Everything but the Tail lamp. Help needed.
 

'99 Discovery II that I inherited. I love this vehicle but it has had a lot of problems, the most recent of which is an issue with the tail lamp. The driver side tail lamp does not work. Just that one bulb doesn't come on when I turn the lights on. Brake lights work fine as does all other lights aside from what appears to be a burned out "city light" in the driver side headlight.

Now I'm not one to post a question immediately and I've been digging through these forums all day trying any solution that even remotely relates to the problem. I've changed the bulbs, checked to make sure they were the right ones and also compared them to the passenger side bulbs. Checked all fuses in engine compartment and passenger compartment. Checked what appears to be a common ground under the rear of the vehicle, cleaned it with a wire brush and reattached it. Checked the grounds on the harnesses inside the "vent" removable plates in the cargo area and I've tried bending the metal bulb socket in the bulb cluster out for better contact and used some bulb grease. There appears to be no corrosion or sign of leakage. I've removed the interior panels from the driver side up to the back seat and all wires appear in good condition as do all harnesses.

So now I'm turning to making a post as I'm not very experienced but I've taken a liking to fixing this beast on my own. I'm really not able to fully understand the wiring diagram in the RAVE aside from following it to the light as I'm unable to relate it to my vehicle. Guess I'm just too new at it. So is there anything that I'm missing? There is a trailer harness for my trailer but it seems to be working fine as usual.

Any help at this point will be greatly appreciated by both me and my aching back. Thanks in advance

OK, let's look at the wiring diagram in the circuits manual from the RAVE. Attached.

See the wire marked RB (red/black) that goes to the tail light? There is a tiny number on the drawing that shows the connector number and the pin for that wire.

The connector number can be found in the electrical library section of the RAVE, and has a picture of it and colors again. You will note that the Discos in these pictures are the cleanest on the planet. So you can unplug that connector and attach your test light or meter between pin 3 and ground, looking for 12 volts (actually, more like 13 and change). You can also meter pin 2, the black wire, for ohms to ground (should be about a dead short to ground).

Most tail light problems are from corrosionon the metal that mates with the base of the bulb in the socket.

Thanks!
 

That succinct and simple explanation has helped immensely in reading the chart. The chart you linked shows two 10 watt bulbs but my tail light has 4 bulbs in it. A tail lamp at the top, a brake lamp in the middle which is the same bulb and two smaller bulbs at the bottom for the reverse light. The connection to the cluster only goes on one way and in a stroke of genius, or maybe stupidity, I thought "What if I connect the passenger side cluster to the driver side connector?" The reverse lights at the bottom should come on as the tail lamp would correct? Or will my D2 explode?

If that works then it would be the connection at the bulb since I know all the bulbs work as I've tried them in the sockets that do work. Strange though as the socket appears to be very clean and in great shape. Still, I traced the ground wire to a clip that fits two wires inside and bites into the rubber sleeve. The second wire into that connection is the ground that runs under the rear bumper and connects to the frame, a connection I cleaned thoroughly at the start of this whole fiasco. So I'm thinking it looks more and more as if I need a new tail cluster or that particular bulb isn't getting power for some reason. I appreciate the help and promise to post my solution when I find it.

The connection plate and or the socket has probably failed which although not common, does happen.
Start with inspecting and cleaning the socket for corrision, if that doesn't fix it but with a test probe, you find power to the connection plate, then you need to replace the plate assembly .

i had a similar problem with the bulb making intermittent contact with the tab that is inside the socket, i just bent it a little more so that it makes 100% contact and problem solved.

The chart I sent is the one for the stop lights. There are separate charts for the hazards and turns, and another for rear fogs , etc. All of these charts, or diagrams, are organized in the RAVE under the circuits pages (separate from workshop and owners and electrical library). The RAVE has 1529 pages in the workshop manual, 705 in the electrical library, and 278 pages in two circuits manuals. And then there's the overhaul manual. And the owners manuals. And on some models entertainment and navigation. All free, link below.

Mike - Thanks for the reply that's going to be my next step once it stops raining and if I can find my probe. Just completed a move and my stuff is all over. I did clean it well with a wire brush even though it appears clean.

Jbarr - Thanks, it was easy to bend the metal tab at the bottom of the socket but I'm having trouble bending the two tabs on the sides of the socket out. As it is I've managed to make it so that it's hard to insert the bulb but I'm not certain if I've managed to move those two side tabs at all but rather just sort of elongated the rim of the round hole. I'll work on them some more and see if it fixes it.

Savannah - Thanks for that link. I had actually gone to that page from a post elsewhere before I originally posted but like the monkey I am I immediately clicked the D2 link and when I couldn't find that diagram I went back to searching the forums and google. I missed the service manual lower on the page which is probably what I should have clicked on. You got me on the right track for figuring out exactly what's at fault and as someone that's been unemployed for a year now and can't afford to throw money at different solutions it's been a huge help. Finally got a successful interview but I'll be leaving work just after dark so I'm trying to get this tail light issue buttoned up so I don't end up with a ticket.

I'll post back again with what I find as soon as I'm able to get out there and work on it.

Update:Solved.
 

Just wanted to make good and post a final post on my fix. I picked up a new tail light assembly today from a local salvage yard for $55. Popped it in and the running bulbs are working again. Now I'm going to tinker with the old bulb cluster to see if I can figure out why it stopped feeding power to the bulbs. I'd like to note that I did nothing more to the wiring or harnesses before installing the replacement so it was definitely my old tail light.

Thanks for all the help and advice.