Usually if the relay goes the signal doesn't work at all.
True ^^^
You could use a digital volt meter and back probe the blinker bulb socket while the blinker is flashing and see what the blinker voltage reading is.
This is a VERY basic example of how the blinkers work:
Normally, the electricity will flow from the battery to the blinker stick then to the relay/flasher. The electricity then flows thru the wire....travels thru the bulb (lighting it up), continues flowing thru the wire then connects to the car, and then to the battery. There are alot more things involved, but this is the basics.
Electricity generates heat. The reason the blinker blinks is because the heat build up bends a piece of metal within the relay/flasher mechanism which in turn cuts off the supply of electricity (heat), once the metal piece cools off, it un bends and electricity again flows. The cycle repeats, and that is why the blinker blinks.
The left blinkers operate separately from the right blinkers. If only the right blinkers are blinking fast then obviously the problem is with THAT side of the car. A bad relay/flasher causes BOTH sides to be affected in the same manner. BUT if the left side is blinking fine then you will know that the relay/flasher is still good because it's still doing its job.
However much electricity is sent thru the wires is the same amount that needs to return to the battery.
Let's say for example you have a battery with one wire sending electricity to the bulb then from the bulb you have 5 wires sending electricity back to the battery. The light blinks as normal.
Now, let's say you cut one of those 5 wires leading back to the battery.......your four remaining wires have to do the job of five. Those four wires are passing the same amount of electricity as five, but they are sending it at a faster rate per wire in order to maintain the same total amount of electrical current.
So yeah, your blinker will blink, but it will blink faster due to the faster electricity (heat) flow.
I would look for a broken ground wire as being the problem. Sure someone will say a broken ground wire would cause the light to not flash at all. And they may be right on certain vehicles. But newer vehicles these days have electrical systems which share common 'negative' grounds, that one interruption could cause a problem. Anybody behind a car ever see the lights turn off when the driver pushes the brake pedal......poor ground......the electricity is looking for the easiest path back to the battery.....thru the brake lights