Electrical question

[RandallMac]

Hello all,

 

I recently purchased a 1966 Skylark, so I am new to the breed. Historically I’ve been a Mopar guy so there’s a lot to the GM world I’m learning. 
 

my question is.... when I turn on the headlights the R rear tail light goes out and the blinker indicator in the car stays on solid (doesn’t blink). Additionally, and I believe they’re related, I think there’s a parasitic drain. Again, I’m guessing caused by the same culprit. Does anyone have any ideas as to where I should begin to look for the problem? Since everything works fine when the headlights are off, I don’t believe it’s an issue with the ground. Any assistance would be greatly appreciated. 
 

Randy 

[Bloo]

The signal circuit is the same as Mopar. Look for a bulb with a sagging filament that is touching another filament. Check all 4 corners. Make sure all brake/signal/tail/park lights have a good ground. Good luck. Let us know what you find out.

Edited May 28, 2020 by Bloo (see edit history)

[joe_padavano]

3 hours ago, RandallMac said:

Hello all,

 

I recently purchased a 1966 Skylark, so I am new to the breed. Historically I’ve been a Mopar guy so there’s a lot to the GM world I’m learning. 
 

my question is.... when I turn on the headlights the R rear tail light goes out and the blinker indicator in the car stays on solid (doesn’t blink). Additionally, and I believe they’re related, I think there’s a parasitic drain. Again, I’m guessing caused by the same culprit. Does anyone have any ideas as to where I should begin to look for the problem? Since everything works fine when the headlights are off, I don’t believe it’s an issue with the ground. Any assistance would be greatly appreciated. 
 

Randy 

 

The lighting problem is due to a bad ground at the socket, period. The 1157 bulbs used in the rear of your Buick have two filaments - the low wattage filament is for the tail light circuit and the high wattage filament is for the brake/turn circuits. These are tied together in the bulb at the ground side. If the ground is bad, the turn signal circuit grounds through the tail light circuit, so long as the lights are off. When you turn the lights on, there is now +12V on the tail light circuit and the turn signals can't ground that way, which is why the indicator stays on. The bad ground can be between the bulb and the socket, or between the socket and the housing, but the result is the same.   For some reason people have a really hard time grasping the concept of the shared ground in 1157 bulbs.

 

This is unrelated to your parasitic loss problem.

[Frank DuVal]

Ah, but wait, this is a 66. If factory wired, the front parking lights do not come on with the tail lights. The circuits are separated with the headlamp switch. 

 

 So first question is, did someone swap a wire on the headlamp switch to make the tail lights and parking lights on the same circuit? It is a commonly done procedure on Corvairs, same switch, same wires. Easy test is turn on headlamps, do the front parking lights light (one or both)along with the headlamps?

 

7 hours ago, RandallMac said:

I turn on the headlights the R rear tail light goes out

 

It was on with the switch off? It was on in the first (parking lamp) position? It was the turn signal or brake light on?  If the tail lamp filament was out, I would think the phrase would be "I turn the headlamps on and the right rear tail lamp does not come on". But you say it was on, then goes out. Why was it on?

 

I agree with Joe, 99% chance of bad light socket ground.

 

[joe_padavano]

4 minutes ago, Frank DuVal said:

Ah, but wait, this is a 66. If factory wired, the front parking lights do not come on with the tail lights. The circuits are separated with the headlamp switch.

 

 

That's irrelevant. He's asking about the tail lights, which do come on with the headlights.

 

[Frank DuVal]

No, not  irrelevant. He is discussing the blinker indicator in the car stays on solid!

 

8 hours ago, RandallMac said:

and the blinker indicator in the car stays on solid (doesn’t blink).

 

The blinker indicator is wired directly to the front turn signal bulbs. The path between the front and rear turn signals goes through the contacts of the turn signal switch.

[RandallMac]

It was “on” because the headlights were on due to ambient darkness.... same too goes for the tail lights. The attempted right turn signal was done upon entering a situation where I needed to make a right hand turn and I noticed the signal indicator in the car was solid and not flashing. I then switched it to the left signal which continued to blink as it should.. I got out of the car when I reached my destination and got out of the car, with the headlights on and tried the right signal, when I did, there was no flashing or tail light on the right. I turned off the headlights and the tail light and turn signal worked. I’m appreciative of the advise and as soon as I get home I’ll start looking at bulbs and grounds. 

[RandallMac]

And come to think of it... the two front marker lights don’t work at all.  (This is only day number 1 of me owning it) 

[RandallMac]

Ok gents, a follow up.. I checked the filament and ground, all of which I believe securely attached. One thing of note I did find... the right signal indicator blinks slower than the left, noticeably so and the bulb shines much dimmer than the left. I know I’m my newer vehicles the turn signals will flash faster or slower if a headlight is burned out. The right putter headlight is in fact burned out so is it possible that could be the culprit? I’m going to obviously replace it anyway, but the week or do it’ll take to be shipped will leave me wondering. 

[joe_padavano]

4 hours ago, Frank DuVal said:

No, not  irrelevant. He is discussing the blinker indicator in the car stays on solid!

 

 

The blinker indicator is wired directly to the front turn signal bulbs. The path between the front and rear turn signals goes through the contacts of the turn signal switch.

 

Again, irrelevant. Because the turn signal is what switches the rear lights from the brake light circuit to the turn signal circuit, the terminals for the front turn signal lamps are separate from those for the rear turn/brake lamps in the turn signal switch. This problem at the rear lamps is ONLY due to a bad ground at the rear socket, period. There is no other place in the car that the two circuits touch.

[Frank DuVal]

9 hours ago, RandallMac said:

It was “on” because the headlights were on due to ambient darkness.... same too goes for the tail lights. The attempted right turn signal was done upon entering a situation where I needed to make a right hand turn and I noticed the signal indicator in the car was solid and not flashing.

 

Ah Ha! Now, Joe is right! 👍  I read the original post as you turned on the headlamps and the turn  signal indicator lit up, as there was no mention of the turn signals being turned on anywhere in the post. If the indicator stays on when asking for signals, bad ground is 99% the problem. I won't go to 100% because I've seen things, as Farmers says.😄

 

If the indicator lamp lights with just the parking lamps on, it is a bad ground at the front lamp, and if the indicator lights with just the headlamps on, I've seen it with bad dash ground and also with bad dash light shields just illuminating the indicator with the dash lamps....  😯

 

Hence why no mention of turn signals being asked for......

 

5 hours ago, joe_padavano said:

Because the turn signal is what switches the rear lights from the brake light circuit to the turn signal circuit, the terminals for the front turn signal lamps are separate from those for the rear turn/brake lamps in the turn signal switch.

Yes, exactly what I said in my post.😉

[Bloo]

Frank: I read that the same way you did and could not imagine how it could even be, but like you... I've seen things.

 

RandallMac: I am not sure how your light sockets are built on that 66, but on some GM cars (and some others) they permanently crimp the socket base to the reflector and after decades it loses contact. You can have no ground when it looks fine. If that is the trouble, the best way to fix it forever is to solder a wire to the socket and run it to a good ground. I have also seen people who do not know how to solder successfully fix that problem by using a fuel line hose clamp to attach the ground wire to the socket.

[Ltc4748]

An easy way to see if there is a light socket that is not grounded is to connect a test light to the grounded battery terminal. Turn the lights on needed to make the feedback occur. Now touch the test light to the base of the bulb that quits working when you turn both the lights on, does it light the test light? A bad ground connection will make the test light glow steady or flash if the turn signal is flashing. The test light proves the bulb is not grounded by lighting the test light. Next touch the test light to the metal socket the bulb goes in, does it light there? If test light does not light on the metal socket the poor ground is between the bulb and the socket. If the test light does light on the metal socket then continue to check the ground path by touching the test light to what the socket mounts into and look for the results. You can determine exactly where the poor ground is this way so you can repair the issue. 

 

Also the same test light can be used to check for a parasitic draw/battery drain. On cars without any computers just unhook the ground cable from the battery terminal and connect the test light between the terminal and the cable. The test light will not light if there is NO battery drain. To see if your test light has a good connection and is connected correctly for this test open the car door or turn the key on and the test light should light showing there is a path for current to flow. If the test light does not light the test light is not working or has a poor connection.         For reference less than a .02 amp parasitic load on a new vehicle will not even make the bulb filament glow a dim red. Computerized cars are able to draw up to .02 amps and are fine unless they set for extremely long times such as months at a time. Then the battery will not start the car due to the discharged state If you want to use a test light on a car with a computer you must disconnect the cable , connect the test light between the Battery terminal and the cable, then with the test light connected it will probably be lit, while keeping the test light connected touch the cable end to the terminal the test light should go out, then take the cable away from the terminal keeping the test light connected. If the test light stays out the battery does not have a drain, if it glows dimly you must perform the test with an ammeter to verify it is under .02 amps or the manufacturers specifications.

 

Best of luck to you, Larry