light on the other filament.


Edit: Found an article that includes the relevant wiring diagrams for a 2006 CR-V:

Brake Lights Not Working?: 3 of the 5 Brake Lights Will Not Work ...

3 of the 5 brake lights will not work when I compress the brake. They do however light up when I turn the headlights on but when I hit the brake only...

www.2carpros.com

According to that, they have twin filament lamps for separate tail and brake wiring, in addition to the separate indicators. ok

Also, front and rear indicator and side (marker) lights will presumably be linked so the converter will be running two or more bulbs on each output. ok

From the description, you may have the converter "brake" output connected to the tail lights rather than brake lights?? I'll check and report back
If that diagram is correct and it uses separate lamp filaments, only the tail lights could backfeed to the cluster? I'll check and report back

 

[nehuge]

The converter ground, the RV ground and the car ground all have to be connected together. Yes, I wired it to the 7 pin connector on the RV hitch, it goes to the 6 pin connector on the car, and that goes straight to the car's negative battery post.

On the converter, the "left/brake" and the "right/brake" are inputs have to be connected to those lights on the back of the RV. The "left", "right" and "brake" are outputs that have to be connected to the indicators and the brake light on the car. I have the yellow left/brake, the green right/brake, and the brown taillight/marker wires from the 7 pin connector on the RV go to the 6 pin connector on the car, and it turn those yellow and green and brown wires go to the rear of the car by the tail light. The

"left", "right" and "brake" outputs are those I think I get stumped on.

It is worth checking that there is no problem lighting the car indicators and brake light from a 12 V feed when the car is in the state it would normally be when being towed. Yes I have put power to each pin on the front of the 6 pin car connector and I can get all bulbs on the car to light up that way.

The tail lights, ignition feed and reversing light will correct directly from the RV to the car without any connection to the trailer. Yes, I have the brown 'tail/marker' wire from the 6 pin connector on the car going all the way through the car to the back and have "tee'd" it into the appropriate wire on the OEM/factory car wiring.

The hazards on the RV may not work with the 2 to 3 wire converter. Hmm

On a 2 to 3 wire converter, some behaviour depends on what was happening before. When both lights turn on at the same time that could either be the brakes coming on or the hazards starting a flash, and the converter may not know which is correct. Hmm

The inputs that the 2 to 3 wire converter sees are like this:-
Both off. No braking or indicating. Noted
Both on. Braking, or braking and indicating during the illuminated phase of the indicator flashing. Noted
One on. One side indicating, or the braking and the other side indicating during the off phase of the indicator flashing. Noted

The converter has to work out what to do depending on what happened before. Trying to include hazard light operation as well would be very difficult. Noted

 

[rjenkinsgb]

You mean I should wire them together, or you're saying from factory they should already be wired together?

It sounds like the diagram is correct, so both sides will be linked together within the existing car wiring.

I'll wait for you to check which lamps the converter brake light output is connected to?

 

[Diver300]

I'm not sure where the connectors are and it doesn't really matter. The connectors are there so that you can separate the car from the RV, but the connections will be the same wherever the connectors are positioned.

The 2 to 3 wire converter is expecting a ground that is connected to the RV ground and the car ground. Make sure that the grounds do connect together when the car is joined to the RV.

I suggest you get a bulb and connect one end to ground. Connect the other end to a connection on the RV and check that it causes the bulb to come on when the RV brakes are applied, and that causes the bulb to flash when indicating left and does nothing when indicating right. That connection needs to go to the "Left/brake" input on the 2 to 3 wire converter.

Similarly, find a connection on the RV that causes that bulb to come on when the RV brakes are applied, and that causes the bulb to flash when indicating right and does nothing when indicating left. That connection needs to go to the "Right/brake" input on the 2 to 3 wire converter.

On the car, find the wire that causes the left rear indicator to light when 12 V is applied to it. The left front and left side repeater indicators may light, they may not, it doesn't matter. That wire is connected to the "left" output of the 2 to 3 wire converter.

On the car, find the wire that causes the right rear indicator to light when 12 V is applied. The right front and right side repeater indicators may light, they may not, it doesn't matter. That wire is connected to the "right" output of the 2 to 3 wire converter.

On the car, find the wire that makes all three brake illuminate when 12 V is applied. If only one or two illuminate, find all the wires needed to illuminate the three brake lights, and put diodes on each one, with the cathodes connected to each wire, and join all the anodes together. If there was only one wire, don't bother with diodes and connect the wire that illuminates the brake lights to the "brake" output of the 2 - 3 wire converter. If there was more than one wire, connect all the anodes to the "brake" output of the 2 - 3 wire converter.

I hope this helps.

If you are still stuck, post some photos and diagrams.

 

[nehuge]

I'm not sure where the connectors are and it doesn't really matter. The connectors are there so that you can separate the car from the RV, but the connections will be the same wherever the connectors are positioned.

The 2 to 3 wire converter is expecting a ground that is connected to the RV ground and the car ground. Make sure that the grounds do connect together when the car is joined to the RV.

I suggest you get a bulb and connect one end to ground. Connect the other end to a connection on the RV and check that it causes the bulb to come on when the RV brakes are applied, and that causes the bulb to flash when indicating left and does nothing when indicating right. That connection needs to go to the "Left/brake" input on the 2 to 3 wire converter.

Similarly, find a connection on the RV that causes that bulb to come on when the RV brakes are applied, and that causes the bulb to flash when indicating right and does nothing when indicating left. That connection needs to go to the "Right/brake" input on the 2 to 3 wire converter.

On the car, find the wire that causes the left rear indicator to light when 12 V is applied to it. The left front and left side repeater indicators may light, they may not, it doesn't matter. That wire is connected to the "left" output of the 2 to 3 wire converter.

On the car, find the wire that causes the right rear indicator to light when 12 V is applied. The right front and right side repeater indicators may light, they may not, it doesn't matter. That wire is connected to the "right" output of the 2 to 3 wire converter.

On the car, find the wire that makes all three brake illuminate when 12 V is applied. If only one or two illuminate, find all the wires needed to illuminate the three brake lights, and put diodes on each one, with the cathodes connected to each wire, and join all the anodes together. If there was only one wire, don't bother with diodes and connect the wire that illuminates the brake lights to the "brake" output of the 2 - 3 wire converter. If there was more than one wire, connect all the anodes to the "brake" output of the 2 - 3 wire converter.

I hope this helps.

If you are still stuck, post some photos and diagrams.

I'll check this out this weekend if the rains let up!

 

[shokjok]

Your location unknown, most jurisdictions would forbid towed vehicle tail lights from being interfaced to the towing vehicle. To avoid this anomaly, follow tow truck operator's practices and use separate magnetic tow lights on each rear corner on the roof or deck lid.
If a tow dolly or trailer isn't used, the towed vehicle will be unusable.

 

[Diver300]

Nehuge is from the USA, it says so in his profile.

In most places, when a vehicle is being towed as a trailer, then the rules about trailer lights apply. It's standard practice to run the towed vehicle lights from the towing vehicle, as would happen when a trailer is towed.

As long at the towed vehicle lights revert to normal operation when the towed vehicle is being driven on its own, there is no problem.

 

[shokjok]

If you are able to post a video of your situation, we can better help you to be on your way.