Hey guys, I have a few questions ... The truck was bought last year... Not being used yet. I bought a 12 Tag to haul my Backhoe , So I'm going over the lights... Blinkers were backwards , but easy to fix. Finally the wife is here to Jump in the cab and give me help Hmmm, After getting NO brake lights on the Truck... First place I tested was the Fuses on the Passenger side Dash panel... The Brake lamp Was "Hot" both sides of the circuit breaker... Odd thing... The line is Hot with the key "OFF" but key on...Nothing... I tried the brakes with key off too... No brake lights... I tried testing the senders under the hood... Two pressure senders........... Two pole , and three pole... Nothing would go hot ( Key on or off hitting brakes ) I tested the rear Trailer socket... No Joy , Key on or off . First Question... Should I move wires at the ignition switch to make the Stop lamp HOT during "Key on"... From there... I need hot to the sender right , so it can pass it to the lights? Any Idea why TWO senders ? Is it the Trailer Hand Brake and the regular Foot brake ? . Thanks for any reply... JAM
Here's the two and three pole senders...
I put a hot wire to one of the TWO pole pressure switches... Brake Lights Work... and pressure switch. I have Hot to both sides of the Stop Lamp Circuit Breaker... So tomorrow I'll run a jumper by pass wire...just temp... I had to tape some wires a Mouse chewed over Winter...
Well... I tracked it down... There's a Terminal Bank under the hood , on the firewall. There was a connector that eroded and broke off... THAT was the MAIN problem. A real 8itch was connections... They needed to be wiggled. one at the pressure switch (I'm just gonna replace it) and at the Trailer plug... I gotta clean it more and maybe anti-seize ... This stuff is impossible to do by yourself , unless you have a BIG MIRROR Now I've gotta get the trailer running lights working. Gotta Fly...
Clean the plug up good with brake cleaner, plug brush if you have one. Then squirt di-electric grease in the plug holes to keep corrosion down. You can also spread the male pins in the truck end ever so slightly with a small screwdriver. Not too much they'll break. Clean the trailer end with brake cleaner and a brush as well. Get all the funk out of it and greased up nice. That will help with plug issues. If they're bad just replace them and keep them greased. Heat shrink terminals anywhere you replace one. Don't be afraid to dob some grease on the terminals as well to keep corrosion down. Junkyard
Thanks JY, I just got done putting Anti-seize on them just to do more testing ( Running lights) First thing I did when I bought the truck was GREASE my battery connections... I can clean the Plugs later with the Starting Fluid and grease them... I use Starting fluid instead of brake clean... It's cheaper... and it can be used as Starting Fluid too. Brake clean is dangerous to weld on...Bad Fumes. The Truck should be in good hands... I'll be doing stuff like you mentioned as preventive maintenance.. Nothing worse than RE fixing. . Also, I don't plan on Winter work with the Truck... But still a good Idea to seal things from weather. . Gotta Fly... .
Looks like I still have a problem... I think the right rear light on the truck is wired backwards ? I need to get in there with a 12V tester tomorrow... But things are VERY close now. Gotta Fly...
The reason for two brake switches is one each for the primary and secondary systems.
Two pole and three pole pressure switches... Is the three pole the Trailer Hand Brake ? Is that the secondary ? I guess I could pull the hand brake and test the pressure switch with the 12V probe
Yes you can test it like that. They were probably the same and one was changed out, either will work. I thank your three pole still has only two wires to it but can be wired for N/C or N/O.
There should be a third switch for the low air alarm, they can look the same. Your straight truck has a hand-trolley valve for the trailer? I will try to remember to look at the one here but yours is newer and maybe different.
Yeah... The three pole switch might throw the alarm ? I was thinking about probing it...12V I'd be able to hear when the buzzer quit... and see the connection.. My Truck used to be a three axle... Still has the diff Lock-out too...well... the switch. It's my BIG little truck. L-10 Cummings (315 hp) w/Spicer 10 speed
Greetings. I am experiencing a similar problem. Saw your reply from this old thread...hope I can still ask some questions. I have juice to the 3 Wire switch, but not the 2 wire? WHich is primary? Will either one activate the brake lights? Should it work with only the one? Thanks Ron Z
12 volt systems suck. They are exposed to corrosive fluids, and are exponentially more sensitive to a bad connection than 120 volt household lighting. There are three causes of failure in automotive electrical systems: Destruction, chafing, (insulation failure), and (most common) connection deterioration. Wiring harnesses make it very difficult to follow a wire. Most frequently old truck wire failures are due to bad connections.
Again I have one in the shop if I remember to look. We are soooooo busy. Both will activate the brake lights. It likely ( should have ) two low air pressure switches also. There are two and three terminal switches that will probably work in either application. Many things may have been changed over the years so do not go by the number of terminals. They can look the same. Pictures? The switch with power on one side: Does it have power to both sides with or without pressure on the gauges? With air and the service brake applied? What happens if you jump it? Similar problem? What is the problem with yours?
Thank you, Ten... I got power to both switches: corrosion. IT appears that the switches are working. I also jumped across them, and no lights. So, it appears that it is in the wring beyond the switches... So now it's a matter of following wires. Thanks!! Ron
If I remember correctly and I am not sure. But some of those had a solenoid tucked up behind the air cleaner that powered up several circuits. It was a typical solenoid you would find on the fender of their pickups. Might be something to check for.
Thank you!! WIll do.
Next suspect is the turn signal switch. Power goes from the brake light switch to the turn signal switch. It is the the T S S 's job to break it out. It uses the same wires to send brake or turn signal power to the tractor rear lights and the trailer wires are separate. Some of those Signal Stat turn signal switches had wires in different places on the connector plug. Have to move them around to match yours. I am not familure with that deal Theweldor mentioned but 9000,s were made for a lot of years. They are not all the same. Good Luck: Keep us updated.
It has been years since I have worked on them. They did have some different designs but once you figured them out they were pretty simple. Totally forgot about the turn signal switches definitely something to check.
Ten: The turn signals and emergency flashers both work fine. Could it still be the TSS?? I put a new one in about a year ago. Could be a wiring issue....
What exactly is going on with your truck? Is it a semi tractor trailer or a straight truck? If a straight truck pulling a trailer that can also be different. We need some more info. Testing and repairing the problem is most always better than throwing parts at it. It is past my curfew and I have to hit the ground running in seven hours. Maybe catch you tomorrow night.
This is a tractor, pulling a trailer with electric brakes. Flatbed with hay. It's a single axle with a 10 liter Cummins.
Nice setup. Most folks just wire a plug on the rear of tractor for the trailers like that. You should have a wire to the turn signal switch that is hot when the brake pedal is pressed. Key on with air up of course. The signal switch interrupts the brake circuit for which ever signal is turned on. The brake and rear turn lamps share the same wires from the switch to tail lights. If you are wired to the trailer plug on back of cab they have a brake light wire seperate from the turn signals. Wired different than most trailers with electric brakes.
Greetings all. THanks so much for the help. The problem was in the wiring from the turn signal switch, which I had installed about 6 months ago. I had two wires switched...funny that I had not noticed it before, but I dont drive it that much... But, summer's coming, so they say. Anyway all the help is much appreciated. Take care...and remember: The Early Bird might get the worm, but the second mouse gets the cheese.