Originally Posted by eb4tx
I'm confused about the license plate bulb that is required for my 1978 Safari. The original holder is the chrome Yankee 331/332 model. The socket is a dual contact type. Yet when I look in my original owners manual, it calls for a #89 bulb, which is a single contact bulb. I removed the holder and it does have two wires running to the holder. I'm assuming the ground is acchived when you mount the holder to the trailer. Why would a license holder require a dual contact bulb?
I have never seen a double contact in that light which is made by Truck-lite. My guess would be that it has to do with a grounding issue. Airstream may have need to do it that way to make sure it worked every time and all the time. Are the two barbs on the side the same distance to the bottom or are they off-set? In other words is it like an 1157 style or an 1142 style socket?
It may be that you can change the whole fixture so you can replace the bulbs (as needed) with something that is easy to find.