2000 Pontiac Montana Has Short In Turn Signal.

You may try putting dielectric grease on all of the bulb sockets after you clean the sockets with a good quality electronic cleaner. and I would also clean and put dielectric grease in the sockets. I would suggest this since replacing the bulbs seemed to help with the problem. Good Luck electrical problems are usually the most hair pulling problems there are.

Check to make sure a leak hasn't developed around the bottom of the windshield, sometimes there are weep holes there that can get clogged resulting in water trickling down the inside of the firewall. If water reaches fuse box, wiring, etc., it can wreak havoc.

Also check all of your ground connections. They are often behind intermittent electrical problems.

Noticed last night that the taillights came back on after I bumped one of the rear taillights but still had the same symptoms with turn signal and brakes.

Sounds like you have more than one problem going on. Before you spend the $400, I'd take a few hours and trace out the wiring, check grounds, clean connections, bulb sockets, etc. For good measure, I'd change out the flashers too, they're cheap.

I think kramarat got it in #2 - bad common ground connection on one side. With just side/tail lights on, appears normal as the tail bulb with no ground completes a ground circuit via the brake bulb, then the brake bulb on the other side, then ground. The brake bulbs have lower resistance than tail, so tail is nearly as bright as normal and the brake bulbs don't light up.

When you brake the above doesn't happen so the tail light on the bad side goes out. Similarly, odd things happen when you put turn on. So what appears to be a bunch of different problems is cured by fixing the ground. For Christ's sake do that before paying $400!

If you do a sketch of the wiring system you'll see what I mean.

Cheers.........Codey

So, you guys are good, thank you very much. I found that in both of the two rear taillights that the ground wire at the connection to the assembly had at some point really overheated and made a bad connection. After cleaning both of them I currently see no further symptoms of the headache I was having before. Now I am just left wondering what caused it in the first place. Any ideas?

More than likely was caused by corrosion caused by atmospheric factors and possibly a metal composition that corrode at a rate that is somewhat accelerated by the humidity and that is one reason for the use of good dielectric grease that will help in eliminating the corrosion. On vehicles that I have done extensive wiring on I prep all of the connections with it even if it is just a body to frame ground strap

you may need to clean the contacts in your 4 way hazard switch or maybe the circuit board in the tail light housing is bad. i have had to replace the circuit board in my GM pickup truck

Thanks you guys. In any case I think I have saved the $400 and I appreciate the help. If there are any other thoughts on preventing further corrosion it would be appreciated. Thanks again.

It's an earth fault, check the ground terminal to the light panels, I don't know if you have printed circuit boards to your light clusters but it's a good idea to unplug these a couple of times to clean up the contact, also check the green/yellow from the panel to the chassis frame. Hope this works.

Bazzer.

I read your post & the first thing I thought before reading down the replies was a bad earth conection for the tail lights if ever a fault happens that a diffrent light operates to the 1 that is suposed to operate gernerally I have found bad earths every time or some 1 putting in the incorect bulb meaning a single filament instead of a dulal element bulb & yes they are tight but I have had so many people force them in you wouldn't believe me

in Australia the early holdens regularly had this problem because of 1 earth point under a screw for all the tail lights & when this was disconected or corroded this meant when the brakes were operated the brake lights could only get the parth to earth through the comon earth conection & back to the indicators & park light circuit up to the front of the car & through the front lights & to earth they will all glow even though it will be at about 1/3 of normal brightness of the bulb

the earth return on the rear lamp cluster has failed, connect multi meter to earth lead on lamp cluster and other lead to chassis and i think you will find its open circuit