3rd Brake Light On Toad

[Gil_Johnson]

Ed,

There is an off the shelf option.  Get a 2 wire to 3 wire converter for about $20.  These are indended for vehicles with separate stop and turn bulbs, but eould work fine to operate the 3rd brake light.

Just an option,

Gil

[Edward Buker]

Thanks Gil,

Not sure that converter will work. My coach uses turn and brake together on the same two wire portion of the harness (same bulb filament on the coach end for brake and turn). The car is set up the same way, as adapted for toad,  using  just one bulb filament for turn and stop lights. Maybe you are implying that you can use these converters in reverse mode and take a two wire feed and make a 3 wire at what would be the trailer end (toad end).

 Most of these parts were in my junk box and sometimes it is more fun to get the soldering iron out try and solve these problems for yourself. We will see where that leads...

Later Ed

[Gil_Johnson]

Ed,

Yes this converter will work.  Another pulser choice that is weather resistant is the "back-off" it's made by Signal Dymanics.

Just another choice,

Gil

[Dick Simonis]

On the subject of toad brake lights....why are diodes needed at all?  I have them but fail to understand what the problem is if the toad brake lights operate in parralel with the coach.  Back feed has been mentioned but I still do't quite get it.....what am I missing???

[Edward Buker]

Thanks Gil. That pulse module looks like a good design being weather sealed. The unit I bought is designed to go into a tight space on the convertible top where the third brake light is housed. Glad we can link this additional module option here. I think for most vehicles it is a better designed unit.

 I hitched my Mini up to the coach yesterday to check out receiver to vehicle mounting offset and test the lights. It all worked well but in daylight the lights really were not very bright so the led 3rd light pulsed mode should be a big help. I have never measured the voltage at the toad brake light but there is a lot of wire and contacts between the brake switch in the RV and the tail light of the toad plus the added diodes in many cases. My opinion is that many folks should consider this feature if there is any question about the brightness of the brake light set up on the toad. It is very cheap insurance to avoid a lot of pain on the road. I've noticed that red vehicles, in particular, brake lights can be harder to spot when on. My Mini being burnt orange seems to have the brake lights blend in with less contrast also.

 Thanks for the converter info. I did not know that they would work in reverse mode...never played with one but this would make things easier than my circuit for most folks.

Looks like I need to incorperate a dropped reciever given I have a 6 inch height offset from coach to car. Not overly thrilled about adding that unit....

http://signaldynamics.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=40&category_id=14&option=com_virtuemart&Itemid=77&vmcchk=1&Itemid=77

Later Ed

[Gerald Farris]

Dick,
Yes, diodes are used to prevent feedback from the coach brake light system into the toad brake light system. If you are towing a 1950 Ford, you do not need diodes. However, if you are towing a modern car that runs the brake light circuit through a body computer, they are a must have.

In fact I installed separate bulbs in the rear taillight housings on my Jeep Grand Cherokee and did not run the toad brake lights into the Jeep brake light circuit. The reason for doing this is that the Jeep has a "bulb out" function in the body computer to warn of a burned out bulb that will malfunction if you install diodes in the circuit.

Gerald

[Edward Buker]

Dick,

 The diodes isolate the current so it can only go in the direction of the light filament and not back into the alternate wiring harness coming from the motorhome or the car when one of those sources is active with the brakes on.  You want all the current going to the bulb and because cars and electronics can vary so much you never know for sure what will happen if you back feed a harness. This is much like a check valve in plumbing....

Later Ed

[Dick Simonis]

Thanks for the info.  My GC is a '97 and I did have the diodes installed when it was wired for towing but did not install the relay on the brake light swhitch....partly because I couldn't find the switch.  When my Even Brake remote crapped out I simply ran without supplemental braking but now I'm installing a Ready Brake and have been wondering about the "back feed" and if it's an actaul issue.

My first plan is to change the brake light power so they don't activate unless the key is on which would solve the problem, if there is one.  Next might be to pull the brake light fuse.

Now I'm also thinking about the 3rd light.

Gotta deal with this pretty quickly as time is running ticking by before we head out for the summer.  Reckon I need to stop playing golf and attend to "stuff".

Dick

[Edward Buker]

Dick,

Not sure if I fully understand the relay on the brake light switch.....The diodes are sufficient for eliminating the feedback. There is no need to pull a fuse with the ignition on unless there is an active circuit in the car that drains the battery too quickly like some of the modern Nav systems or climate control. You should not need a relay on the brake light switch if the diodes are in place. It would just mean that your bulbs are getting powered from two sources, both the motorhome harness to the car if active, as well as the car brake light circuit being actived from a Ready Brake or equivalent actuator. The current feedback is still isolated by the diodes. There may be something I have not thought of here but on first pass this seems O.K.....

In the circuit I attached in my post, the relays are not primarily used to isolate, they are just logic setting. They allow the third brake light to be active only when both turn lights are active on the toad. You do not need these relays normally, just specific to the third brake light feature addition. Hope this helps.

Later Ed

[Dick Simonis]

Ed, that's what I thought but, for example, Roadmaster has  relay accessory for cars that have active brake lights when the ign key is off.  In their literature they refer to a feed back that can occur when the brake lights are illuminated from both sources and I can't figure out where the problem might be.  Like you, I just sort of figured the two 12 sources would merely be in parallel and no big deal.

Unless the concern is a feed back to the motor home brake circuit but again....can see the problem as the motor home 12v should be ~13.6 with the engine running and the diodes would/should block any leakage current to the toad.

I just may call Yardmaster tomorrow and see what is their logic

[Gil_Johnson]

Ed, the 3 to 2 converter will not work in reverse.  You need a 2 to 3 wire converter.

Dick, don't worry about both 12V sources lighting the brake light.  Make sure you do have diodes installed to prevent voltage attempting to go where it's not suppose to be.  In your case also make sure you have a charge line to your TOAD to power the supplemental brake system and maintain the TOADs battery.

Gil

[Edward Buker]

Gil,

I do not need a 2 to 3 wire converter (but thanks for the info anyway) I have some relays and diodes in my junk box. Always fun to draw something up and build it, especially when you are retired and don't have to.  

Later Ed

[Edward Buker]

Seems that I could not delete the existing diagram from my original post so I have included it here. I have added a diode to the third brake light feed coming from the relays to block any current backfeed. I also thought that it is simpler to obtain 12V power for the 3rd brake light input from the motorhome by using either one of the brake and tail wires as a power source. In that case you can omit the fuse if you do not feed 12V from the battery or another 12V toad source. Simpler is better....

later Ed

[Edward Buker]

I just wanted to pass along that the third brake light circuit that I provided works well and does add a good margin of safety over just the standard brake lights when towing the toad. The blinking 3rd brake light feature is available while driving or towing the toad.

The unit was put together at the workbench with an installation harness attached. I found it best to tape the two relays together with electrical tape and then the small circuit board was tie wrapped to the relays. I soldered the surpression diodes to the coil leads of the relays leaving enough room to still have a spade lug connection.  All other connections to the relays are done using female spade connectors. The two additional diodes were connected to the appropriate spade lugs and insulated with heat shrink tubing. It takes about 4 hours to put it all together with appropriate length wires used as a harness for toad installation. The unit is very compact and I was able to install it in base of the Mini tail light well. From here all the connections required were made withing this tail light area. Your location may vary, but given all the required wiring was routed through this area of the Mini, when I set the car up for towing, it all worked out quite well.

One other handy tip is they make a piggy back female spade connector that has an extra male lead attached. This allowed me to add an additional wiring connection points to the spade lugs of the Roadmaster diode packs without altering any of the existing wiring that was already installed on the tail light diodes. This was helpful in tight places.

This could make for a good rainy day project if you are so inclined....

Later Ed