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Good day!

I’m seeking the forum’s help in deciphering a turn signal issue. In reading other similar posts, I suspect there is a ground or resistance issue, but I have a mixed bag of functionality so I’d like to ask for the view of this group of experts!

1. When head lights or parking lights are OFF, I have front turn signals on right and left. The left rear turn signal works, but not the right. Flashing ‘speed’ is faster than I would expect it to be, but is not as fast as if a bulb is out. Dash indicator lights both flash at the same time regardless of whither right or left indicator is selected. Dash indicator lights are very dim.

2. When head lights or just parking lights are ON, I have front turn signals, but NO rear turn signals on either side. Flashing ‘speed’ is slower than described in #1 above. Dash indicator lights function as described in #1 above. All other tail lights illuminate as expected.

I have checked all bulbs visually and functionally to make sure there are no broken filaments. I have cleaned sockets, contacts on wires and bulbs, the interface between the socket housing and the taillight opening and cleaned what I believe to be the ground connections for the rear lights. I have checked continuity and all circuits appear to be intact.

Your thoughts/opinions are appreciated.

Thanks much!

Mark

It does sound like a ground or an incorrectly wired bulb. Any added mods to the system you are aware of such as a connection for something like trailer lights or a third brake light or do any of the sockets look different and might be a newer replacement? Do the tail lights come on in both park and headlight position and at about the same brightness? Do the brake lights work and if so, is the brake light brightness on both sides about equal and much brighter than just the tail lights alone?

54ocmac;

The best I can do would be to explain what I found on my ’54 when the same sort of thing happened.

I had removed the instrument cluster just enough to replace all of the instrument bulbs, and while doing that the cluster fell a bit. At the time I didn’t notice, but one of the turn signal indicator wires had stopped the fall and the terminal became bent straighter than original. Again completely oblivious I reassembled, and the now straight terminal touched the reinforcement brace just behind the cluster providing an unexpected ground path. The result was craziness very much like what you described. By the way I put a couple of thicknesses of gorilla tape on the reinforcement bar . . . just in case.

HH56 advice of a potential ground is quite consistent with my experience. I would be on the look-out for unintentional grounds in the pilot circuits.

dp

Good day!

Thanks for your replies HH56 and DP!

There are no added options such as a third brake light or trailer towing pigtail. Taillights illuminate with parking and headlights. I’ll double check if the brake lights illuminate properly as I did not do that at this point. All tail lights are the same brightness. One thing that I noticed this morning is that when taillights are illuminated and turn signals on, there is a VERY faint flicker in-time with the front parking lights as they flash.

I’m going to, once again, go back through all the connections checking for undesirable grounds/shorts, poor contact, etc. Based on the number of times I’ve gone through everything trying to figure this out, it is something very subtle.

Thanks for you input and experiences! I’ll keep looking.

54ocmac

Checking grounds and connections one by one is the next step. The original thermal type turn signal flashers rely on having the correct resistance in the overall circuit -- mostly determined by bulbs and corrosion free connections and grounds -- to provide the proper conditions for the flasher to work. When the switch is placed in a turn position that completes a path to ground and the resistance thru the bulbs and wiring allows the heater in the flasher to start and work a bimetal strip. Too much or too little resistance causes the flashers to have a fast action or none at all.

Because of the way the entire circuit is constructed with the bulbs in parallel and a shared filament in the dual filament bulbs using what may be a poor ground, a high resistance at one socket will have the circuit seek another way to a better ground either thru an unrelated filament at another bulb on the same circuit or in the case of grounded indicator lights, thru what should be an isolated bulb.

I don't know if you have the simplified turn signal drawing that has been posted before but if not, here is an extraction showing only the turn signal circuit and how the flasher output power and brake light switch output goes thru the switch to reach the various bulbs. Note that the turn signal switch contacts can get dirty and are supported on fiber insulation sheet which can warp and move a contact out of position. A poor connection in the switch can also cause intermittent or strange operating conditions.

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  49-56 Turn Signal Extraction2.jpg (285.79 KB)

Hello again,

Thank you for your input and suggestions for resolving my dilemma! I have tried to put all of the info to good use. I’ve re-cleaned everything; made sure grounds are tight against clean/bare metal; rechecked continuity, etc. I replaced the circuit breakers on the instrument cluster. There are definitely improvements, but unfortunately, I’m still having one obvious issue. I still do NOT have a right rear turn signal.

The current improved situation is as follows:

1. With parking/head lights OFF, I have a properly functioning left turn signal front, rear and dash indicator light. Flashing is at a speed that I believe to be correct. Flasher is making an audible tic—-tic—-tic; not a rapid tictictic. The right front turn signal is flashing rapidly and there is no right rear turn signal at all. Flasher is emitting rapid, barely audible tictictic.

2. With parking/head lights ON, all tail lights function. The out-board left and right lights are slightly dimmer than the in-board. When left turn signal is initiated, the turn signal NOW functions as described in #1 above. Before, it did not function when parking/head lights were on. The right front turn signal flashes rapidly. There is NO right rear turn signal.

I took all of this one step further and checked the voltage coming through the line to the light bulb sockets. For the properly functioning left turn signal, at the rear connection, I’m getting a voltage reading that cycles between about 1.5Vdc and 3Vdc. It’s hard to be exact as it fluctuates constantly. I’m assuming this is due to the function of the flasher. For the right side, I’m only reading about 0.5Vdc with some fluctuation up to maybe 1Vdc. Voltage readings for the out-board/in-board tail lights is 4.8 and 5Vdc respectively. Ugh!

I’ve about resolved myself into having to use the old hand signals and or a right turn semaphore flag to signal my right turn intentions! Please advise your thoughts, if any, based on this updated status.

Thanks so much!

With tail lights only on are all 4 bulbs about the same brightness? If they are not fairly equal suspect some corrosion and a bad connection in a ground, wire terminal, or socket somewhere.

I don't see a mention of brake lights. With the headlight switch off so the tail lights are off, have someone push on the brakes so you can get a good look at the brake lights on both sides from a slight distance. As I recall, the brake/turnsigal bulbs are on the outside but confirm that by looking inside the trunk for the socket fed with two wires which is the brake and turnsignal bulb. The socket with a single wire is tail lights only. If you do have brake lights on both sides, are they they same brightness and much brighter than when only the tail lights are on? If no brake lights on both sides, that plus the turn signal issue would suspect a ground, bulb, or socket.

Are both sides using the same #1154 bulb for the brake and turnsignal bulb. The socket with a single wire for tail lights uses a #63 bulb. Also you might check the pins and sockets on the dual filament bulbs and make sure they are the same on both. I think the pins are offset with the dual filament bulbs but can't remember for sure. If the pins are offset is the same pin on the same side on both bulbs or near the same filament so both bulbs insert in the socket the same way. There were some inexpensive import bulbs several years back where the pins were a bit messed up. That coupled with worn sockets allowed the bulbs to slide in not keyed properly in the socket. Also, with worn sockets bulbs meant for another location or purpose with a different pin layout entirely could be inserted.

Poor contact in sockets and switch are known issues. For the socket, with the bulb out and looking directly inside the socket does the fiber plate with two contacts look flat and contacts appear to be at the same height. With the heavy spring pushing on the outer edges of the fiber plate from behind and the bulb pushing down in the center from the front condensed moisture can weaken the fiber plate and cause the plate to warp or kind of cup. This puts the contacts at a different level and often a contact does not make a good connection with the base of a bulb. Same with the switch if the fiber support plate there warps or corrosion in the switch is making a poor connection.

My take is that the contacts in your turn signal switch are dirty. You can take it apart and clean it or in a fit of pique you can just waggle the handle about a hundred times so that the contacts drag themselves clean. I have used both methods with success.

Hey Howard and Ross,

Again, thanks for the quick replies!

The out-board tail lights on right/left side of the car are the turn signal/brake lights. Both sockets have 1154 bulbs. The in-board lights on both sides are just running lights, but they have 1129 bulbs in them. Not sure why.

There is a difference between the 2 turn signal/brake light sockets. The properly functioning side has the 2 contacts passing through a round piece of unclad G10. I assume there is a single spring under that piece of G10. The non-functioning side has a different internal set-up. There are 2 springs (one for each contact). There is no G10 stiffener on top of those springs. The wire crimped into the contact passes through the spring and the contact rests on top of said spring. I would say that could contribute to the problem except for the fact that light bulb does illuminate,

Tomorrow I will double check the brake lights.

Now, for the switch mechanism, I’ve considered that could be a possible source. Although I have cycled it numerous times thinking there could be some corrosion/dirt, etc., nothing changes. I may remove it tomorrow, as well, so I can get a look at its’ condition.

I’m sure more to follow!

If you need to or decide to tear into the switch here are a few photos of the disassembled switch. These were taken by a poster from Canada who unfortunately passed a few years ago. I am sorry but I cannot recall his name or car at the moment to refer you to his project blog for more details on what is needed or anything to watch out for when taking the switch apart.

You can see the terminal positions as supported by the fiber piece on one view and the slide portion with the triangular contact plate that makes the connections on another. I colored in the terminals on the third and fourth photos to match wire colors and show how the mechanism moves the triangular contact plates to connect the various terminals. The wire colors were fairly consistent over the years and their full connections are shown on the simplified drawing of the turn signal circuit posted a few days ago.

If the fiber has warped and any of the terminals are depressed or otherwise out of position or if dirt or corrosion on any of the terminals has deposited, the switch will be intermittent or not work at all.

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  49-54 turn signal contact portion.jpg (57.77 KB)


  49-54 turn signal slide portion.jpg (62.95 KB)


  49-54 turn signal switch.jpg (66.35 KB)


  49-54 turn signal sw drawing.jpg (80.12 KB)