How to bench test fender mount turn signals?

Those fender mounted lamps are a PITA! I find they lose grounds or the bulb contact goes bad. I hit em with WD-40 every six months or so. I also find you may want to take the bulb out, put it on a little vise on the bench and tickle it with your soldering iron to build up the solder bulb on the end so it makes contact a bit better. Good luck.