External Lights Troubleshooting

Asked by Nov 22, 2016 at 01:43 PM about the 1990 Ford F-150 XLT Lariat Extended Cab LB

Question type: Maintenance & Repair

I own a 1990 Ford F150 XLT Lariat.  I've owned and DIY repaired quite a few different makes & models of vehicles.  This truck is the first Ford pick-up I've owned.  I bought it two years ago from the original owner.  I've had very little trouble with it...until now.  Even though I have an electrical engineering degree and can troubleshoot just about any kind of electrical/electronic circuit if I have a schematic, auto electrical systems can still be kinda quirky.  Anyway, here's the problem that popped-up two days ago:
With the headlight light switch in the full on position, neither of the front amber parking lights nor the two tail lights will turn on.  The hi/lo beam headlights work properly, and the rear brake lights, and white back-up lights all work correctly.  Further, the front & rear turn signal lights in both the turning position and in the emergency flasher mode, work properly.  I pulled & continuity checked all of the fuses in the fuse panel on the lower left of the steering column, and none are blown.  I have a Haynes repair manual, but, it's not detailed enough for me to pinpoint the source of the problem.  I don't want to take it to a mechanic & pay a ridiculous amount of money to get my parking lights & tail lights functional again. I am obviously missing something, but, cannot find a more detailed troubleshooting guide on the internet.  Maybe you can help?  Thx!  Steve...Seattle, WA

3 Answers

18,270

I'm pretty good with electrical problems myself, but vehicle manufacturers do the best they can to save three feet of wire anywhere possible. A color coded wiring diagram is what is needed. What I did was contact ALLDATA, and part of Autozone and asked if their repair manual had a color coded diagram for my 2010 F 150. It costs about 25 bucks a year for an online subscription for all aspects of repair. It is year and model specific and you'll have to enter your VIN to get all the info for how your vehicle was assembled. Call first to make sure the color coded wiring diagram is included. It's a step-by-step repair catalog and has testing procedures to locate the problem. Mych better than Hayne.

1 out of 1 people think this is helpful.

Much obliged OJ! Being a baby boomer, no self-respecting teenage boy in that generation could not wait to get his first car (and not necessarily with a driver's license, first!), and auto shop classes in high school were a given for all of us. Back then, however, cars/trucks were actually fun to work on...but, anymore, the "fun" meter has run out, and I can no longer contort myself into a pretzel to get under a dashboard, nor hang over a car fender for hours on end without taking a mouthful of Advil before & after! Thanks for your feedback, and you're right, the Haynes manual barely goes beyond the basics of an owner's manual. I'll mull over my options during the turkey day weekend, and decide whether my patience in screwing with it, or my bank account is the stronger of the two! Ciao!

18,270

Being a boomer myself I know exactly what you are talking about. As far as fitting in places and hanging over for hours. Yesterday I tackled a complete brake and shock replacement on my 99 explorer I am rebuilding, every part imaginable. Started with the calipers, rotors, pads, even the brake lines. Worked my way up to the master cylinder and booster. Learned quickly my body would not fit between the seat and the firewall so I could remove the four bolts holding the booster to the car. #$%^%$#! The wife came into the garage asking what was wrong. Simple I said. I'm 66 years old and gained about 50 pounds since I did this the last time. Additionally, my body doesn't twist like it use to, not without a visit to the chiropractor. Quickly came to the decision replacing that part wasn't necessary.

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