First, please turn that "auto lamp" switch OFF. That blanked out my whole panel, LED or not. Next, it sounds like you're getting less than 12V at the panel, since the resistors drop the voltage to 1.5, which is all that's needed to fire the LED. With less than 12V at the panel, those LEDs may be getting 1.1 or so, and can barely fire. Since I onlt did the backlighting on my '98, the whole cost was about $35 for the cluster and temp panel, so it didn't pay to do it as DIY.
1998 SuperCab Lariat, K&N CAI, LED Halo headlights, LED gauge / temp / headlight switch panel mods