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· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #1 ·
When I first got the Bronco, the dimmer would inconsistently dim if I turned the headlight knob. One day I came out and the dash lights didn’t work. I’ve had this before, so I swapped the switch. No more dash lights with the replacement. Later in the week, I discovered my brake lights were out, but rear lights still work.
I noticed the fuse for the dash lights was out, so I replaced it. No dice. The taillights fuse is also blown.

So, I got the wiring harness and swapped it in, and so now, what I’m wondering, is there anything else I should look at before I put those fuses in to see if it blows?

This truck doesn’t have the cruise control switch (even though it has cruise control) that’s on recall and leaks. The plug for the headlight switch was falling apart but no real burn marks that I could see.
 

· Premium Member
1986 Bronco Eddie Bauer 5.0 mostly stock
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2,641 Posts
Maybe the brake light switch under the dash on the pedal is bad? Causing a short? You didn't happen to ever swap to LED lights in your dash did you? Those can sometimes not gee and haw with the old dimmer systems.
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #3 ·
I hadn't thought about that. I'll take a look.
All dash lights are stock lights.
 

· Super Moderator
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33,587 Posts
Yo Marty,
Instrument Panel Lighting Dimmer Circuit Wiring Diagram & Testing in 92-96; "...The only significant difference between '92-96 and '80-91 is that the MFS's DIMMER switch replaced the older beam select switch, but they perform the same function..." by banned member Steve83

See
Section 13-00: Instrument Cluster and Panel Lighting
1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual​
DIAGNOSIS AND TESTING
Symptom Chart — Instrument Cluster and Panel Lighting
NOTE: Use Rotunda 73 Digital Multimeter 105-R0051 when performing the following pinpoint tests.






INSTRUMENT CLUSTER AND PANEL LIGHTING
ConditionPossible SourceAction
  • Control Illumination Inoperative
  • Fuse.
  • Headlamp switch.
  • Circuit wiring.
  • Instrument Panel Illumination Does Not Dim
  • Headlamp switch.
  • Instrument Cluster Illumination Inoperative
  • Circuit wiring.
  • Illumination bulbs.
  • Instrument cluster printed circuit.
  • Climate Control Illumination Inoperative
  • Circuit wiring.
  • Illumination bulbs.
  • Audio System Illumination Inoperative
  • Circuit wiring.
  • Illumination bulbs.
  • Single Illumination Source Inoperative
  • Circuit wiring.
  • Illumination bulbs.
@ 1996 Bronco/F-Series


Multi-Function Switch (MFS) Failure Causes; "...Mechanical components wear out or electrical connections are faulty; If the switch assembly is not operating properly, turn signals, hazard warning lamps, windshield wipers/washers and the headlamp beam selection may not operate properly. Related Components to Check; The switch itself, the electrical connections to the switch and the connections to each of the affected components (items such as turn signals, wipers, etc.)..." miesk5 Note; enter applicable info for year, etc. by Ford

Dimmer High & Low Headlight, Flash-to-Pass, Hazard, Multi-Function Switch (MFS), Turn & Brake Light Testing & Wiring Diagram in 92-96; "...the MFS testing is done with connectors disconnected; it's strictly an internal test of the MFS..." Miesk5 NOTE; Brake Light & Turn, Dome, High & Low Headlight Dimmer, Flash-to-Pass & Hazard CKTs are a Feed-Through Circuit in Multi-Function Switch (MFS).
Line Font Material property Parallel Rectangle



Font Material property Parallel Pattern Monochrome
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #5 ·
Just a follow-up. Replaced the brake light pedal sensor and no dice. Although it seems the fuse for the dash lights and brake lights aren’t blowing, still no brake lights. When I plugged everything back in, the hazard lights were on accidentally. This caused (it seems) the fuse for the brake lights to blow. Now I have no turn signals or hazards, but headlight and taillights still come on.

I haven’t gone through the circuit testing, yet. I do know that the multi-function switch (turn signal) is new but I don’t believe it to be a Motorcraft part.

anything else?
 

· Registered
88 Bronco XLT, 351w, c6 auto, 3.08 geared,
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110 Posts
Check all your grounds to your body, and the body to battery ground, stock grounds on these trucks are poorly implemented and after 30 yrs of exposure you should go around and clean and seal them
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #7 ·
I recently did this because of an issue with starting that I resolved with a new negative cable. I'll double-check if somehow I didn't tighten them correctly, but I'm kind of doubtful that would be it.
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #8 ·
Bringing this back up:

New multi-function switch (Motorcraft) is working well, but I only have the third brake light, no main brake lights. All other exterior lights work (turn signals, hazards, headlights/taillights). Dashboard lights still don't work. I'm guessing I'm dealing with some issues under the dash with the wiring itself?
 

· Super Moderator
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33,587 Posts
Yo Marty,
Are the Hi-Mount edStoplamps on Continuously?
PINPOINT TEST G: ONE OR MORE STOPLAMPS INOPERATIVE
G1 CHECK STOPLAMP SUPPLY AT BULB
  • Gain access to either stoplamp connector. disconnect stoplamp connector.
  • Using Rotunda 73 Digital Multimeter 105-R0051 or equivalent connected to a known good ground, check either Circuit 9 (LG/O) or Circuit 5 (O/LB) for voltage.
Is battery voltage present?
YesNo
GO to G2.SERVICE Circuit 9 (LG/O) or Circuit 5 (O/LB) for open circuit. RESTORE vehicle. RETEST system.
G2 CHECK STOPLAMPS GROUND
  • Using Rotunda 73 Digital Multimeter 105-R0051 or equivalent connected to a known good ground, connect second lead to Circuit 57 (BK) at either stoplamp bulb connector.
  • Measure resistance.
Is resistance 5 ohms or less?
YesNo
REPLACE damaged miniature bulb. RESTORE vehicle. RETEST system.SERVICE Circuit 57 (BK) for open circuit. RESTORE vehicle. RETEST system.
PINPOINT TEST H: STOPLAMPS/HI-MOUNT STOPLAMPS ON CONTINUOUSLY
H1 STOPLIGHT SWITCH CIRCUIT TEST
  • With stoplight switch in the OFF position, use Rotunda 73 Digital Multimeter 105-R0051 or equivalent to measure voltage at the output side of the stoplight switch, with Circuit 511 (LG) disconnected at splice.
Is battery voltage present?
YesNo
REPLACE the stoplight switch. RESTORE vehicle. RETEST system.REPAIR short to power at individual suspect lamp. RESTORE vehicle. RETEST system.


  • Instrument Cluster Illumination Inoperative
  • Circuit wiring.
  • Illumination bulbs.
  • Instrument cluster printed circuit.
PINPOINT TEST C: INSTRUMENT CLUSTER ILLUMINATION INOPERATIVE
C1 CHECK BATTERY VOLTAGE SUPPLY
  • Pull headlamp switch into PARK position.
  • Rotate headlamp switch knob and shaft fully clockwise without turning on courtesy lamps.
  • Measure voltage with Rotunda 73 Digital Multimeter 105-R0051 or equivalent Circuit 19 (LB/R) at IP fuse panel.
Is battery voltage present?
YesNo
TURN headlamp switch to OFF position. GO to C3.GO to C2.
C2 MEASURE VOLTAGE
  • Measure voltage at feed side of instrument panel fuse.
Is battery voltage present?
YesNo
REPLACE fuse. RESTORE vehicle. RETEST system.SERVICE open or ground short in IP fuse panel battery feed. RESTORE vehicle. RETEST system.
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #10 ·
The main brake lights don't come on at all. Bulbs flash properly, which is the same filament on the bulb that is the brake. When I hit the brake pedal, only the third light comes on.
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #11 ·
Here is where I am at. I have all lights but the main brake lights, but if I hit the brake it blows the 15amp fuse for the hazard/brake/turn signals. I’ve replaced basically any parts, so this has to be wiring. Where should I look?
 

· Registered
1993 Ford Bronco
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126 Posts
Discussion Starter · #13 ·
Ah ha, there is exposed wiring going to the brake switch. It’s right by the connector so I ordered a connector. Should have it this afternoon from O’Reilly’s warehouse. Will report back!
 
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