# help troubleshooting out brake/directional



## 70conv (Jun 25, 2012)

Guys,

My drivers side directional and brake light are out on my 70 conv. I've pulled the lens and bulbs and there is no power to the socket on the second contact when there should be. the Tail light works fine. Can someone offer some advice as to where the problem might lie? Does the harness to the rear of the car run on the drivers or passenger's side???

Thanks,
Mike


----------



## PontiacJim (Dec 29, 2012)

70conv said:


> Guys,
> 
> My drivers side directional and brake light are out on my 70 conv. I've pulled the lens and bulbs and there is no power to the socket on the second contact when there should be. the Tail light works fine. Can someone offer some advice as to where the problem might lie? Does the harness to the rear of the car run on the drivers or passenger's side???
> 
> ...


Mike,

Miracle of miracles. I just happened to have a wiring harness diagram that may help. Not an expert on wiring and maybe someone else can add to this.

I assume the front turn signal operate on that side? Then it may be in the rear harness as you have asked about.

The wire harness typically travels under the carpet, and I believe under the drivers side. But look at the diagram. You want to isolate your problem and narrow it down. I would first locate the plug "left rear body connector" found in the diagram. Unplug it here and locate the wire that powers the brake/turn lamp. 

IF you have an Ohm meter available (not needed, but can be a helpful test at this time -just skip this section and proceed), you can test for a short or wire that is grounding out. If you touch the 2 contact probes of the Ohm meter together, the meter will jump to show continuity between the two contacts. Now if you touch one probe to the body (good ground) and touch the other probe to the tail light socket contact that is not working, you should get no movement of the Ohm needle. If it jumps up real high, as you did when you connected the 2 probes by themselves, then you have a wire ground out on the body. If the needle doesn't move, good sign. 

Next apply 12 volt power to the connector to the wire that supplys power to the bad brake/turn signal light (light bulb in place), you can use a battery charger and length of wire. Clip your ground to the car and touch the exposed wire end to the contact in the connector going to the rear light. Don't short anything out, be careful. If the light come on, then you know that that section of wire harness is good. If it does not come on, then you still may have a break in the wire harness (which could be grounding out), bad ground, or, most likely, a bulb socket that may be corroded and gone bad. They make replacement sockets w/wire, so it may be this which is a known sore spot for tail lights.

If the light does work, then you have to move into the wire harness that goes from the connector end you just unplugged to the "main body connector" -unplug it here at the "main body connector." Again, if you have an OHM meter, do the test to see if you may have a dead short in this section of the wiring harness. If this is good, I would use my battery charger/wire and put power to the same wire that powers the brake/turn signal light. This will send 12 volts down the wire harness to the other end (main body connector). Now you need a 12 volt test light/probe. Clip your test light clip to a good ground, then insert the pointed probe into the wire that should have 12 volts coming through it from your battery charger end. The test light should light up if you don't have a broken wire or short. If it does not light up, then your problem is in that section of wiring harness.

The next section of wiring harness now goes from the "main body connector" to the "bulkhead connector" on your firewall. This is now getting into some deeper work/dis-assembly that will become a little more involved. I won't proceed any further as I am hoping it is either in the rear at the tail lights itself or somewhere in the harness that will be easy to detect and/or repair.

Keep us posted and let us know what turns up, and we can try to go from there to help you out if we can.:yesnod:


----------



## 70conv (Jun 25, 2012)

Thanks Jim. Can you tell me something about the 70 taillight arrangement? On the right side, that I assumed is working ok, I noticed that when I put on the blinker only the left sided (inner) lamp goes on and when I step on the brake the same lamp goes on. That means when the directional is on only the inner lamp blinks without any indication that the brake pedal is being depressed on the right side. Is this the typical arrangement for all 70 GTOs?

Mike


----------



## PontiacJim (Dec 29, 2012)

70conv said:


> Thanks Jim. Can you tell me something about the 70 taillight arrangement? On the right side, that I assumed is working ok, I noticed that when I put on the blinker only the left sided (inner) lamp goes on and when I step on the brake the same lamp goes on. That means when the directional is on only the inner lamp blinks without any indication that the brake pedal is being depressed on the right side. Is this the typical arrangement for all 70 GTOs?
> 
> Mike


Mike,

Most older cars have a dual element bulb known as an "1157," which has 2 contacts on the base of the bulb. The single element bulb is the "1156," which has 1 contact on the base of the bulb and is generally used for something like your back-up lights. Make sure you have the correct bulbs as I have been given the wrong bulbs at the parts store by those with no experience with older vehicles and then read the computer/part wrong.

The "1157" bulb uses one element when you turn on your parking lights. It generally has a lower intensity. The other element burns brighter and is for your turn signal/brake light.

If you activate the turn signal by itself, the light flashes. If you activate the brake by itself, the light remains on during your braking action. Now when you have your turn signal flashing and you hit your brake, or if you hit your brake and then activate your turn signal, it is the turn signal that seemingly over rides the brake light even though they are both actually on. If the brake light over rode the signal light, then you would not be able to signal as you were slowing down or coming to a stop, or stopped at a light. I am no expert, but it makes sense to me that the flasher unit interrupts the power being sent by the brake light switch in order to make the bulb element flash on and off - but I am guessing here. Do you know that your flasher unit is good? They also go bad. 

If you look at the wiring diagram, you will see that the outside lights are connected and both should come on together. The inside light is your back-up light. The diagram shows the wire for the turn/brake (Stop & Dir LP Feed) element in the "1157" bulb, and the wire for the parking lights (Tail LP Feed). You also see the ground wire connection, but I think this is done off the side of the bulb socket, so you will only see 2 contacts when you look into the bulb socket.

I know this is not original, but I suggest adding a third brake light in the back window like the newer vehicles have. You can get a nice slim design that will be rather hidden, but be effective. Placing down on the package tray in the rear window makes it very visible and at a good height for those drivers that are behind you drooling at your car and not paying attention as they try to figure out what kind of neat old car that is - just extra insurance in my opinion. I run a third light in my Lemans and could see the reflection of it in my back glass when I hit the brakes, especially at night. When I popped a fuse (I too had some electrical problems & knew it was the light bulb sockets as they were somewhat corroded), I knew about it because I would not see the reflection from the extra light. I could then quickly put in another fuse before someone rear ended me while they were texting or talking on the phone. I honestly don't know how to hook an extra brake light off of your existing brake/turn signal light at the rear harness as I simply added a wire coming right off my brake light switch all the way back to the third light, so there was no interference with the turn signal use.


----------



## 70conv (Jun 25, 2012)

Thanks so much Jim for taking the time to help me with this. So judging from what you said and the wiring diagram, BOTH the bulbs should light when either the brake or directional is on, with the directional interrupting the brake so you can signal even when pressing on the brake.

When I took off both lenses here is what I found: with the lights on only the low intensity filament is lit on the right, but on the left both the low intensity and high intensity filament is lit with only the lights on. When I step on the brake or put on the directional, only the inner bulb on the right has the high intensity filament lit; the outer on the right doesnt light and on the left both are already lit with just the lights on so the brake/directional has no effect. I'm beginning to think the whole harness is screwy. Getting the right outer filament working shouldn't be that tough, but I'm at a loss to explain why both filaments are lit on the left side??? 

Again any help is greatly appreciated. 
Mike


----------



## PontiacJim (Dec 29, 2012)

Mike,

Sounds like you definitely have a real light problem going on. You can fix it, but it may take a wire-by-wire trace. Has anyone ever cut/spliced the wires? Sounds almost like that may have been done and someone crossed them over. The socket which you described as having the park lamp element on and the brighter brake/turn element on at the same time when you only have the park lights on can be tested. While it is doing this, pull the bulb and use your light tester to see if you are getting power from the park wire contact, which you should, AND from the brake/turn wire contact. If you only have power at the park light contact and not at the brake/turn wire contact, then you may have a bad light socket. Just for fun, pull the bulb and put in a different one. Could be a defective bulb on the inside. At this point, I would also make sure that every bulb is new just to eliminate any bad/defective bulbs.

Don't get overwhelmed by it. Break it down into smaller components in your diagnosis. Treat each system separate - park lights, brake light, turn signals. Remember that to do this, include your front lights; park & turn signals. You could very easily have a problem up front that is causing your woes at the rear, so you want to eliminate this as well. Try taking the bulbs out of the front lights, install the ones in the rear, and see if there might be a change.

You want to isolate each system. Electrical problems are the worst and can be frustrating and time consuming. You definitely need a test light and an Ohm meter (easy to get a cheap one at Home Depot, Lowes, Radio Shack, maybe Walmart or autoparts stores). You can test each wire in the system with the Ohm meter by touching one probe at one end of the wire and the other probe at the other matching end. Now obviously the Ohm meter test leads only go so far, so I rig up another longer test wire having an alligator clip on both ends. You can get a small nail or something to stick in the electric connection/plug, clip the alligator clip to it, then clip your other alligator clip to the probe end on your Ohm meter. Make sure the alligator clips/probe don't touch any metal and ground out -wrap one up with electrical tape where the probe/clip go together, or maybe place a piece of cardboard under it, or something, to insulate it from grounding out. With the other probe from the Ohm meter you can now touch/test the corresponding color coded wire to see if the Ohm meter responds. If it does, then the wire is good and conducting as it should. If the Ohm meter does not jump up/move, then you have a break or its grounding out somewhere (could get pinched) -or even cut and spliced to the wrong wire if anyone messed with the original wiring harness. But typically a wire that is grounding out will pop your fuse, and you have not had that happen, so I don't think you have a hot/power wire grounding out. Got to do this with each wire that goes back to your tail lights. Time consuming. So you have to do this with each light socket to the left/right body connector, and then from the left/right body connector to the main connector. Pull these all apart at the connectors first before you begin your testing -you have to isolate each harness and then test each wire.

The 2 small contacts inside each light bulb socket are spring loaded. You will see the flat head formed by the contact in the socket that your bulb contacts press up against to supply them with power and light 'em up. Behind the contact head in the socket is a small spring -much like the small spring in an ink pen. This keeps pressure on the socket contacts and your bulb. You should be able to press the socket contact in and it should spring right back out. After time, corrosion gets in the and they no longer have that springing action. You need that, and it can be a sign that the corrosion may be causing you your problem.

I just checked, YouTube has several video's on "Checking Car Wiring Circuits For Continuity with a Multimeter." This will give you an idea of what to do. There are other tutorial videos as well. Should help you out.:thumbsup:


----------



## Mike E (Jun 9, 2018)

Help. I took off the rear taillight cover, but can't get the bulb out. Any ideas or thoughts?


----------



## PontiacJim (Dec 29, 2012)

Mike E said:


> Help. I took off the rear taillight cover, but can't get the bulb out. Any ideas or thoughts?


I usually break the bulb, then with a pair if needle nose pliers, grab a side of the bulb base and rotate it to collapse the base inward. You are basically destroying the base by collapsing it inward. Move the needle nose pliers to another side if needed and repeat until you can rip that base out. By rolling the base inward to collapse, you should not damage the socket. :thumbsup:


----------



## Mike E (Jun 9, 2018)

Thanks PontiacJim, I tried your method and it worked. Man, what a pain in the @ss that was, lol. Well, onto my next repair. Cheers! ?


----------



## PontiacJim (Dec 29, 2012)

Mike E said:


> Thanks PontiacJim, I tried your method and it worked. Man, what a pain in the @ss that was, lol. Well, onto my next repair. Cheers! ?



Good deal! :thumbsup: That is the best way I have found to do it without damaging the socket. You may wind up shredding the brass base and pulling it out in pieces, but it works.


----------

