Black Top Racing (Page 2/2) OldGuyinaGT DEC 15, 11:36 PM The LEDs I used are simple replacements for 194 bulbs. They have some characteristics that are vastly different from incandescent bulbs but they are not some special assembly. There are additional components on these LEDs but no "chipset", per se. There are four diodes and a pair of resistors (and actually three LEDs). The resistors limit the maximum current through the LEDs; the diodes form a bridge circuit to allow the LEDs to light regardless of which way the assembly is plugged in. The dimmer worked equally well when I tried other LEDs that just had limiting resistors, but they just weren't bright enough (and they were polarity sensitive). The LEDs can dim because the transistor in the dimmer circuit acts as a variable current limiter to control the current through this circuit (includes all the illumination lamps/LEDs). This is a common emitter transistor circuit and the potentiometer in the thumbwheel control adjusts the drive to the transistor (the current to the base terminal). This variation in the current limiting of the dimmer circuit is not linear; fortunately the perceived brightness of an LED as current is varied is not linear either, so the adjustment of the brightness of the dash looks pretty smooth as the thumbwheel is turned. The thumbwheel pot has to be in good condition; I replaced mine because it was rough and presumably dirty and the dimmer worked but was uneven. The new thumbwheel fixed all that. Some 12v LEDs are made with enough individual LEDs in series that they do not require resistors to limit the maximum current through them; those might not respond to this dimmer circuit very well (I have not seen any 194 replacements that do not have resistors though). theogre DEC 16, 02:59 PM Careful because Often SMD LED are not 1 LED per "chip package" like most "old" standard LED in 3 or 5mm (T1 or T1¾ ) case. Red single LED drops ~ 2v (1.9 to 2.2 depending on exact formula etc.) Link resistor is 47R0 mean 47 Ω R can move to = decimal point. IOW 4R70 is 4.7 Ω Again Many "Fiero Dimmers" have problem most covered in the cave. Have any issues w/ normal 194 then most only get worse w/ LEDs to replace them. "Best" way to dim LED in Fiero is use one of the small "Arduino" MCU and maybe some MOSFETs to replace the OE Transistor. This can allow any OE knob to use the full range then output to PCM to the LED. Or if you mix LED and Normal Bulbs can use different PCM output to each type so both will dim close to same. Can I make one? Yes. Will I? No. Even then LED say 12v but Cars run at 14-15v w/ engine running. That alone can shorten the life. Worse Car Power is Very Dirty and why many things have Surge Protection etc. but you never see Replacement LED have this that quickly fries them. Normal bulbs don't care unless maybe Alt is bad and outputs 18v or more but then you fried ECM Radio etc. before the bulbs burnout.