Need help with 66 fleet side C20 taillights

[KilroyWasHere]

So my taillights recently stopped working and I have no idea why. My fuses and bulbs are good, and I'm still able to use my headlights are turn signals with no problem. I assume it's a possible ground issue, but I'm not sure. Any possible explanations?
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[oldies1938]

Check your brake light switch

[KilroyWasHere]

Originally Posted by oldies1938

Check your brake light switch

I'm still learning with these trucks, where is that located?
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[jtrichard]

First check ground

[sanford66]

Switch in under the dash by the brake pedal. Also I would ground the taillight housings to the frame. Joseph

[KilroyWasHere]

Originally Posted by sanford66

Switch in under the dash by the brake pedal. Also I would ground the taillight housings to the frame. Joseph

Ok I'll take a look at it in the morning. Thanks for the help!
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[oem4me]

Originally Posted by KilroyWasHere

My fuses and bulbs are good, and I'm still able to use my headlights are turn signals with no problem.
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Turn signals both front and rear are working? Brake lights? If NOTHING back there works, take a look at the connection point where the rear harness plugs into the main harness. It's about 3 feet short of the rear bumper on the driver side frame rail.

[KilroyWasHere]

Ok so I put in new bulbs and ran direct ground wires from the taillight harness to the frame. Here is what's happening:
Right side does not work at all
Left taillight is faint when applying brakes and turn signal
Left taillight is bright when lights are ON and applying turn signal
Everything in the front works fine, as well as everything in the cab. It's only the taillights giving me trouble. Should both wires be grounded on the left side? Or is there possibly a short somewhere?
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[Tazimafied]

I would double check the housings and clean the connections on the bulbs and in the sockets. Happened to me once in my '64 on the front markers. Everything was working fine, then one day, nothing. Water had got in to the housing and corroded the connectors and the metal grit made its way to the side of the socket grounding out the circuit.

[KilroyWasHere]

I'd like to thank everyone for the help. I replaced bulbs and fuses, and ran a direct ground wire connection from the battery to each taillight housing, now everything's working fine.
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