I had a faulty reostat on my 81 sd 126 and did exactly as Barrie said I removed dash panel put in new bulbs and then removed old reostat and soldered in a lenght of auto type wireing from one pole to the other it's real clear when you take the old reostat out. I made the wire long enough that if I ever wanted to put in a remote reostat there would be enough wire ,but the full on light seems just perfect .Also removing the reostat dose not affect the reset on the trip odometer as the are the same nob....
William Rogers.....