98 s-10 blinkers and brake light work but when i turn on the headlights the right side brake light dont wrk and the blinker goes fast

Your right rear turn signal bulb is blown.Replace the bulb and the fast blinking will stop.

mporteous, It sounds like you have a light switch problem. I can't think of any other reason for the running lights and tail lights not working in this situation. Are your brake lights working when the headlights are off and how about when they are on? Do your four ways hazard lights work in these situations? Try all the lights under these conditions. The reason the left turn signal blinks very fast is because one of the bulbs are burned out. Try the left signal and one light (front or back) will stay on and the other will not come on at all. Replace the bulb that does nothing. Do this before you try all the lights in different situations. I think that you will have to replace the light switch. Good luck with this.

Usually a fast flashing signal is because one of the bulbs is burned out or shorted out. If the signal and brakes use the same light which many cars do then check the wiring to it and replace bulb. If burns out again then it has a short between the signal switch and the actual light or the brake wiring to it is shorted.

you have a short in the wireing fix it fast before you have a "fire"

make sure our lights at rear are grounded sounds like a bad earth

most likely a bad ground in your electrical system; consult your local mechanic

Generally means that a bulb is out.
When a bulb blows, then the blinker has less electrical resistance, so the blinker works at a faster pace.
Have someone in the car as you inspect all lights.
.... and! As long as you have an assistant, check the headlights, stop lights, license plate light, brake lights, emergency flashers ....

when you use the right turn signal, does it blink faster?. Could it be the bulb holder is damaged or rusty?

Using a test light check to see if there is power to the wire at the plug where the bulb is for the blinker. if so the socket is bad. if not check to see if the light assembly is working for ex. the parking lights or the brake light ect If those lights dont work then check the fuse for the right rear tail light. Hope this helps.

Usually a fast turn signal means that there is a light out. You should probably check all of your lights, including back-up lights, and turn signals. If there is one out then replacing the burnt out bulb should fix the problem.