Third Break Light not working

[bnd10706]

I have a new to me 2008 Winnebago Sightseer 35j.

I was following behind my wife when we were driving it home from an event, and I noticed that the 3rd break light was not working.

I figured it was just old and I ordered a new one. upon hooking up the new one and testing it, it did not work...

I cant see much in the way of wiring, there are 2 wires that come out a white and a yellow and i assume they come from the same wiring for the other break lights.

I am not sure there is any easy way to check on these wirings... but im looking for any advice.

[Ray,IN]

FWIW, over 80% of all 12V issues are the result of a poor/missing ground. That is easily checked with a continuity tester. Same for the existing wires, test for continuity, both pos and neg.

[bnd10706]

So I am still struggling with this...

I have checked all the fuses, and I have checked all the wires to the best of my ability.

I have hooked up a voltmeter and when the brake is applied I am getting no voltage readings.

I dont know what to do here.

[l1v3fr33ord1]

bnd10706-

The wiring diagrams for a 2008 Sightseer 35J are at this link. The Auto Lamps Wiring Diagram shows how the third brake light is wired. Make sure you use the sheets that are correct for your chassis manufacturer- either Ford or Workhorse ("WH").

[bnd10706]

Originally Posted by l1v3fr33ord1

bnd10706-

The wiring diagrams for a 2008 Sightseer 35J are at this link. The Auto Lamps Wiring Diagram shows how the third brake light is wired. Make sure you use the sheets that are correct for your chassis manufacturer- either Ford or Workhorse ("WH").

Thank you! that was extremely helpful. Im not super knowledgeable in this, but I think i have a starting off point here.

I have the ford chassis so it make a bit more sense.

[Morich]

Just some thoughts after looking it over a bit.
This may be one that I would have to consider HOW BAD I wanted it fixed???
I'm looking at it as being a connection that may be up under the rear cap and require removing that to get to the connection!!! OUCH?

This drawing, sheets 3 and 5 show the connections and we get wire ID from this list:
https://www.winnebago.com/Files/File...0167477022.pdf

https://www.winnebago.com/Files/File...ical_guide.pdf

So it seems to go from the light up to a plug under the rear cap to meet the main feed and then to a plug that they do not give location?? If one could locate that main connection and find battery there, I'm guessing the next most likely spot to go open would be under the cap!

First pic is the light and showing plug that mates to second picture before going on to main plug. My thoughts might run that if the brake lights on each side are working but not the center, the wiring front to back is okay but open somewhere near the rear and that is where I get the thought it is under the rear cap??




This drawing, sheet 2 shows this at top right corner:

https://www.winnebago.com/Files/File...ire_162635.pdf

Click these snips for better view.


See if that meets what you see?

[bnd10706]

Wow Richard thank you!

Looking at the wires themself, i was concerned that it went up.

Im just mildly concerned with the brake lights. obviously the more visibility the better.

We are going to be flat towing in the summer, so having something over the tow vehicle would be nice.

I wonder how hard it would be for me to run 2 wires down to one of the rear brake lights and just tap off that..

-Brandon

[bnd10706]

I guess my question here... what is the best way to TEST these wires? my voltmeter was not working...

I assume taking the rear cap off would also require to remove a bunch of sealant?

[Morich]

Hard to get a wire up from below and inside the back wall as it is likely to be a "sandwich"of outer over foam wall and then inner surface. Punching a tool of any kind through the foam for the distance might be a real trick that I would not bet too much on doing?? But it might also only need to be one wire if you can determine the ground wire side (white that they call TP? is giving good ground, then all you would need is a single wire from one of the brake lights or even the trailer hitch connection for giving the other side that goes hot when we step on the brake , going to the center light.
On the other hand, if the old rig is not a pretty as it once was and a small wire run on the surface under some tape, etc to hold and hide it, maybe a short cut is needed?

What about running a wire from the center light up to the top, tuck it under the bottom of the cap and go left or right and down the corner molding to one of the brake lights there?

I've never pulled the caps off the rear and never felt it would be easy as there is likely to be tons of sealing from all the years and as fiberglass gets older, does it get more brittle?

Any chance you would like a big decal in the space between the light and the rear cap that might just happen to hide a wire?

Throwing in some ideas without much to back them!! Like RV, some of us older folks have a few faults we try to hide!

[bnd10706]

Originally Posted by Morich

Hard to get a wire up from below and inside the back wall as it is likely to be a "sandwich"of outer over foam wall and then inner surface. Punching a tool of any kind through the foam for the distance might be a real trick that I would not bet too much on doing?? But it might also only need to be one wire if you can determine the ground wire side (white that they call TP? is giving good ground, then all you would need is a single wire from one of the brake lights or even the trailer hitch connection for giving the other side that goes hot when we step on the brake , going to the center light.
On the other hand, if the old rig is not a pretty as it once was and a small wire run on the surface under some tape, etc to hold and hide it, maybe a short cut is needed?

What about running a wire from the center light up to the top, tuck it under the bottom of the cap and go left or right and down the corner molding to one of the brake lights there?

I've never pulled the caps off the rear and never felt it would be easy as there is likely to be tons of sealing from all the years and as fiberglass gets older, does it get more brittle?

Any chance you would like a big decal in the space between the light and the rear cap that might just happen to hide a wire?

Throwing in some ideas without much to back them!! Like RV, some of us older folks have a few faults we try to hide!

All Great ideas!

I might look at just plugging the hole...

THank you for all your research!

[l1v3fr33ord1]

bnd10706-

Here are some thoughts:

1) If you've had the brake light out, do the two wires go up or down, as near as you can tell?

2) Can you access the two-pin connector?

A note of caution here: One slip and the wires can disappear inside the end cap. When I did third brake light work I made sure to extract the connector from the hole (carefully), put a clamp (large enough not to go through the hole) on the wire upstream of the connector, and tape the wires to the cap.

3) You can usually find those two Ford connectors on the driver's side of the frame at the rear, somewhere out in the open. The wiring comes up from below the third brake light, not above it. That's what I would look for and test next.

4) Or, you could look one other place. According to the wiring diagrams (link here, sheet 1, zone C-1), Winnebago shipped the coach with wires to add a trailer electric brake controller. The brake wire in that bundle is spliced at the same point as the brake wire for the third brake light. If you get 12V at the trailer electric brake controller input wire, but not the third brake light, then you'll know the signal get lost between the two points (probably at the Ford connector mentioned in thought 3), above). It may take some digging, but the trailer electric brake controller prep wires are under the dash, on the left side of the steering column. See same drawing, sheet 1, zone B-7. Some folks report that it's easier to get at the wiring in that area if you unbolt the Ford interior fuse panel from above the Winnebago circuit breaker panel that's near the driver's left shin.

5) From pictures and descriptions, removing the rear cap is a big job, and to be avoided.

6) I encourage you to find and fix the problem, as built. Should you determine you must tie into the coach's rear stop/turn lights to feed the third brake light, you'll need to install a converter to filter out the "turn" part of the signal. A Curt 56196 converter (link here) should do the job.

7) It may not apply where you live, but in my home state a coach will fail annual inspection if the third brake light does not work. That's why I ended up replacing my coach's third brake light a few years ago.

[bnd10706]

Originally Posted by l1v3fr33ord1

bnd10706-

Here are some thoughts:

1) If you've had the brake light out, do the two wires go up or down, as near as you can tell?

2) Can you access the two-pin connector?

A note of caution here: One slip and the wires can disappear inside the end cap. When I did third brake light work I made sure to extract the connector from the hole (carefully), put a clamp (large enough not to go through the hole) on the wire upstream of the connector, and tape the wires to the cap.

3) You can usually find those two Ford connectors on the driver's side of the frame at the rear, somewhere out in the open. The wiring comes up from below the third brake light, not above it. That's what I would look for and test next.

4) Or, you could look one other place. According to the wiring diagrams (link here, sheet 1, zone C-1), Winnebago shipped the coach with wires to add a trailer electric brake controller. The brake wire in that bundle is spliced at the same point as the brake wire for the third brake light. If you get 12V at the trailer electric brake controller input wire, but not the third brake light, then you'll know the signal get lost between the two points (probably at the Ford connector mentioned in thought 3), above). It may take some digging, but the trailer electric brake controller prep wires are under the dash, on the left side of the steering column. See same drawing, sheet 1, zone B-7. Some folks report that it's easier to get at the wiring in that area if you unbolt the Ford interior fuse panel from above the Winnebago circuit breaker panel that's near the driver's left shin.

5) From pictures and descriptions, removing the rear cap is a big job, and to be avoided.

6) I encourage you to find and fix the problem, as built. Should you determine you must tie into the coach's rear stop/turn lights to feed the third brake light, you'll need to install a converter to filter out the "turn" part of the signal. A Curt 56196 converter (link here) should do the job.

7) It may not apply where you live, but in my home state a coach will fail annual inspection if the third brake light does not work. That's why I ended up replacing my coach's third brake light a few years ago.

1. The light is off, and the wires go up

2. No, I cannot see anything beyond the 2 wires.

3. I have looked around the rear of the rig. From what I can tell there is a bundle of wires go up on the driver side down low. These wire bundles are in those plastic sock things(whatever the technical term is). So I have no idea where they go.

4. This is a place i can look... its actually very difficult to get to that area, just getting to the fuse box was a pain because of my body trying to bend around the driver seat in an awkward way. But I can at least poke around there. The brake controller is getting power... I am not actually sure if it works yet, I have not hooked anything up to it to test.

5. IF and this is a big IF i do that, i will take it to someone. I have thought about adding a forever roof on. If i do that, ill just have him to this before he does that. This guy specializes in RV roofs... The benefit of living in Florida is there are a ton of RV specialist.

6. I do know someone who builds the electrical system of police cars. He is the one that suggested taping into the rear brake light. Apparently there are 3 wires going into the light, one for the ground, one for turn signal and one for brake. I would jsut tap off the ground and brake, no need for a converter.

7. Here is Florida there is no inspection, so not an issue, and its not required. For me its more about the safety of driving. People are morons, and i really don't want someone hitting me because they are dumb, then sue and say its because I did not have that 3rd brake light.

[Morich]

At the trailer connection is one place that access to the wires is easy as the brake and turn are different wires as well as at the stop/turn lights, so which is easier may be best. Just several alternates on where..

[Morich]

Just as another alternate to consider, there is a product called flat wire!
I have seen it in small guage that would carry the low current for one center light and it was just less than half inch wide and very thin with adhesive backing.

Not finding the exact opne I had seen but something like this with adhesive and perhaps a wire molding to cover it all would look somewhat "normal" if running directly down the centerline in back?

https://www.amazon.com/Monoprice-Pla...0510175&sr=8-5

But another "amazing" thought? Wonder if there is a chance that the 2 pin connector might be found under the far left clearance light at top? Maybe they left is there for access?

[l1v3fr33ord1]

Originally Posted by bnd10706

2. No, I cannot see anything beyond the 2 wires.

3. I have looked around the rear of the rig. From what I can tell there is a bundle of wires go up on the driver side down low. These wire bundles are in those plastic sock things(whatever the technical term is). So I have no idea where they go.

6. I do know someone who builds the electrical system of police cars. He is the one that suggested taping into the rear brake light. Apparently there are 3 wires going into the light, one for the ground, one for turn signal and one for brake. I would just tap off the ground and brake, no need for a converter.

I'd be inclined to gently pull on the wires, looking for a connector. Or, better yet, borrow a cheap "borescope" camera and have a look around the inside of the cap at the brake light hole.

The Ford connectors are likely inside the bundle of wires on the driver's side "down low." It shouldn't be too hard to spot them. I'd follow forward from the trailer hitch connector.

Per the wiring diagram, the three wires to the taillights are:

1) Ground
2) Stop/turn
3) Parking

You may get to confirm this for yourself... hopefully fix it a different way.

[Morich]

Originally Posted by l1v3fr33ord1

I'd be inclined to gently pull on the wires, looking for a connector. Or, better yet, borrow a cheap "borescope" camera and have a look around the inside of the cap at the brake light hole.

The Ford connectors are likely inside the bundle of wires on the driver's side "down low." It shouldn't be too hard to spot them. I'd follow forward from the trailer hitch connector.

Per the wiring diagram, the three wires to the taillights are:

1) Ground
2) Stop/turn
3) Parking

You may get to confirm this for yourself... hopefully fix it a different way.

Fully agree with this on where and how we might find the wires. They are almost always under covers of some sort that make it hard to trace without cutting it all along with lots of mud!
Bundle of wires from the front to a plug where they split, some go left and others right to the taillights and split to go to the trailer connection. Another small bundle will connect to go up to the third brake light. This shows as going up the corner channel on the driver's side.

If the covers were off, it is likely to be easy to see what goes where but that stuff is hard to get off and back on!!

[bnd10706]

Originally Posted by Morich

But another "amazing" thought? Wonder if there is a chance that the 2 pin connector might be found under the far left clearance light at top? Maybe they left is there for access?

It is there!!

I guess the question is, now that I see it.... how do i know how to fix it? Is it the connector thats bad... the wire?

[Morich]

Part of that comes down to having a meter or inventing a way to test with other stuff.
I love the meter for easy clear answers!
But several things may help sort things.
Near the ends of the wires, there may be labels which help to tell us what each wire does.
That wire ID will show up as 1,2, or three letters that we can "decode" from this list:
https://www.winnebago.com/Files/File...ical_guide.pdf

On one drawing above, the two wires are ID'd as "X" being a yellow wire and "TP" as the white. So from the list TP shows as ground! Never trust things like that too far is you find different, though!
Likely to have two wires with one for ground and one for power when the brake is pushed, so it can help to know if you are missing battery power or ground, using the ID.
But with only two wires, it's not too much time to just test both for ground and battery!
Not like having a whole big bundle.

With a meter, holding one meter probe on something metal like any part of the frame will usually get a ground there, so putting the meter on DC voltage that is high enough to measure 12 volt, touching the other probe to each of the wires while somebody presses the brake, should show some reading around 12Volts, if that wire is good and also the correct one for the battery. If you don't find battery on one or the other, that is the problem, most likely, but while there, test to make sure the ground is also good!

Do that with the meter set to resistance, ohms or many meters have a funny looking upside down horseshoe symbol. One meter probe to a good ground and the other to the wires, should give you a reading.

In this case it is not important which meter lead to go where as we are not looking for the corect polarity of the battery, just that it is there. Same with resistance to the ground, no need to sweat which probe to go where!

If you have a plug, look at the points where the main wire makes contact with the wire going to the light. Any corrosion, rust, etc should be scraped to clear it. Sometimes just plugging / unplugging them a few times will clear the problem as they scrape each other together!

In fact, that may be the quicker way to clear the trouble before testing!

There are times when the wire breaks right where it goes into any plug and that may have to be cut off and reattached but not very often compared to just corrosion.
OR the worst case might be that the problem is way down right where the wires go into the normal brake light fixture. Down there you might have ten wires to sort which to look at for trouble.

I like the idea of it being where there are only two wires! but with the other brake lights working, you can be sure it is not something further forward or that harder stuff. It's right there close to the rear end---somewhere!