I've seen both. The simplest answer is to change it. If you're into electrical you could try to get a wiring diagram and check it, but automotive wiring diagrams don't always say what wires do, often just where they go. There's a pretty good chance it's the resistor, or the plug. Usually it's best to buy the kit with a pigtail, and change both if there's any signs of heat, melting etc.
Mine works on everything but high, same problem?
I've seen both. The simplest answer is to change it. If you're into electrical you could try to get a wiring diagram and check it, but automotive wiring diagrams don't always say what wires do, often just where they go.
There's a pretty good chance it's the resistor, or the plug. Usually it's best to buy the kit with a pigtail, and change both if there's any signs of heat, melting etc.