Freightliner Opt Switch Wiring Diagram

[Leysan Torri]

99Freightliner FLD semi tractor. Trailer has tail/marker lights with headlights on but not just parking lights. Left headlight works perfect on low beam, nothing on high. I'm sure the problem is the yellow wire because ALL the wires are yellow. Relays were labelled when it left the factory. Some still have tape on them. Not readable, but it is tape.

t-boss - 11/25/2013 20:51 On my 96 FLD the low beams will work all the time but you have to have the ignition switch on for the high beams to work. It took me awhile to figure that out the first time.If you sit and stare at the wiring diagram long enough you realize that is how it is supposed to be. Looking at the diagram the left low beam problem and the no trailer lights when parking lights are on issue is connected.

Does anyone have a wiring schematic for a series parrallel switch truck for the old setup with seperate switch and relay? The ones in the Wiki are all the newer style switch that I am going to but I have a few extra wires to identify. My original setup in the L model had the relay, switch, and 2 fuses next to the switch/relay between the seats if that helps. I already ID'd the battery cables (obvious), start switch lead, and power lead for the cab but have no idea what the rest is. I assume one is the charge from the generator/regulator. I am stuck upgrading the system due to the relay dying and not being rebuildable anymore. Please no banter about converting the starter to 12v. I want to keep the system 12/24v.

Thanks Dover but not exactly. That is a basic how to wire the switch but I am trying to figure what the truck has coming to the switch. It had a few more wires than that to contend with. So far I have 4 battery cables, start, ground, power feed through the amp meter for the cab acc and still have a couple of extras left over coming out of the harness. I am guessing that one is a wire from the generator but there is still 2 more that I haven't accounted for yet. This is after getting rid of the extras that go from the relay to the SP. It also appears that the ground is running through a fuse holder also and I still have another fuse holder next to that. Someone on another site posted up a schematic for a later mack but still isn't right to what I have. Its close but It may be what I have to work with it.

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I have a 99 Newmar, Dutch Star, pusher. Went for a state inspection found I have two brake lights out. One in the center up high is working. I have checked everything at my level. I am hearing there are diodes in the brake light circuit. Found a Freightliner bulletin and sure enough there is a brake light harness kit. Part number 06-28598-00 cost $182.00 plus shipping.

I was wonder instead of spend that much money on a new and improved kit, could I find out the value and part number of the existing diodes that I expect are blown and replace for a lot less money. Freightliner dealer said no, need to buy the kit. Of course they would, lol. I believe the diodes are located at the base of the steering column?

I don't know why you would have diodes in the brake circuit, and if you did it is unlikely they all have opened circuited. Fuses are used to prevent those problems. Typically, diodes are used on the tow vehicle. I think you're headed in the wrong direction.

Is your Freightliner chassis red stop and turn signals (3 way circuit) or does it have separate amber turn signals (4 way circuit). If you have red turn and stop lights I would suspect either a fuse or the turn signal multi-switch assembly. But it is very difficult to troubleshoot without wiring diagrams. Does Freightliner have chassis wiring diagrams for sale?

Also, you didn't elaborate on what the Freightliner bulletin is for. Are you saying they have had issues with their harness and they recommend replacement? Or is the subject something else? I can't believe they want to replace the entire brake harness from the front to the rear of the chassis.

I have a 99 Dutchstar Freightliner Chassis. The grounds on the brake lights and other lights in back corrode and loose connection. Check the connections by removing the light assembly. The grounds just fall off. 13 yrs. of hwy. not the harness but a simple loss of ground.

You can check out the Roadmaster web page. They have diodes that go in the brake and turn signal lines, They a commonly used to protect the coach circuits from shorts when pulling a toad. That helps keep from blowing fuses and trying to find them. At time it keeps the coach lights working even if there is a problem with the Toad or interconnect harness.

I made some inquiries and I believe you need a third number on the end of your part number (06-28598-00?) if it is a '0' then it is a good part number but is hard to find. Such a wiring harness will have both tail, turn and stop lights in the same harness.

If you have a connection on the rear of your coach to connect you toad, connect your toad and see if you have brake light on the toad. I don't believe you have a ground problem because if you did, none of your tail lights would work. I am basing this on the fact that most Tail and Stop lights are in the same bulb.To check for a ground remove the bulb and check the rim of the connection to known ground on your coach. If you have continuity then you do not have a ground problem.

R.M. I have never heard of diodes in a vehicle wiring harness (of course I learn something new every day). I do know and have diodes on my toad (I wired them in myself) to keep the reverse current from flowing back into the toads computer (big problems if that happens), but not in my coach.

I have no power to the starter solenoid. I have replaced the switch but that wasn't the problem. The solenoid on the starter works OK and I have rigged a switch to the battery to start the rig. I am told there is a second solenoid that the switch triggers which In turn triggers the one on the starter.

Too hard to troubleshoot via keyboard. You need to start chasing wires. Shotgunning parts at it is going to get expensive, fast. Your neighborhood Freightliner dealer should be able to get a wiring diagram for your specific truck, or get you access to the database, then start following wires.

While I am not experienced with the chassis that you have, a relay that is operated by the ignition switch to supply power to the starter solenoid is not an uncommon thing. You should be able to locate it by tracing the heavy power cable back from the solenoid toward the battery to find it. It should look something like this.

I have a kenworth with a Cummins n14. I have a relay on the dash that I removed and connected a push button start switch on the dash. I think the actual problem is a switch on the transmission. If you think it will help I can take some pics tomorrow. It is in storage right now.

I had thought of a push button to start and it might come to that. I really am not throwing parts without thought. I didn't know there were 2 solenoids. I determined the one on the starter was good. Talking to Freightliner about this, they didn't tell me about the second solenoid and after all the tests I did, they said it had to be the ignition switch. Well it wasn't then someone told me about the second solenoid. I ran a wire from the battery through a switch to the starter solenoid to get started. That works well except I have to go outside to the battery to start. Sure beats sitting along the road tho.

With a long run you probably have a small wire going from the switch to the presumed solenoid or relay then to the starter solenoid. Have you tryed a helper to activate the switch well you search, often a relay will still click but not carry juice. You can always run a wire from the switch your self. Have you checked to make sure the switch is getting power and is sending it out to the starter? I had one that would run all the excessorys but not the start position. Although it sound like a relay. A second relay would probably not be a Cummins item but an Allegro part.

Thanks again. I have a few days if other things to do but will try some things mentioned here. I think this is all Freightliner because Tiffin buys it ready to do. Even the dash is installed. I don't have much faith in Freightliner. They told me the part number I needed. I found it to be an obsolete item but found one at a dealer in Nevada. Cost $100. Not even close to the right part. Right one was about $30.

The wiring diagrams from Sparton (I know your on a Freighliner but perhaps wiring is similar) show multiple relays/solenoids in the starter "path". One is controlled by the Allison to lockout the starter if not in neutral. You really need to get a wiring diagram and start tracing wires (and I need to do the same!).

1. Bad battery or low charge, or bad connections at the battery terminals. If the terminals are full of white snowy looking stuff disconnect them and clean them up. If a terminal is loose (you can turn it with your hand) tighten it. Check the battery voltage. A fully charged car battery would read about 12.6 VDC. 12.3V is 50% charged. Less than that and you will quite often have a starting problem. Even if the battery voltage seems OK you should try jumping the truck to see if it'll start - a failing battery may have a reasonable voltage readout but very little capacity available, making it unable to start the vehicle.

2. No power to the starter motor or a defective starter motor. What's called the "starter" has 2 power connections - a large wire that provides power to the starter motor, and a smaller wire that powers the starter solenoid. When the key is turned to start the solenoid will engage the gear on the starter with the ring gear on the flywheel as well as trigger the starter motor to begin turning. If there's no power to the starter motor but power everywhere else you'd hear a "click!" noise when you turned to start but nothing else - ie. no whirring or cranking noises. If you don't hear that click (you might need someone to stand outside with the hood up to hear it) go to #2. The cause of this problem is usually one of 3 things - a failed starter motor, a bad connection between the battery and starter motor, or a blown fuse (if present) in line between the starter and the battery. A test for DC voltage between a ground point (eg. battery negative terminal or the engine block) and the large wire on the starter can diagnose a blown fuse (it will read 0V) but it can't be used to indicate if the connection or starter are ok. The simplest way to diagnose that problem is to clean the battery terminals and the large starter terminal (MAKE SURE TO DISCONNECT THE BATTERY + TERMINAL BEFORE DISCONNECTING THE STARTER CABLE OR YOU COULD GET A SEVERE BURN). If it still isn't starting take the starter off and have it tested (you can test it yourself if you can mount the starter somehow so it won't jump, connect jumper cables to the battery with the - cable going to the metal body/frame of the starter and the + connected to the big starter terminal AND the small solenoid terminal at the same time - but be forewarned that if the starter isn't firmly mounted it'll jump like crazy and can hurt you!).

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