Dash lights. Led ?

fordnutjm · May 3, 2024

I'm still tracking some wiring Gremlins on the 73. I took the instrument panel out and 90% of the bulbs that was in there are LEDs. I tested them individually and it seems that they only work with the polarity in One direction unlike incandescent. If this is true, and I've replaced them with new LEDs, they would have to install with the positive side on the correct side of the opening in the back of the instrument panel correct? How do I know which circuit is the negative side and which is the positive side? I would like to replace with LEDs to have a brighter than stock instrument panel.

Steve McMahan · May 3, 2024

Look at this diagram, it shows + light voltage verses - ground for each bulb. Don’t forget, don’t replace the Alt. Bulb with an LED light, the system uses the incandescent bulb in that circuit as its indicator and the LED defeats the purposes of the warning function.

fordnutjm · May 4, 2024

Steve McMahan said:
Look at this diagram, it shows + light voltage verses - ground for each bulb. Don’t forget, don’t replace the Alt. Bulb with an LED light, the system uses the incandescent bulb in that circuit as its indicator and the LED defeats the purposes of the warning function.

View attachment 88344

Thank you! Exactly what I needed!

Don C · May 4, 2024

It's fairly easy to determine which side of the socket is the negative. The light (postive) trace pretty much runs around the outside of the circuit board, with the negative trace the second one in from the outside. You can see the layout in this post
https://7173mustangs.com/threads/71-73-mustang-printed-circuits-illustrations.43761/

351c1971 · May 4, 2024

I also left the turn signal incadescent bulbs in the dash cluster when I updated to dash LEDs. Was this necessary?

Stanglover · May 4, 2024

Dash LED's have been written about a zillion times. The one's I bought from www.HiPoParts.com , the Elite Series II, all had the pos side marked. I bought all my LED's from Bill with the exception of the headlight LED's
NOTE: installing LED turn signal bulbs require a grounded LED flasher on turn and hazard circuits. These are also polarity specific. On my car, I found the harness was wired incorrectly and had to make jumper wires to switch the polarity.

rhigg1959 · May 4, 2024

When I installed my HiPo bulbs, I still had issues with some of the bulbs not having good contact with the circuit board. I replaced
the circuit board and bulb sockets and had the same issue. I actually had to adjust the bulbs as I installed them. By this I mean I could not twist them
all in fully. Some I had to only twist in part of the way for them to work. They are all good to go. I am however, using the stock flashers with no issue.

Stanglover · May 4, 2024

rhigg1959 said:
When I installed my HiPo bulbs, I still had issues with some of the bulbs not having good contact with the circuit board. I replaced
the circuit board and bulb sockets and had the same issue. I actually had to adjust the bulbs as I installed them. By this I mean I could not twist them
all in fully. Some I had to only twist in part of the way for them to work. They are all good to go. I am however, using the stock flashers with no issue.

Rereading my comment, I realized I should have said LED turn signal lights, back and front, not just the LED's in the dash display.
I remember now I did have to do a little tweaking to get good grounds on the circuit board and clean the copper strip as well.

fordnutjm · May 5, 2024

Don C said:
It's fairly easy to determine which side of the socket is the negative. The light (postive) trace pretty much runs around the outside of the circuit board, with the negative trace the second one in from the outside. You can see the layout in this post
https://7173mustangs.com/threads/71-73-mustang-printed-circuits-illustrations.43761/

Ok I see what you mean. Thanks !

fordnutjm · May 15, 2024

When you pull the instrument panel most of the bulbs come out with the panel, one bulb that goes to the panel stays connected to a wiring harness, is this the alternator bulb? The brake bulb or?

rhigg1959 · May 15, 2024

Interesting. When I pulled my instrument panel, there was no additional wiring harness connected. Only thing I had to unplug was
the speedometer cable, the plug that goes into the circuit board and the tach cable.

fordnutjm · May 15, 2024

rhigg1959 said:
Interesting. When I pulled my instrument panel, there was no additional wiring harness connected. Only thing I had to unplug was
the speedometer cable, the plug that goes into the circuit board and the tach cable.

Yeah first I thought I lost one of the twist in sockets, so i bought another one. While checking the other lights (headlight & windshield wiper illumination etc) I noticed when I turn the key to run there is an unaccounted for light on a pigtail that lights up. Don't know where it goes ? It is close to the headlight switch.

fordnutjm · May 15, 2024

fordnutjm said:
Yeah first I thought I lost one of the twist in sockets, so i bought another one. While checking the other lights (headlight & windshield wiper illumination etc) I noticed when I turn the key to run there is an unaccounted for light on a pigtail that lights up. Don't know where it goes ? It is close to the headlight switch.

Actually, thinking about it I don't know how it would go anywhere in the instrument panel because every socket has a circuit going to it. The bulb in question looks to be original not something someone added, I just can't figure out what would light up with the key in the run position that isn't in the instrument panel?

rhigg1959 · May 15, 2024

The light switch and the cigarette lighter are illuminated. Could it be one of those?

Steve McMahan · May 15, 2024

That sounds like the headlight switch light. It plugs from the top of the adapter, that fits between the switch and the backside of the dash. I don’t have a pic that shows it, but I suspect someone does.

fordnutjm · May 15, 2024

Steve McMahan said:
That sounds like the headlight switch light. It plugs from the top of the adapter, that fits between the switch and the backside of the dash. I don’t have a pic that shows it, but I suspect someone does.

I have the light socket for this. The strange thing is the one in question comes in with the key in run position like the idiot lights do.

Stanglover · May 16, 2024

A picture speaks a thousand words.
That might help solve the problem.

midlife · May 16, 2024

1973 is unique in that the alternator indicator lamp is part of the main harness and plugs into the dash cluster.

fordnutjm · May 26, 2024

midlife said:
1973 is unique in that the alternator indicator lamp is part of the main harness and plugs into the dash cluster.

OK thank you !!!

GERMYS_72 · Dec 14, 2024

Stanglover said:
Dash LED's have been written about a zillion times. The one's I bought from www.HiPoParts.com , the Elite Series II, all had the pos side marked. I bought all my LED's from Bill with the exception of the headlight LED's
NOTE: installing LED turn signal bulbs require a grounded LED flasher on turn and hazard circuits. These are also polarity specific. On my car, I found the harness was wired incorrectly and had to make jumper wires to switch the polarity.

Geoff, I just swapped all the bulbs in my cluster to LED, except the two turn blinkers and the Warning Lamp / Brake warning switch combo socket, I left those 3 incandescent for now. How much trouble is it to install grounded LED flashers on the turn and hazard circuits ? Worth the trouble ?

Dash lights. Led ?

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