OT 55 Pontiac wiring question.

[casper50]

The light sockets that are in my speedo cluster for the left and right turn indicators are single wire bulb/sockets.  Looking at the wiring I'm thinking that they should be 2 wire sockets.  I do not see how by the diagram that each is separate from the other.  Looks to me that if the flasher sends the signal they will both flash.  Am I missing something and do I need to get 2 wire sockets?

[casper50]

no wiring gurus?

[kencombs]

Looks to have a common ground but power comes from different turn signal sw terminals

[casper50]

Is the flasher connection the ground?

[T120]

Not a wiring Guru,...but I found this 1957 Pontiac wiring diagram (all models) on the "Old Car Manual Project" web site.The diagram differs from the one you posted in that a 2 prong flasher unit is used and there is only a single wire as you mentioned going to each, ( LH or RH), dash signal lamp with ground provided directly by the lamp socket ...Maybe there was a change made along the way, (modification) perhaps to your wagon using a 3 prong flasher?

 

 

[T120]

Here's an enlargement of the area in question ☺️

 

[Dave72dt]

You should be able to check continuity of the socket with a bulb in place to see if the socket base is used as a ground and it does appear to use a 3 prong flasher.  I suspect a metal backed cluster which would become the immediate ground for those bulbs as well as other panel lights. I think you need to chase the ( x ) feed on  the flasher to see if it does indeed become the ground for the flasher.

[T120]

I believe you should find that X on the 3 prong socket should be connected to the power source, (positive in the case of a 1955 Pontiac), with ground provided through the turn signal lever unit...I've been wrong before. lol

[T120]

Just to clarify...Because on this forum with the older Chrysler vehicles , we are used to Positive battery as being ground and Negative as being the (hot) fused source of power... In this case a 1955 Pontiac...Positive battery is the (hot) fused source of power with Negative being ground....Regardless, X on a 3 prong flasher socket ,  (In this case it appears to be used in a 1955 Pontiac and should be wired to the  Positive fused source)... With a multi meter attached to "L " as shown on your diagram, the meter should show battery positive and then go to zero (negative) , (with the turn signal lever directed, either right or left doesn't matter) ,as the flasher unit used switches on and off...

Edited July 25, 2020 by T120
I added text to clarify

[50mech]

I believe your color diagram is in error and  the signals based on something else entirely.

Three wire flasher didn't come in until 59 and the signal wiring in your schematic most closely resembles a 61 tempest.

 

55 Pontiac shop manual includes no turn signals.

56 Pontiac shop manual separates the turn signal diagram while repeating the same diagram as 55 for the rest of the car.

I think you'll find the 56 signal diagram accurate.

 

 

 

 

 

 

Edited July 27, 2020 by 50mech

[casper50]

The one in my 55 manual has it in it.

 

https://youtu.be/E9WONw9s-HU

[50mech]

6 hours ago, casper50 said:

The one in my 55 manual has it in it.

 

https://youtu.be/E9WONw9s-HU

Well there you go. I'm not sure I understand. Were you not trusting the shop manuals diagram?

Edited July 27, 2020 by 50mech

[casper50]

The sockets in place now are one wire sockets.  I'm thinking that they are incorrect as the diagram shows two wire sockets.  How does the flasher make only the correct light blink when it's connected to both?  Is one a ground?

[50mech]

Oh okay....I couldn't see it in the video before....your 55 manual does show 3 wire flasher unit......

Edited July 27, 2020 by 50mech

[T120]

Mike, Thank you for posting the "you tube" video of your 1955 Pontiac shop manual showing the wiring diagram...When you mentioned the speedometer cluster in your wagon only had one wire going to each dash lamp signal socket I thought the same as, 50mech, that the coloured wiring diagram you posted had it wrong and a 2 prong flasher unit should have been used - as in the  the 56 wiring diagram, 50mech, posted...much easier to follow. Sorry, that doesn't answer your question...I would rewire as per your shop manual.?

[casper50]

The shop manual is the same as the colored diagram.  I'm not understanding the diagrams.  Where's the ground?  Is the flasher or the column wire the ground?  How does it flash only on the correct light if the flasher is hooked to both?

[50mech]

Here we go.

[T120]

Deleted...

Edited July 27, 2020 by T120
Delete

[casper50]

I have the diagram.  I just don't understand it.  Thanks anyway.

[50mech]

I can't make sense of it either. Even with a two wire socket it would still do the same thing. P and L are powered at the same time on a typical 3 prong flasher. Even if they weren't, two wire or one. This would make it alternate between both indicators lit and just the side being used.

Even if the sockets were isolated.

The way it's wired to P is gonna light both at some point in all scenarios I can think of.

 

A dual filament bulb with a two wire socket and chassis ground is all that makes sense, then both would light but the one being used would blink brightly.

Thing is, 55 and 56 call for the same bulb.

 

I'd probably use just x and l and let the single wire sockets work as in the 56.

Edited July 27, 2020 by 50mech

[kencombs]

My reading of the original colored diagram is that the side that is common to both sockets is ground.  Power comes from the single  wire.  Tracing the path back to the fuse seems to confirm that.  Fuse/flasher/switch then out to one or the other indicator's hot side.   second connection shown is only from one socket to the  other, nothing else connects to it.  So, my reading is that  'wire' is really the instrument panel metal.

 

That is, if the single wire socket has the shell grounded.

 

I thought I posted this a couple of days ago, but must not have hit submit.

[T120]

I agree, in that I fail to see where a wire connected back to P on the flasher unit is required.The1956 diagram with ground provided by the lamp sockets makes more sense, the common connection as shown on the 1955 diagram rather than connected to P  should show as being chassis ground, with only X and L ,as mentioned, connections required at the flasher unit..

Edited July 27, 2020 by T120

[casper50]

Glad that I'm not the only one that couldn't make sense of this.  I'm going to run a single bulb socket and wire it up on a bench and see what happens.

[T120]

Okay, Looking at the 1955 diagram again, I can see possibly how it would work....With the right or left front turn signal lamps (fitted with the proper bulbs) wired in parallel with the right and left indicator lamps as shown on the diagram and with an additional ground switched through the P contact internally as provided by the stock 1955  turn signal switch and flasher unit, this may work.This would provide a redundant ground as switched through the stock turn signal switch for the indicator lamps.  I don't have the parts at hand to check my theory....

Either way as with previous suggestions, I believe both ideas would work.

[50mech]

2 hours ago, T120 said:

Okay, Looking at the 1955 diagram again, I can see possibly how it would work....With the right or left front turn signal lamps (fitted with the proper bulbs) wired in parallel with the right and left indicator lamps as shown on the diagram and with an additional ground switched through the P contact internally as provided by the stock 1955  turn signal switch and flasher unit, this may work.This would provide a redundant ground as switched through the stock turn signal switch for the indicator lamps.  I don't have the parts at hand to check my theory....

Either way as with previous suggestions, I believe both ideas would work.

As far as I know P is only capable of providing 12+ or it's open.