Replacing rear signals

[Mongo40]

One of my signal lights is broken and taped together so I thought I would just put some new smaller ones on, I got the small diamond shaped LED ones you see for sale on Amazon and eBay but there is a problem, I'm not an electrical guy so it's probably something simple, when I plug them up the blinkers start blinking really fast and only four of the little LEDs light up, what am I missing here? I'm guessing I need some kind of inline resistor? Nothnin is ever simple!

[FJmonkey]

Yes, you will need a resistor to fool the electrical system and stop the fast flash. An LED is an open circuit just like a burnt bulb so the system is telling you a bulb is burnt. Not sure why only some light up. That might be a defect.