The wiring for the turn signals are very confusing. It does things that just do not make sense. I have posted this previously. From the Ford Manual. DESCRIPTION AND OPERATION DESCRIPTION The parking, sport, rear, side marker and stop light circuits are controlled by the headlight switch. When the headlight switch is pulled out to the first detent, only the parking lights and side marker lights come on. When the headlight switch is pulled out to the second detent, the parking lights, side marker lights, headlights and sport lights on vehicles so equipped all come on. Maverick requires activating a toggle switch in conjunction with the headlight switch for sports lights. On all vehicles except Mustang, the side marker lights also function as emergency flashers. The side marker lights on Mustang do not flash. OPERATION On Thunderbird, Ford, Mercury, and Lincoln Continental a cornering light bulb is in the same light body with marker bulb on vehicles so equipped. The cornering lights are fed from the turn signal circuit in such a way that when the turn signal switch is activated, the cornering light on the turn side will burn with a steady glow. All Vehicles Except Mustang The side marker lights are connected in parallel with the feed circuit (from the headlight switch) that feeds the minor filaments of the front parking and rear lights. Each of the four side marker lights (two on each side) completes its circuit to ground through the dormant major filament of its respective left or right front parking light. Therefore the side markers glow with the parking lights. The side markers are on when the parking light major filament is dormant providing a ground as described in the foregoing. When the turn signals are activated however, the major filament of the turn-side parking light is fed intermittently for turn signal operation. This intermittent feed interrupts the side marker lights’ circuit to ground causing them to go off. As a result the affected side markers for the direction of turn selected will flash alternately with the front parking/turn signal lights. The side markers on the opposite (non-turning side) will continue to glow steadily. The turn signal system supplies an intermittent feed to the major filament of the turn-side parking light as described in the forgoing. The same circuit also supplies and intermittent feed to the side marker lights (on the turn side) but flowing in a reverse direction from that supplied by the headlight switch when it was on. The two side marker lights complete their circuit to ground through the dormant minor filament of the turn-side parking light. Thus the side markers and front parking lights flash simultaneously with each intermittent feed. The lights on the opposite side remain off. The emergency flasher sends intermittent power to the major filaments in both parking lights, thus interrupting the ground circuits of all four side markers. As a result, all four side markers will flash alternately with the parking lights. So, make sure all of your bulbs are good, including dash, and they get a good ground. If this does not fix it, I would suspect the turn signal switch Micah
you need to figure out where the power is entering the light system. the most likely place is the dash cluster. i would unplug the cluster and see if the rest of the lights turn off. also are the lights on all the time or only when the key is on?
Is is just one ground on the front and one ground in the rear? I replaced the turn signal switch this afternoon but no fix. If its the dash cluster how would i go about fixing it? Also, the lights are only lit when the key is on. I have the ford shop manuals, would it have information on this problem?
pull the instrument cluster out and unplug it. turn the key on and see if the running lights still turn on. i bet they wont. if the do then ignore the rest of this. now you need to find the ground wire for the instrument cluster and check that it is getting ground. this can be done with a test light, voltmeter, or ohmeter. if it has ground then you need to look at the printed circuit on the instrument cluster and find where the circuit is broke. i suspect you will find the ground wire is not grounded.
I unplugged the instrument cluster and as you said it turned the lights off, ive been searching for the ground but shes hard to find. How would i be able to tell which circuit is broken, using s test light as well?
AND the light bulb just came on, or out, whichever... What's the possibility it has a later cluster installed??? I know some of the PCB traces are in different locations between early vs late and signal light ground appears to be one of them... Anyone know result of incorrect cluster install???
you need to find the wiring diagram and the interment cluster diagram for your year car. i can never remember who it is but member has a site that has all of the diagrams. the site is something like 1badfalcon or something. im sure someone else will post a link to it. with the diagrams you can find which wires are ground and then take a test light hooked to the positive battery post and touch it to the ground terminals in the connectors that plug into the cluster. the light should light up. i dont think it i will. if it doesnt then you need to follow that wire to where it is supposed to be grounded and make sure its properly grounded. paint under a ground can cause it not to get ground.
