Brake lights on when retarder is on

[Pigman1]

On our 2013 Tiffin Allegro Bus with a Tiffin Powerglide Chassis the brake lights DO NOT come on with the activation of the engine compression brake. On a former Allegro Bus with a Freightliner Chassis, the brake lights DID come on with the activation of the compression brake.

Right after we took delivery of the new Bus, we had a trip to the southwest, and this summer we took another trip with it to Alaska and back. With a total of over 23,000 miles, many of which were steep mountain driving, I found that traffic coming up behind me tended to get a lot closer and seemed about to run over me when driving the new Bus vs the old Bus. This was the 6th trip to Alaska and the 12th to the southwest, so I had some experience to compare one to another.

I did a bit of research on Federal Motor Vehicle Safety Standards regarding this difference. FMVSS's give manufacturers the option to have the brake lights illuminate or not when the engine brake/retarder is activated.

Since my preference was to have the lights come on with the engine brake, I asked Bob Tiffin if I could get the Cummins ECM reprogrammed to allow this to happen. He agreed, and the new Bus ECM was reprogrammed. All was fine until I tested it. The brake and brake lights worked just fine, however, the Check Engine light came on and would not extinguish. After a week or so of research we found out the following.

When the engine brake comes on in a Freightliner chassis, there is a light that illuminates on the coach dash showing that it is on. The Powerglide chassis instrument panel does not have any light to show this. If the ECM is programmed to turn on the brake lights with the engine brake, it also sends a signal to the instrument panel cluster to turn on the dash light. When it does not see a signal from the dash that this light is ON, it illuminates the Check Engine light and keep it on until reset by a technician with a laptop and a CUmmins program.

My preference is to have the coach brake lights on with the engine brake, however this is not possible with my present chassis. I'm stuck without a choice due to the way the coach was designed and built, but it is not contrary to any regulations, and I'll just have to live with it. For those with a Cummins engine, the change can be made as long the chassis setup and hardware can accommodate it.

[hes4all]

Originally Posted by palehorse89

Like Cooperhawk stated about "big trucks", thier brake lights do not come on when using thier engine brake. This is a RV Chassis mfg. addition and it is not a law that they come on when using engine braking. On my Spartan MM Chassis in the rear compartment in the fuse block there was a diode for the brake light operation, Spartan tech said if I did not wish to have them come on when using the engine braking.....pull it .....no more brake light. The problem was like stated when pulling my trailer when the light came on my trailer brakes also came on,(no more braking after pulling the diode) and along with the fact that I did not wish to have my brake lights on drifting down off a 7 mile long hill when I was "not slowing" but just maintaining the posted speed. Like always.... just my personal preference on this subject.

Like he said, my Jake is for just holding my speed. I am also going to look for the diode in the rear of the coach. That would have been easier than what I did. Even though it took about 20 minutes to do it.

[hes4all]

Originally Posted by Dr4Film

Sorry, again I have to respectfully disagree.

I've been pulling a 30 foot trailer since 2009. I did all of the wiring myself and my trailer electric brakes ONLY come on when I step on the air service brakes.

My rear brakes lights both on the coach and the trailer come on when descending a grade while using the PacBrake Exhaust Brake.

That's they way it should work and if it doesn't then the person who did your wiring had done it incorrectly.

Dr4Film ----- Richard

Richard, maybe with you wiring your coach yourself you did it the "correct" way. I have had three DP's and all sent the signal to activate the brakes when I used the Jake or exhaust brake even on my 2001 Cat.

And I have seen trailers being pulled by rv's in Colorado that the brakes were smoking. I even talked to one guy who was shocked when he pulled over at a rest area.

But to each his own. Thats what I love about this country and this forum. Many opinions that are good in many ways.

[hes4all]

Originally Posted by palehorse89

On my Spartan MM Chassis in the rear compartment in the fuse block there was a diode for the brake light operation, Spartan tech said if I did not wish to have them come on when using the engine braking.....pull it .....no more brake light. always.... just my personal preference on this subject.

Where was the fuse block in your coach. I have a 06 MA so maybe they are different? Thanks

[Libero]

On my both my Monaco DPs, only the brake lights came on when the exhaust brake was on. This was not electrically connected in any way to the toad/trailer brakes but of course the toad brake lights would come on when the RV brake lights came on.

Do not understand the electrical connection between the RV brake lights and the toad/trailer brake controls. I used air from the service brakes to activate my toad brakes and I had an electric brake controller for a trailer and now I use a ready brake for a toad and it comes on when it detects retardation in the RV. Have never seen a brake control circuit and a brake light circuit electrically connected. Perhaps they exist????

[Dr4Film]

Originally Posted by Pigman1

On our 2013 Tiffin Allegro Bus with a Tiffin Powerglide Chassis the brake lights DO NOT come on with the activation of the engine compression brake. On a former Allegro Bus with a Freightliner Chassis, the brake lights DID come on with the activation of the compression brake.compare one to another.

My preference is to have the coach brake lights on with the engine brake, however this is not possible with my present chassis. I'm stuck without a choice due to the way the coach was designed and built, but it is not contrary to any regulations, and I'll just have to live with it.

Personally, I would think that you would NOT have to live with it that way. I understand that you can't reprogram the ECM BUT you could do some creative wiring to make the rear brake lights come on when you activate the Jake Brake.

I would use a relay wired into the foot pedal switch such that when you press on the foot switch to activate the Jake Compression Engine Brake, it would then activate just your rear Brake Lights.

I bet I could do it if I knew where your wiring was located, etc.

Essentially, you would use one 20 amp automotive 5 pole relay similar to this one.

20 Pcs 40 Amp Bosch Style Automotive Relays Sockets Car Wiring SPDT Relay | eBay

Look at the wiring schematic in the eBay ad.

If your Jake Brake foot switch has a 12 VDC positive signal running through it then all you would need is a parallel wire from the Jake Brake Foot Switch to the trigger terminal Pin #86. That has to be a 12 VDC Positive power signal. If it isn't then another wiring plan would need to be put together.

Next is a ground wire that would go to Pin #85

Pin #30 would be the wire that goes to your brake light wire. (Hopefully your brake light wire is a 12 VDC Positive wire) (I know that Monaco uses 12 VDC negative to switch the brake lights as I had to do some creative wiring for my electric brake controller)

Pin #87 would be a wire that has 12 VDC Positive power on it.

Pins #86 & #85 activate a coil inside the relay. When there is 12 VDC power to pin #86 from your foot switch, then the coil closes which activates a switch inside the relay which are Pins #87 and #30. When the switch closes your brakes lights come on.

That's it.

What do you think?

Dr4Film ----- Richard

[ShapeShifter]

Originally Posted by Libero

Do not understand the connection between the RV brake lights and the toad brakes. I used air from the service brakes to activate my toad brakes, and now I use a ready brake and it comes on when it detects retardation in the RV. Not brake light circuit related. Confused?

It all depends on the braking system. Some of them use an electrical signal from the coach to activate the toad brakes. I have the US Gear Unified Tow Brake, and it works just like many electric trailer brakes.

Many electric trailer brakes use an electrical trigger signal from the tow vehicle. This is commonly wired to the brake switch, and is most easily done by tapping into a brake light wire. When the tow vehicle brakes are applied, the trigger signal is activated, and the trailer brakes are applied - sometimes in proportion to an acceleration sensor, sometimes using a simple timing, sometimes using other methods.

The US Gear Unified Tow Brake, and I'm sure others, work the same way: Just like an electric brake controller, there is a control box mounted by the driver, and it has the same type of gain and manual application controls found on many electric brake controllers. When it gets the brake switch signal, it activates the toad brakes in proportion to the deceleration it senses.

If a toad or trailer brake that uses a brake switch signal is wired up to a circuit that also comes on with the exhaust/engine brake, then the trailer/toad brakes will activate going down a long hill, resulting in the overheated/smoking brakes described earlier in this thread.

Like many Monaco built coaches, mine was pre-wired for the Unified Tow Brake, and there is a dedicated trigger wire that is hot when the service brakes are applied, and not when the exhaust brake is applied. Interestingly, this same circuit feeds the lighting circuits in the 7-pin trailer plug by the hitch.

This means that the coach brake lights come on with either the service brakes or the exhaust brakes. But the toad/trailer brake lights only come on only with the service brakes. So, when I'm going down a hill with the exhaust brake on, the coach brake lights are on, but the toad brake lights are off. If I squeeze the service brakes to bleed off a little speed, the toad brake lights come on, but go out again as soon as I let off of the service brakes.

I found this out when a friend was following me. It was a surprise. But after talking with other RVers I find that this is not an unusual situation, and looking at the wiring diagrams it is operating according to the way it was designed.

[hes4all]

When i spoke with Cummin's I was told that the power back feed when the Jake brake was activated. That turn the light on in the dash and feed back to turn the brake lights on.

This also sent a signal to activate the trailer brakes. And yes, I would like to have my coach brake lights on when I an using the Jake with the trailer on.

As of this time with the diode, my coach brake lights only work with the foot brake.

I have two friends, one with a Travel Supreme and the other with a 04 DS and the coaches had the same deal as mine. We do a ton of mountain driving each summer and use the Jake just to hold our speed.

My buddy with the Dutch Star did burn his trailer brakes up three years ago before he put the one was diode in.

The diode still allows for the dash Jake light to come on but doesn't allow for the signal to go to the lights.

I will look at my coach and call Newmar to ask about the diode in the rear fuse box.

Good responses here.

[Libero]

Thanks Sharpshifter

But the brake light circuit voltage has no proportional relationship hence they are on or off. Most brakes are applied with a proportional representation either by air, hydraulyic, or mechnical force or a change in voltage (resulting in a change in current). I therefore do not understand how applying a steady voltage as is presented in the brake light circuit would allow for proportional braking on the towed vehicle.

There must be something else in play other than the brake light circuit.

[mel s]

Originally Posted by Bumps

I prefer my brake lights to come on when I am decelerating. The message I want people behind me to get is, "I'm slowing down." I'm just not bothered about random wonderments about my brake pads.

X2!
Because my brake lights did not originally come on with the PacBrake activated, I wired them so they do!...(better that people know I am slowing down than risk getting rear ended).

BTW, the activation of the brake lights of my coach has NO affect the brakes on my toad.

Mel
'96 Safari

[lanerd]

When going down long (several miles) 5 to 6 percent grades, my exhaust brake can keep my coach and toad at a pretty even and safe speed. Unfortunately, from this post and replies, it is also applying the toad brakes and that is NOT GOOD. My last coach (Safari Simba) did not apply the toad brakes or even turn on the mh's brake lights.

I need to research this a little more....wasn't aware that this could happen.
Ron

[ShapeShifter]

Originally Posted by Libero

Thanks Sharpshifter

But the brake light circuit voltage has no proportional relationship hence they are on or off. Most brakes are applied with a proportional representation either by air, hydraulyic, or mechnical force or a change in voltage (resulting in a change in current). I therefore do not understand how applying a steady voltage as is presented in the brake light circuit would allow for proportional braking on the towed vehicle.

There must be something else in play other than the brake light circuit.

Re-read what I wrote, I think you might have missed the mention of the controller. Or maybe I wasn't clear enough. (I just re-read what I wrote, I didn't directly mention the controller, just made an indirect mention when talking about my toad brake - sorry for the confusion.)

A typical electric brake controller is triggered by the on/off brake signal, and then uses an accelerometer or pendulum to monitor the tow vehicle's braking rate, and uses that plus a manual gain control to calculate the proportional signal to send to the trailer brakes. Simpler units just use a timer, and vary the trailer brake signal according to a fixed profile, regardless of the actual braking effort. The most sophisticated controllers tie into the tow vehicle air or hydraulic system to directly measure the braking effort, but these aren't used as often (unless installed by the factory) because the installation is more complicated. But the key to all of them is that they aren't triggered until the brake switch is active: you can do some serious downshifting to slow down without the trailer brakes coming on.

My toad brake has a controller in the MH cab, that has an accelerometer to measure the braking effort and proportionally apply the toad brakes. The principle is exactly like a momentum based electric brake controller, such as the popular Tekonsha Prodigy. Like the typical brake controller, it does nothing until it sees the brake switch active. Since my trigger line doesn't come on with the exhaust brake, I can be slowing down quite aggressively with the exhaust brake, or going down a long hill with the exhaust brake, and not be applying the toad brakes.

So I think my coach is wired the best way possible: coach brake lights come on with the exhaust brake, but toad brakes not triggered. Although I sometimes wish the toad brake lights would come on with the coach brake lights when using the exhaust brake: it must seem strange for people behind me to see the coach brake lights come on continuously during a long descent, but the toad lights only come on occasionally when I use the service brakes.

[Pigman1]

These new coaches are quite different from older ones. For example, the fact that the engine ECM "knows" when a warning light on the dash should be coming on, and when it doesn't see that happen, it "knows" it has to turn on the check engine light. All this is done through a single wire and uses digital multiplexed signals transmitted back and forth over these wires from the engine ECM. Another example of how bad this is is as follows. I found that I had no headlight warning that told me that my lights were on after I turned off my key. An internet search found a simple circuit that I could pull off the light switch and ignition switch and run these wires to a piezo buzzer. No sweat, right? WRONG! There's no 12v power at the ignition switch. And, there's no 12v power at the light switch. Both only run control circuits to the lighting computer. I got around it by running wires to a switched 12v wire I found under the dash, and another run to the left front parking light, but this shows how complex simple wiring can get with all these digital controllers on newer rigs.

I probably could probe around on the engine and on the engine wiring harness to find a 12v activating circuit, but back feed problems on these computerized circuits can cause undesired things to happen in the engine ECM, and those things are somewhat expensive. Don't think I'll go there just yet.

[ImagineIF]

I live on the east coast and dudn't mind the brake lights coming on when the Jake was active. Then I spent time out west and decided the brake lights shouldn't be on for the entire run down a long grade. Prevost conversions have a rlay that is activated by the Jake or transmission retarder (depending on what you have). That relay has now been removed.

FWIW, it's okay to have your TOAD's brake lights activated by the supplementary braking system. However, they are required to come on when thr coach is braking. This probably not in sync with when the TOAD's brakes are being applied.