Tail Lights And Guage Cluster Lights No Longer Working

Discussion in 'Fox 5.0 Mustang Tech' started by omar2006, Jun 14, 2013.

  1. 90 Mustang GT. When I turn on my headlights they work fine along with the fogs. But my tail lights do not illuminate unless I press the brake pedal. Also the gauge/instrument panel lights stopped working. Kinda need both these things to function if I plan taking my girl out tonight!

    I checked the headlight switch connector (http://www.latemodelrestoration.com/item/LRS-14489A/87-93-Headlight-Switch-Connector-Assembly) as some other threads and other forums have said to do. It was fine. No burns or anything.

    Not sure what else it could be. I'm not very savvy with electronic wiring. If anyone has any ideas or areas to check I'd appreciate it. I'm home all day today so I'd like to tackle this problem.
  2. I'd be suspicious of the switch. If there was a diagram of which wire had the power to these things it would be fairly easy to check.
  3. The headlight and fogs work just fine. If the switch were bad wouldn't they no longer work?
  4. Unlike a wall switch, there are several contacts in this type of switch. Making sure it is putting out all the right volts is a logical place to check. If I do not know, I will not just make it up and waste your time. The dimmer for the dash lights could be toast and everything else work. The old ones were a coil of wire and a moveable contact to wear out. The whole switch could be falling apart like someone's ignition switch on here. Unless he got it replaced, that switch has a boatload of exposed contacts. I just wish I could tell you what color of wire to look at.
  5. I will not lead you wrong on purpose and waste your time. This is not like a wall switch with one circuit to run. There are multiple contacts that could have problems. I hope someone has the wiring diagram to tell you what color wires should send the right volts. Also, the fuses would be cheap and easy to fix.
  6. Replaced the headlight switch. No change. Also checked fuses again. Anyone have any other ideas?? Headlights and fogs work just fine. Tail lights only work when pressing the brake pedal. Reverse lights work, emergency lights work, turn signals work.
  7. Took out the dash and immediately saw there was a green/whitish powder-like residue around the dimmer switch. I suspect it's that. Tomorrow I'll clean the switch up with a brush and electrical cleaner tomorrow (new switch goes for $100!). Hopefully that's the problem. If not, I'm out of ideas.
  8. Some of those lights run on different circtuts and switches so that they work is only a little help. Sorry. The cost of the switch is the reason I asked if anyone had a body wiring diagram. My Haynes manual has chassis diagrams in chapter 12. I hope one picture would help, and the library might even have one to examine. After cleaning the switch and checking the contacts, to this manual is where I would head!
  9. By the way, mice happen. The dumb things like to chew on wires. You really need the diagram to start chasing if power goes to the right places. I had a Fox body Cougar they filled the heater core with loose fiberglass one winter, and was using the car daily.

    Anyway do not waste money until you get the right diagram and use the meter. It could be a broken wire or fuseable link too.
  10. I broke the springs out trying to clean out all the corrosion in them. Was forced to buy a brand new switch because I bent them all to hell and couldn't get them to stay in. Anyway, the new switch came in the mail today and I installed it and began to put the dash back together.

    Now I have a new problem (or a continuation of the same one). When I turned on the headlights to make sure the taillights are working properly, it immediately blew the fuse. The fuse I'm talking about is the top left, 10 amp fuse. So I replaced it thinking maybe as I installed the new dimmer switch that it shorted out. Checked the lights again and it blew immediately. It even sparked. Tried a 20 amp fuse just for the hell of it. Blew that too just as fast.

    Any ideas what could be shorting out the fuse? I'm going to be relieved as hell when I figure this whole mess out!
  11. ignition switch on the column... pull the cover off and check it . they are plactic and metal and after some age the plastic starts to pull away and the switch will start to seperate... sometimes you can tiewrap it for a temp fix but the switch is cheap to replace .. when they do this it can cause lots of electrical problems including torching the harness.
  12. I sympathize with your problem, but I don't understand why you put a 20 amp fuse in place of the 10 amp. That fuse is there to keep you from frying things with too much amperage.

    Checking the ignition switch on these cars is always a good idea, and they can cause strange problems. Start with that. If it is okay, then you need to start tracing wires. I suspect a wire is grounding out against the chassis somewhere, so closely check anywhere where the headlight and tail light wiring passes through a hole in the sheetmetal.

    A wiring diagram would really help to know exactly what wires are in that circuit.