saleen0101

Hello guys,
I need help regarding my interior lights. I recently changed all my exterior and interior light to LEDs. Nothing ricey or anything, just kept it stock looking , just different led bulbs instead of incandescent. Anyways, on my gauge cluster, when my lights are on, everything works fine , however, when I have the lights off during the day, my odometer and radio(stock) are dim like..and if I turn the lights back on they light all the way up.. Also (with the lights off), when I turn my right turn signal on, my radio and odometer flash with my turn signal. Any ideas?

when I put back all the incandescent bulbs back in my gauges, they work fine. I have no issues at all with turn signal or anything.

For my exterior turn signals, I switched out the turn signal relay for the leds since at first they would flash super fast due to the less current. So its the same as having tied in load resistors. I think I got it at autozone and it made my turn signals flash normal again.

I believe im not getting enough volts hitting my gauge cluster and that is causing my issue??
So its only when I put in the leds in that is making this happen.

cliffyk

The dash illumination system was not designed for LEDs, which have relatively low forward bias resistance and some reverse bias leakage, unlike incandescents which have much higher and non-polarised resistance characteristics.

Without getting too far into the wiring diagram I would suspect that there is some "cross talk" type partial reverse current flow that is causing both the dimmer odometer and radio lighting, and the interaction with the turn signal.

It could be that circuit modifications and/or one or more strategically placed blocking diodes could prevent this; study of the wiring diagram would reveal the possible pathways for such interactions and suggest where the systems might be isolated or blocked...

saleen0101

OK . So would you suggest resistors of some sort? I would hate to go back to incandescents, wish I could pin point what is really causing this issue. Thanks for the input .

cliffyk

What model year is your car?

[edit]

Never mind, it doesn't matter.

I suspect that it is something in the head unit's dual illumination scheme, which causes the display to be on when the radio is on and also dimmable, that is being loaded up in a manner is does not expect by the LEDs in the cluster.

They are both fed from the rheostat in the light switch and I suspect the LEDs are providing a current path to ground that is higher than the incandescent lamps would provide. This is draining the feed to the radio's display and dimming it.

Unfortunately the internal wiring for the radio is not shown in the shop manual diagrams. I would speculate however that a blocking diode in series with the radio's feed from the dimmer rheostat might block that reverse drain. That feed is supplied via a light brown/red wire in position 1 of connector C290a at the radio.



You can get the diode from Radio Shack, 3 for $1.69...

saleen0101

I have a 2001 mustang saleen.

saleen0101

Wow , thanks for the info. You seem very savvy in regards to electronics...something im unfortunately not in so much lol. So will this solve the dim odometer as well? Do you have any tips on installing this diode? Ill try to tackle this when i have the time, thanks again, hope this works.

cliffyk

I do not know. It is at best an educated guess, however I see no other point at which the lighting levels and interaction you have observed could be affected.

As to installing the diode, cut the wire 2"-3" back from the connector at the radio, strip the ends twist the diode leads and wire ends together (banded end of the diode toward the radio), solder the connections and tape it up.

Or, you could make it removable by using crimped bullet connectors (2 male and two female)



Use a decent crimping tool, not the crappy "squashing" things sold at Walmart:



Or better yet ($11.99 from Harbor Freight):