I have recently been converting the dash lights in my 1987 Toyota truck to LED for better illumination. The original bulb that lights up the heater controls was burnt out and I decided to start with that one. I removed the old bulb and placed the #74 type LED in the socket and now none of my dash lights work. I have tried putting the old bulb back in, testing the dimmer switch and been over the whole circuit with a multimeter and I am getting voltage and varying amps when I turn the dimmer. I don't see anything wrong with the circuit and was seeing if anyone out there did. This is the basic instrument cluster with no tach and the printed circuit board looks mint. Does having the stock bulbs instead of LED's in the gauge cluster make a difference that would result in this?

 

LED lights have polarity are yours correct ??