Need a wiring diagram for a 2000 Kenworth W900L

http://www.bbbind.com/free_tsb.html free wiring diagrams , fuse box lay out etc....

Good question. Since most manufacturers don't give routing of harnesses, just generalization. Where they should be. You have to do what most of us do. Pull panels to find the short. Start at the light itself. Check for power and ground in the wire behind the plug.

check for a fuse for that control switch if it controls power
it may be a switch that moves valves to allow air to the vent actuators check for air line connections
talk with a kenworth service centre.

You mean by gadgets, warning lights and gauges? That would be from the ignition switch's run wire, the wire from the on position. This wire sends voltage to the ignition system, and to the dash for the warning lights and gauges-but not directly to the dash-the signal would reach the dash after being routed through the fuse panel to a fuse for the dash gauges and warning lamps. You need to check if that fuse is good.
Recall seeing any wiring diagram? The fuses are labeled either "hot at all times" or "hot in run or start". The fuses labeled hot in run or start are only sent power when the key is on, so power for those fuses are routed through, or turned on by the key being on. Depending on the car and its wiring set up, many will have relays that are turned on by the run wire, and power is then sent from the relay to that circuit's fuse in the fuse panel. This relay may be called the ignition relay. Or your car may have a different relay to send power from the run wire to the fuse panel.
The only way to figure yours out is to see a wiring diagram for it. Then you will see how power is sent from the ignition switch to the dash.
Wiring diagrams are almost always found in repair manuals. Check if your library has a manual for your car. Most libraries have quite a few repair manuals. Or parts stores sell repair manuals too, for about $25. Try to find a Haynes repair manual for your car. The other popular repair manual is from Chilton. My preference is Haynes, just my preference. I been burned by Chilton manuals sooo many times-incomplete wiring diagrams, incorrect information, incomplete information. Haynes are not perfect by any means, you want perfection-spend big bucks for a factory service manual ! In general, Haynes is more complete than Chilton.
OK, enough venting. If you have a test light, check for power at the fuse for the dash (may be labeled "gauges" or "instr pnl", something like that) with the key on. If it has power with key on, wire from the fuse goes to the dash. If that fuse has no power to it with key on, power has been lost between the ignition switch and that fuse-now you definitely need a wiring diagram to find the problem.

I am sorry but fixya has no wiring diagrams. The reason is that they are copyrighted and not free to share on line.

Do NOT Cut and Splice. Your local parts store sells an aftermarket radio plug in which connects to your factory harness and then you can splice in your radio into the new connectors ends that are labeled for what they go to.

ok its easy, first see the stereo installation diagram, but i think its have spare wire harness, try to find it. inlay your wire in secured area, dont forget to install fuse in acc and in hot at all time(constant 12V)

First. I would go to the library and pu a chiltons/moter
or mitchells repair manual with wiring diagrams. Then
I would put the wiring back to factory specs. Then I
would deal with the problem that caused somone
to mickey mouse the light wires. It may be a headlight switch/dimmer switch or the drl module
(daytime running lights) maybe a short or bad conn.
But I can't tell you with any degree of accuracy,
what to check to diagnose the problem you're having.
With the wiring the way it is and not able to see it.
As for whats happening now, check any taped connections for a short also you'll need to replace
the melted socket. But when you install the socket
also install a 20amp inline fuse to the +power wire
to the socket. This will help avoid any more meltdown
until you're ready to wire it back to normal, just keep
some spare fuses handy. Free food for thought.
Good luck.

I found a couple of web sites that may be able to help you out. truckmanuals.com advertises KW manuals based on model and serial number in the $500US range. There is also another web site that will provide service manual info to on-line people to make their own repairs( I suspect there is a fee involved). It is cittrucks.com. Hope this helps.

This is a common problem on 97-00 MY trucks, regardless of the trim level ( XL, XLT, Lariat ).

If you install the fog lamp fuse in the BJB ( aka Battery Junction Box, Engine Compartment fuse panel ) Fuse # 9 ( 15 A fuse ) and jumper the normally open contacts in the fog lamp relay socket ( see diagram below ) the fog lamps should illuminate ( to confirm what you have doing on ).

The problem usually is the main headlamp switch to the BJB is not in place ( this is the yellow wire from the main headlamp switch connector to the relay socket pin #1 ).
One easy route is to make an aux lighting relay & harness, or purchase one online. With this, you can cut the factory ends and attach them to the harness you purchased. There is an air inlet next to where the steering wheel column runs through the firewall. This would give you an easy route to the fog lamp switch. The fog lamp switch, you can buy the factory one, and change the yellow wire from the connector to your added relay, or just add a switch for this function.
This will give you an idea of what the DIY relay and harness would look like.


Hope this helps, more than confuses at this point