Electrical Problems

[w.lawhorn]

Let me start by saying that I am new to the forum, and this is my first 7.3. I am pretty familiar with the mechanics of the powerstroke drive train and engine. I have bought a truck with a few problems but this is the first one i want to eliminate.

The instrument cluster illumination, climate control illumination, overhead display, and 12v power point do not work. I believe they may be related. It doesn't seem to be a fuse as I have checked all the related fuses. All the idiot lights and gauges work. I am not very familiar with Powerstroke electrical systems.

2003 Ford F250 Lariat 7.3PSD SC SWB FX4 Bone stock, for now.

[w.lawhorn]

So I guess this isn't a common problem?

[lug]

Your climate control, instrument cluster and overhead console all get their power from the same light blue/red (LB/RD) wire coming out of the light switch, but they go to two separate ground wires. The power wire (LB/RD) goes to a splice (S216) and spiders out from that point to the items I listed plus a few others like the 4wd mode switch, radio, speed control/horn switch. The 12VDC power point is controlled by a 20A fuse (#10) in the Battery Junction Box. Both ground wires go to a shared ground point under the I/P near the center. I would bet you'll find those ground wires loose, disconnected or broken. Since you verified the fuses and the power point does not share a common power wire your best bet is the common ground point. All the idiot lights and guages receive power and ground from other wires which is a good thing.

[w.lawhorn]

Thanks for the reply, I actually went back and checked the fuses with a ohmeter and the PowerPoint fuse was blown. I am going to check it and see what's up. If that is the case my radio works but my 4wd switch does not. I think whoever put in the after market radio might have messed up the wiring. I will find out and post it for future reference.

[w.lawhorn]

So I looked at the radio wiring and it is wired to a constant hot obviously. The lb/rd wire is not hooked to the radio, but it is back there so obviously this has been a problem for awhile. The dimmer is connected so I guess I need to see if there is continuity between the wire at the radio and the grounds well as between the connector on the dimmer and the wire at the radio. If the wiring is fine it must be the dimmer switch. That can be verified by back probing the LB/RD wire at the switch. If there isn't voltage it has to be the switch, or before it.

[lug]

If you decide to cont. out the switch put the wheel in its detent (full bright) and turn the headlight switch to park or head, either will work. Go to pin 10 to pin 5 and you should get continuity. This path is the power route from white/red (WT/RD) wire through the switch and exits at the light blue/red (LB/RD) wire. You can check pin 12 and 4 for the dimmer wheel. Detent is closed circuit and turning the wheel to the opposite extreme should yield an open circuit. That white/red wire goes to the Generic Electronic Module (GEM) which is tucked up under the I/P to the left of the service brake. Another continuity check, if your still tracking, is pin 10 on the Gray main light switch connector to pin 17 on the GEM connector which should be the biggest of all the connectors with 26 pins. At this point you should have found your problem, if not then I would check the splice mentioned previously to make sure some 'genius' didn't cut the wires and tape them up.