Turn signals did not work replaced parking light relay then they worked momentarily then rear tail lights went dim and turn signals stopped working again.

Bad flasher relay or blown fuse. Does hazards work if not and fuse is good than flasher relay is bad

did you cheked the fuses and relays?

You have a park lamp relay for all four corners. So if the front parking lights work, we will assume that relay is working.
The right rear and left rear each have a fuse powered by that relay. The fuses are in the box near the battery. If the fuses are hot, the problem may be in the wiring harness in the rear of the truck.
The license plate lamps are tied into each circuit, right and left.

The parking lights should be on a different circuit from turn signals - hazard lights. The bulbs usually have two filaments, one for each circuit.
On most models there is a tail light fuse and relay that handles front and rear parking lights.

TAIL LIGHT NOT WORKING

It can be faulty tail light bulb or its issue with tail light control switch or its wiring's are short.

Check the voltage at fuse slot of tail light.Do you receive 12 volt there.If not,then it says tail light switch is not receiving power supply.

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There are few help links related to your problem.I suggest you refer the list and check the help links.Click the link below:-----

Turn Signal Not working

http://technoanswers.blogspot.com/2012/11/turn-signal-not-working.html

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Right turn signal not working on Pontiac Car?

http://schematicsdiagram.blogspot.com/2011/12/right-turn-signal-not-working-on.html

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Only one side indicator light working on car?

http://schematicsdiagram.blogspot.com/2011/12/only-one-side-indicator-light-working.html

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Turn signals not working on 1987 Jeep Wagoneer?

http://schematicsdiagram.blogspot.com/2011/12/turn-signals-not-working-on-1987-jeep.html

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SOLVE YOUR 4 WAY FLASHER RELATED PROBLEMS HERE

http://repairhelpcenter.blogspot.com/2012/11/4-way-flasherturn-signal-flashersignal.html

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1994 Toyota Camry: Bypass Tail light Relay Circuit?

http://whatisbyme.blogspot.in/2012/04/1994-toyota-camry-bypass-tail-light.html

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2008 Toyota RAV4: Replace Tail light Lens Cover?

http://technoanswers.blogspot.in/2012/04/2008-toyota-rav4-replace-tail-light.html

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2003 Chevrolet S10 Tail light Fuse

http://schematicsdiagram.blogspot.com/2012/11/2003-chevrolet-s10-tail-light-fuse.html

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Chevrolet Parking light and Tail lamp light Wiring diagram

http://schematicsdiagram.blogspot.com/2012/11/chevrolet-parking-light-and-tail-lamp.html

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Car Tail Lights Not Working?

http://schematicsdiagram.blogspot.com/2011/12/car-tail-lights-not-working.html

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These details will help.

Thanks.

Then you need someone who can,like a repair shop

need more ifo

replace bulb make sure the front 1 works too will cause the indicator to blink fast,it is a bad bulb not relay when you replce bulb make sure you get the corect number most have 2 filament in bulb ,if you put a 1 filament bulb it will cause all kind of weird stuff like keeping your indicator on ,or your tail lights will be too bright on 1 side ,when you replace the dual filament bulb it as to be put on only one way ,if the wrong way it will cause the tail light to be bright and signal dim,the signal should be bight and tail lights dim,ive seen alot of people make that simple mistake including alot of mechanics,make sure you get the correct bulb number