Fix For Dim 71 to 73 Mustang Dash/Instrument Panel Lights

[Ron Tanzi]

The circuit breaker on the starter relay on mine is for the rear defroster which I never use.

Ron

 

[mrgmhale]

I have a question regarding the thick black wire w/ silver hash marks going to the 20 amp circuit breaker. I believe mine is severed just outside of the firewall and there is no black/silver wire at the breaker. Does anyone know what this wire is for?

Here is a snippet for 1973 Mustangs showing the circuits involved with the convertible top. I see no reference to a black wire with silver hash. The convertible top circuit (175) is black with yellow dot. Please not the schematic shows the fuse block incorrectly feeding the convertible top circuit. I annotated it with corrections.

It is late at night, my eyes are going buggy, too buggy to do a lot of deep searches on the black wire with silver stripe issue. If the attached file does not help let med know in this thread and I will look deeper. We have two 1973 Mustangs, a Mach 1 that has had a lot of work done (properly from all appearances, no hacking) to it by previous owners over the years, and an almost untouched convertible with an incredibly low 21,000 original miles (barn stored over 40 years). If need be I can look at the wiring on those to see if I find anything like what you are sharing. I do not recall seeing black with silver striping on our Mustangs.

For unknown reasons (yet) one of the snippets shows Circuit 175 correctly feeding the seat back latch relay circuitry, then goes on to feed the convertible top switch. The other schematic has nothing about the seat back latch relay. Having just now noticing the conflict I am going to dig into this a bit more this week just for my own (in)sanity if no other reason. It is possible the schematics without the seat back latch relay circuitry is from 72 or 71, where it is possible the seat back latch relay may not have been available until 73. I will find out. Meanwhiel, I hope the file snippets are helpful.

 

[mrgmhale]

Folks,

Another great way of making your dash and headlight brighter is to install a headlight relay. Your headlights pulls juice through the instrument cluster and this keeps the headlight power going straight to the battery. It's an easy install that takes 1-2 hrs depending on how anal retentive you are on wiring.

I also removed the blue defusers. LEDs are good but generally don't allow you to dim the lights (may or may not be a big deal). You can get blue LEDs which look pretty close.

KR

I installed some RocketMan mini headlight relays on both of our 73 Mustangs, but not to increase the brightness of any lighting. Rather, I decided to install a set of Halogen bulbs to replace the oem sealed beam units. The Halogen bulbs use more current than the sealed beam bulbs, and I did not want to send more current through the headlight switch's internal circuit breaker. So, in general, I use the headlight switch voltage as the trigger current for the headlight relay, and let the relay carry the higher amperage load for the lights. That one was straightforward enough for the 73 Mach 1, but for the 73 Convertible I did something a little different. But, first, the Mach 1 circuitry is covered, then the vert.

In the 73 Mustang Mach 1 I installed a set of LED taillight panels (also in the Convertible, but those are Vintage LEDs). The LED panels in the Mach 1 were from a purchase earlier than my purchase from Vintage LEDs for the vert. There is a difference between the Vintage LEDs (www.VintageLEDs.com) and other manufacturers of LED taillight panels. For the LED panels in the Mach 1 I initially purchased, in order to have sequential turn signal flashers work as desired, I needed to provide a switched 12 volt circuit that would run to both LED panels, otherwise the turn signal flashers are non-sequential, just like the stock lights. I used a Buss fuse tap (https://www.amazon.com/AGC-Glass-Fuse-Tap-Adapter/dp/B07PXFVHGF/ref=sr_1_138?crid=2TIVHYAZ71L4P&keywords=buss+fuse+tap&qid=1670208054&sprefix=buss+fuse+tap%2Caps%2C78&sr=8-138) on a switched circuit from the fuse block, attached on the fused end of the fuse, and ran a 14 gauge wire to the trunk, under the driver side rocker panel carpet and trim strip, and under the rear seat plastic covers. I use the same switched power for the rear backup camera circuit (Garmin Drive 52 GPS with "wireless" backup camera, where "wireless" means for the video signal). So, the switched circuit I ran was doing double duty, LED panel power for sequential turn flashing capability, and to power the backup camera circuitry.

For the 73 Mustang Convertible I decided to do something different for the rear LED panels. I found out the Vintage LEDs did not need any outside power, as it has microprocessors on each panel that manages the sequential turning flash rate! But, I still needed power in the trunk for its backup camera circuit. And, although not particularly hard to do, I decided to not run a separate switched circuit from the fuse block to the trunk. Instead I used the Throttle Position Solenoid circuit (#640, Red with Yellow Hash) to trigger the headlight relay. Then I made certain the parking lights would be on any time the headlights were on. Normally, when the headlights are turned on via the headlight switch the parking lights are also on. But because I was using the headlight relay to activate the headlight circuit I had to power both circuit 14 (parking lights) and circuit 13 (low beam headlights) by splicing circuits 13 and 14 together. So now any time the car is running the parking lights and low bean headlights are on. The headlight dimmer switch on the floorboard does nothing unless the headlight switch is turned on. In high beam mode the high and low beam elements are now lit at the same time. I did this, rather than light up only the parking lights via the relay because in at least California the parking lights are not ever to be used without the headlights if the car is moving. I am not certain what other states' legislation requires, so I played it the safe way. When I replaced the rear taillight panels one of the two original 1157 bulb sockets was no longer needed for both the left and right taillight panels, as the taillight circuit on both left and right sides now uses only one of the 1157 sockets for the LED panel circuitry. So, using the original and now unused 1157 socket wiring I simply spliced into the parking light circuit #14 wire to feed the backup camera circuit. Had I needed the power for the LED taillight, using a brand other than Vintage LEDs, I could have used the spliced circuit 14 wiring from the now unused 1157 socket for that as well, because the headlights, and taillights, are now on any time the ignition switch is in the Accessory or Run position.

 

[Hemikiller]

The 30 circuit breaker for the auxiliary power feed wire mounts to the front stud of the starter solenoid. The wire is used for cars with power windows, convertible top, automatic seat back releases (part of the Convenience Group), rear defrost and power seat (Cougar only).

 

[jctodd66]

1973 Mach 1
no circuit breaker
Radio noise suppressor