99 suburban,rear brake lights and turn signals work intermittently. Tail lights are fine on both sides. I have replaced bulbs and the circuit panel on the rear to no avail. I think it may be the turn signal switch itself. I also lose the cruise control whenever i hit a bump, like crossing a bridge, also. Could the ground be the cause of this? Another point of issue that may not be related directly is that my horn fuse blows whenever it is replaced and the driver side door jamb switch works intermittently as well. I hope someone can point me in the right direction as I am about to replace the turn signal switch.

Bad bulb, bad bulb socket, bad wire... get yourself a 12v test light and find out where there isn't power and fix the problem.

just check accurately bulbs if you mixed it could happen like that, some cars for the brake lights use two contact bulbs some of them single contact, two contact bulbs can give two signals which one is used for brake ligths and another for taillight, so check the bulbs carefully

ck fuse for rear taillights tis under the dash lower left of steering wheel. or if you still have the manual look in there under fuses.
also look for a bad ground but i doubt that.. if it's both rear out.
fast flashing well here's a chart with all sorts of info.
Problem What To Do Turn signals light, but do not flash Replace the flasher No turn signals light on either side Check the fuse. Replace if defective.
Check the flasher by substitution.
Check for open circuit, short circuit or poor ground. Both turn signals on one side don't work Check for bad bulbs.
Check for bad ground In both housings. One turn signal light on one side doesn't work Check and/or replace bulb.
Check for corrosion in socket. Clean contacts.
Check for poor ground at socket. Turn signal flashes too fast or too slow Check any bulb on the side flashing too fast. A heavy-duty bulb is probably installed In place of a regular bulb
Check the bulb flashing too slow. A standard bulb was probably installed in place of a heavy-duty bulb
Check for loose connections or corrosion at the bulb socket Indicator lights don't work in either direction Check If the turn signals are working
Check the dash indicator lights
Check the flasher by substitution One Indicator light doesn't light On systems with 1 dash indicator:
- See if the lights work on the same side. Often the filaments have been reversed In systems combining stoplights with taillights and turn signals
- Check the flasher by substitution On systems with 2 Indicators:
- Check the bulbs on the same side
- Check the indicator light bulb
- Check the flasher by substitution
hope this helps. may want to print for future reference. :)
hope this helps.

If you have no power getting to the circuit, it could be the turn signal switch. The brake circuit goes thru the turn signal.

There is no adjustment. The park lights are on a different circuit than the brake lights.
Do you have a third brake light that works. Its also on a different circuit but works from the same switch. Do your turn signals work. They use the same filament as the brake lights.
Also, the brake light circuit goes through the multi function (turn signal) switch.

Since the brake lights and turn signal lights use the same filament in the bulbs, the brake light circuit will pass through the turn signal switch. When a turn signal is used it cancels out the brake light for that side.

Let me know if your third brake light and turn signals work in the rear.
Also, if youy have not already, check/change the bulbs. The type of sockets those lights are in also get burned so look at them well.

The circuit board needs to be replaced. Which is the board that the bulbs sit in. If you remove the turn signal bulb. You will notice the bulb socket will be slightly burnt inside. I had the same problem with my 99 Denali and replaced the circuit board for $35.00. Now everything is fine.

CHECK TAIL LIGHT BULBS.IF BULBS CHECK OUT GOOD PROBLEM COULD BE CORRODED BULB SOCKETS OR BROKEN LOOSE WIRE IN CIRCUIT.

I was having the exact same problem as my brake switch was fine on my 95 suburban. However upon further inspection the problem was very simple i felt really dumb once i found this: the wire harness that comes away from the switch witch is a bundle of white wires that comes down and across the under side of the steering column had 2 damaged wires upon repairing this i have had no problems since then feel free to email me on this problem at [email protected] as i will do my best to help u out. But the problem is most likely a wire short out, or damaged wires for the normally open circuitfor your brake switch.

Bad earth connection.Clean or replce wire.

TURN SIGNALS WILL FEED BACK THROUGH THE TURN SIGNAL SWITCH.THEY ARE INDEPENDENT OUT SIDE ON THE CAR BUT NOT IN THE SIGNAL SWITCH.REPLACE THE SIGNAL SWITCH