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Just got a 2001 F-250 Super Duty (crew cab, long bed, 4x4, 7.3L turbo diesel) and have been going through and fixing a lot of little issues. The one that now has me stumped is the interior lighting circuit (which is also the bed light). Here's what I've got so far:
Map/reading lights work, but dome lights do not (neither automatically nor when turning them on via the dimmer switch).
Verified all fuses in the PDC as well as the interior fuse panel (behind the driver side knee panel). The interior lighting relay was missing, so I purchased and installed it.
Relay #1 (interior lighting), fuse #4, and fuse #14 are all good - when I pull the fuse with the door open, the relay clicks (and clicks again upon reinstalling the fuse). With the doors closed, the relay clicks when activating the interior lights via the dimmer switch.
The LT GRN/YEL wire is hot, and all related accessories work (map lights, engine bay light, etc).
The BLK/LT BLU wire is not receiving power from the relay from what I can tell.
Before I start trying to pull out the fuse panel to start checking connectivity, do you guys have any tips on anything else to check? The ground at the rear driver corner of the cab is good, and a visual check of the harness running down the driver side of the cab has no visible signs of damage.
Also, given that the relay is audibly actuating the way it should, I'm guessing that the GEM can be ruled out as a possible cause?
My next step will be to get a pinout diagram for the relay and crimp a quick jumper to see whether or not it's simply a defective relay... But I doubt it's the case.
Pulled the relay and jumped the two parallel vertical contacts on the fuse box side (which is supposedly the load path) and got nothing on BLK/LT BLU. I'm beginning to fear that it's either a bad connection in the panel itself, or the GEM is in some way responsible for providing power to said path.
Flargen, According to the 2001 schematics (see below) there are two relays involved. Both appear to be mounted on the instrument cluster. From what you say, the "Battery Saver Relay" is picked because you have 12V on the LG/YE wire. However, the "Interior lamps relay" needs to be picked to supply 12V to the BK/LB wire. According to the schematic, it is picked either by the "Main light switch", or internally on the cluster board by the Microprocessor".
First, be sure fuse 41 is good in the CJB. Next, check to be sure the light switch is providing a ground on pin 8 of connector C270a to pick the relay. Then check to see if you have 12V on pin 2 of connector C220c when a good ground is on pin 8.
This troubleshooting will show where the problem lies.
Thanks a ton for the thoughtful reply - unfortunately, I think that might be for a different year or model... To my knowledge, there are only 2 fuse/relay centers: the one under the steering column behind the driver knee panel (the Central Junction Box), and the one near the driver side firewall in the engine bay (the Battery Junction Box). Both of them have fewer than 40 fuse/relay spots. This is going off the electronic FSM I was given for the truck, as well as physically inspecting them.
Is there another one I'm missing?
I also can't find any reference anywhere to a Battery Saver Relay in my docs.
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