philcarrell Posted April 1, 2023 Share Posted April 1, 2023 On my 08 Executive my brake lights won't come on the coach and the toad. I have checked a 5 amp fuse in the FRB and a 15 amp fuse in the RRB. I have looked for a brake light switch on the brake pedal and cannot locate one. Does anyone know where the brake light switch is or any other clues as to what else could be wrong. Link to comment Share on other sites More sharing options...
jacwjames Posted April 1, 2023 Share Posted April 1, 2023 Check the firewall, I know on earlier models there are 2 switches on the firewall. Link to comment Share on other sites More sharing options...
philcarrell Posted April 1, 2023 Author Share Posted April 1, 2023 Will look there Link to comment Share on other sites More sharing options...
Capt Mike Posted April 1, 2023 Share Posted April 1, 2023 I had the same problem on my 08 Knight, I believe one of the relays in the FRB was the culprit. Very stupidly I pulled several and tested not really knowing which one was faulty. The “switches” on the firewall we’re fine. Link to comment Share on other sites More sharing options...
philcarrell Posted April 1, 2023 Author Share Posted April 1, 2023 I replace the relay labeled brake light switch, didn't fix it. Will check again for another one. Link to comment Share on other sites More sharing options...
Steve P Posted April 1, 2023 Share Posted April 1, 2023 My '08 Knight has 2 relays having to do with brake lights. The first was in the front left bay. The other one was in the right rear bay. Check your wiring diagram or the label on the inside of the dust cover. Link to comment Share on other sites More sharing options...
philcarrell Posted April 1, 2023 Author Share Posted April 1, 2023 Found one in rear will look in front for another one. Link to comment Share on other sites More sharing options...
jacwjames Posted April 1, 2023 Share Posted April 1, 2023 X2 on checking a wiring diagram. Your coach is several levels above mine and newer so who knows what could be the problem. I don't leave home without my wiring diagram😁 Link to comment Share on other sites More sharing options...
Cubflyer Posted April 1, 2023 Share Posted April 1, 2023 I have the same problem currently, but my MH is not close by so I have not been able to repair it. That said, I do believe the brake light switches are in the area in front of the brake pedal, forward of the firewall, accessed by the generator. I have two switches there on an air line manifold. I believe they are the problem, and would like to have replacements in hand before I contort myself up in there to replace them. Still looking for a source for replacements... Maybe your lights are not working for the same reason. Ken Link to comment Share on other sites More sharing options...
Scotty Hutto Posted April 1, 2023 Share Posted April 1, 2023 One other item to check is that most Monacos have a wiring harness connector in the rear of the coach; over time that can lose connection. On my coach it was inside/“behind” the roadside taillight assembly. Note: NOT the connector for the individual tail light; this is a slightly larger connector that goes to both taillights, the center brake light, and the toad/trailer connector Find it, spray it with contact cleaner or WD40, plug and unplug a few times to “clean” the connector, and see if that helps. I know of a few other folks who have had this pop up, plus, it’s easy to check compare to some of the other troubleshooting. 🤣 2 Link to comment Share on other sites More sharing options...
Capt Mike Posted April 1, 2023 Share Posted April 1, 2023 I too originally thought the Nason switches up front were the root of the problem. I located the manufacturer and learned of a 45 day wait on manufacturing for two. Went looking elsewhere, my bet is on the relay front or rear. Link to comment Share on other sites More sharing options...
philcarrell Posted April 1, 2023 Author Share Posted April 1, 2023 Ok after checking everything I finally found a 15 AMP fuse in FRB that was blown. Now brake lights work. That was easy to overlook. However I am always wanting to know why the fuse blew. So some more research. Thanks for all of the tips, glad to be a member of this group help is always a few keystrokes away. 1 Link to comment Share on other sites More sharing options...
Steve P Posted April 1, 2023 Share Posted April 1, 2023 @philcarrell You might start with this angle in determining why your tail light fuse blew -- One thing worth checking if you tow, is the condition of your trailer plug. Mine was cracked and twisted slightly and I found that it seemed to be the cause of overload on the taillight circuit. That seemed to affect my relays for some reason, but did not blow a fuse. It's still a mystery to me, but after securing the plug and cleaning the contacts, and tie wrapping the trailer plug in place firmly, and after replacing the relay, the problem is eliminated. At least for now. The plug is on my list of things to replace. With all the water and dirt that it gets blasted with, it's a surprise it works at all... The other thing would be the connector contacts that @Scotty Hutto mentioned. I've added that to my insanely long to-do list. 😉 Link to comment Share on other sites More sharing options...
DennisZ Posted April 2, 2023 Share Posted April 2, 2023 I had this issue with my 08 Endeavor last year, it turned out to be bad brake light switches, both the primary and secondary switches were bad. The switches were the Nason switches, but they were $$$ and a long wait time, I was able to get “generic” switches used by the trucking industry at NAPA. I did have to remove the treadle valve from the firewall to replace the switches, but with 2 people it was only about an hour or less task. 1 Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted April 2, 2023 Share Posted April 2, 2023 (edited) Hi Phil, we haven't heard from you in a long long time. Hope you have both been well and still RVing. 7 hours ago, DennisZ said: . The switches were the Nason switches, but they were $$$ and a long wait time, I was able to get “generic” switches used by the trucking industry at NAPA. I like the idea of generic switches, readily available. Those look like the switches on my air tanks. 7 hours ago, DennisZ said: it turned out to be bad brake light switches, both the primary and secondary switches were bad I have read that 2 switches are as a backup, but what good is a backup if we don't know when the 1st sw goes bad? Or did a dash warning light come on? Edited April 2, 2023 by Ray Davis Link to comment Share on other sites More sharing options...
DennisZ Posted April 2, 2023 Share Posted April 2, 2023 One is the primary system the other is the secondary system. My first indication something was wrong was my cruise control wouldn’t disengage when I pressed the brakes. Link to comment Share on other sites More sharing options...
Steve P Posted April 2, 2023 Share Posted April 2, 2023 @DennisZ "One is the primary system the other is the secondary system. My first indication something was wrong was my cruise control wouldn’t disengage when I pressed the brakes." i have that exact problem intermittently... so does that mean one of my brake switches on the firewall in the generator compartment is going bad? Are these air or electric? I don't even know what they look like... Link to comment Share on other sites More sharing options...
DennisZ Posted April 3, 2023 Share Posted April 3, 2023 23 minutes ago, Steve P said: @DennisZ "One is the primary system the other is the secondary system. My first indication something was wrong was my cruise control wouldn’t disengage when I pressed the brakes." i have that exact problem intermittently... so does that mean one of my brake switches on the firewall in the generator compartment is going bad? Are these air or electric? I don't even know what they look like... They are air actuated switches, they are mounted to the brake treadle valve on the firewall, the valve needs to be removed in order to change the switches, I didn’t have to break any of the air lines, I had plenty of room to get the valve to where I could work on it. If you are having the same issue as I did, you have 2 bad switches, if one is still working you won’t see any issues. The switches are a pressure range of 4 +/- 1 PSI to activate, they are a N.O. Circuit. The original switch loosk like this one, it has 3 wires, but only 2 are used. 1 Link to comment Share on other sites More sharing options...
Steve P Posted April 3, 2023 Share Posted April 3, 2023 Thanks DennisZ... that gives me a good start. If I can't figure the rest out by reading other threads, I will start a new thread for the braking & cruise control problem. Apologies to Phil for the rabbit trail off his tail light thread. Link to comment Share on other sites More sharing options...
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