[Parkman51]

Today I checked on a few electrical things - and after far too long, realized that the trunk light wasn't broken, but instead, it only goes on when the parking lights are on. In retrospect, this makes a good bit of sense (you don't need a trunk light unless it's dark enough for the parking lights to be on) but I felt rather foolish when I figured it out. The electrical diagrams in the shop manual were quite helpful.

Today's additional question:
What could have gone wrong with the electric clock? I did a continuity test across the fuse on the back of the clock, and the meter beeped, so it's probably not a bad fuse, but the clock doesn't seem to function.

[Bill Hanlon]

I'm not sure of the clock in your '55 Pontiac, but I many clocks of this era were mechanical clocks that were "wound" every few minutes or so by an electric motor. As the clock wound down an arm with a contact on the end would make a quarter turn or so, finally touching another contact which would activate the "winding motor" for a second or two. The motor would wind the clock spring, starting the process over again.

Assuming you have battery voltage at the wire going into the clock and the clock is properly grounded, I'll bet the contacts are dirty. Try this youtube video. The guy is really boring, but the video will give you a good idea of how your clock works. You can even manually wind it to verify that the clock will run okay once the winding mechanism is fixed. https://www.youtube.com/watch?v=VyHFaNxmn3g

[Parkman51]

Great lead on the clock, Bill.

Today I got the carburetor back, and installed it right where it belongs, after scraping off the remains of the old gasket. It's been very nicely rebuilt - the guy who worked on it said the bowl was full of varnished gas and the jets were completely clogged.



However, one problem slain and another arises: when I tried to start the car after reinstalling the carburetor, nothing happened. Not even a click from the starter solenoid. Also and possibly related, there seems to be a short in the Fuse 9 wiring (stop lights, dome light, courtesy lights). Fuse 9 was blown when I checked the fuse panel, and when I tried to swap in a new fuse, it blew as soon as it touched the contacts.

Nothing's changed with the car's wiring since I removed the carburetor, the only things I've done were to install the taillights and figure out the trunk light.

So today's one question:
1) What could be going on with the electrics? What tests should I run, and how can I fix it?

[Bill Hanlon]

Define "nothing happens". Do the headlights dim when you turn the key to the start position?

[Parkman51]

The headlight's don't dim at all that I can see, Bill. Nor do the dash lights, when they're on. The parking brake light does go out completely, though.

[Bill Hanlon]

Does the ammeter deflect at all when the key is moved from off to run? Run to start?

Is the transmission in Neutral?

[Parkman51]

Bill, you're a genius. I must've bumped the shift lever at some point and it knocked over into Drive. I put it back where it belongs and it started on the fourth crank - as soon as the carb filled with gas.

Now I can get back to the clock, and wondering about the courtesy light fuse.

[Bill Hanlon]

Originally Posted by Parkman51

Bill, you're a genius.

Tell my wife.

[Parkman51]

To Bill's wife: he's a genius.

Today I got the electric wiper motor in and mounted it in the correct location. It fits nicely, but I haven't done any of the wiring yet.



I also tried replacing the courtesy light fuse with a new one (thought maybe the old ones were just bad) but the new fuse burnt out again immediately.

Today's two questions, therefore...
1) I'd like to keep the original wiper switch, if possible, especially since the switch that came with the motor doesn't have the button to activate the windshield washer (which I assume works off the vacuum system somehow). Any ideas on how to modify the vacuum wiper switch to work with the electric motor?
2) On the courtesy lights: The more I look at the wiring diagram (12-0 in the shop manual) the more confused I get. The circuits on fuses 3 (tail lights) and 9 (courtesy/dome/stop lamps) seem to meet somewhere, which perhaps explains why the trunk light only goes on if the parking lights are on. Otherwise I have no idea why the trunk light works at all, since it seems to be on fuse 9, and nothing else on fuse 9 works. Where should I start?

[Bill Hanlon]

I looked at the wiring diagram and do not see "circuits on fuses 3 (tail lights) and 9 (courtesy/dome/stop lamps) seem to meet somewhere". But I did notice that the turn signal switch is not seen in the wiring diagram.

Question for Larry: Were turn signals optional in '55 Pontiacs?

I've followed the wiring diagram circuits for fuse 3 (red) and fuse 9 (green), but cannot find anywhere they meet'

The missing turn signal switch would need to be inserted into the brake light circuit within the purple circle at the bottom of the wiring diagram,

[johnta1]

The lamps don't mention turn signal on them, just Stop and Tail. (at rear, nothing on front except parking)


Probably why one had to learn to use hand/arm signals?

[Bill Hanlon]

Google says turn signals were optional in 1955, so that is why they are not shown on that wiring diagram. Do you have turn signals? If so, the attached wiring diagram of how a 6 wire GM turn signal switch works would need to be inserted into the brake light circuit inside the purple oval on my previous post.

The single green line from the stop light switch would connect with the "from brake switch" contact on my drawing. The green line going to the left brake lamp would connect with the "LR turn & brake lamp" contact on my drawing. The green line going to the right brake lamp would connect with the "RR turn & brake lamp" contact on my drawing.

[Safari Larry]

Originally Posted by Bill Hanlon

Question for Larry: Were turn signals optional in '55 Pontiacs?

I was quite surprised to find that turn signals were an option in 1955 Pontiacs. They were standard equipment in 1956.

For 1955, "direction signal" was option TX and was included in option BA (BASIC group). See THIS LINK.

Wiring diagram for turn signals is in Shop Manual Accessories Section, page 14-5. For electric wiper, see page 14-7.

Bill, excellent job marking up the wiring diagram to show relevant circuits.

[Bill Hanlon]

The page 14-5 drawing of the turn signals and the switch agrees with what I said earlier, even showing 3 different drawings of the turn signal switch. One for left turn, one off and the 3rd for right turn.

[Safari Larry]

I screwed up saying "For electric wiper, see page 14-7". Electric wipers was not offered in 55.

When I read description of the electric wiper, I was looking at the 56 Shop Manual Accessories Section (LINK) on page 14-7

[Bill Hanlon]

I'm assuming Parkman51 doesn't have an ohmmeter and/or doesn't know how to use one. So .....

Remove both wires from the brake light switch.

Put a new, proper sized fuse into #9.

Does the fuse immediately blow?

If yes ...
... the problem is between the fuse and the dome light/trunk light. If you can find the connector with an orange box around it and unplug (or unscrew??) it, put in a new fuse and try again. Let me know results and we can continue down this path.

If no ...
... the problem is between the brake light switch and the brake lights. Let me know results and we can continue down this path.

I've fixed one oversight and added the orange box in this new version of the wiring diagram.

[Parkman51]

Lot of good information today. Bill's color-coded tracing of the wires was extremely helpful also, and you're right - 3 and 9 don't connect. Yet somehow the trunk light still comes on (???) when the parking lights are on, despite supposedly being on fuse 9. Perhaps at some point it was rewired into a different circuit? There's another weird thing about the trunk as well - it has two wires going into it, one of which dead-ends. See photos below, as well as a connector that seems to feed the trunk light wire currently. This connector doesn't appear to unplug or unscrew, it seems to be a type of permanent clamp fitting.



I did the recommended test - removing the wires to the stop light switch, and the fuse burnt out again immediately. (There's also a disconnected spring hanging around in there for some reason, but it didn't touch anything.)



Also filled and installed the air cleaner!

[Bill Hanlon]

Are you sure picture 4 is the stop light switch? It doesn't look like what I expect it to.

You didn't say, but given A/C, the under hood and trunk lights, and automatic transmission I assume the car has turn signals. The fuse blowing with the brake light switch disconnected says the problem is not down that path.

When you say "the trunk light still comes on (???) when the parking lights are on" does the trunk light stay on when the headlights are on?

Try pulling fuses one at a time and checking for operation of the trunk light to see where it gets its power.

[Parkman51]

Unless you mean a different switch, this is the switch under the steering column which interfaces with the brake pedal. CPR shows that it's the correct replacement part as well. On a related note, it's GREAT to hear that the problem isn't with the stop lights or turn signal - you know, the things I actually need. I don't mind losing the courtesy lights for a bit until I track the problem down. Do you think I ought to remove all the lightbulbs (2 courtesy lights, dome light) and try a fuse again, on the chance that the fault is downstream of one of the lights, or is it likely that the fault is upstream?

The trunk light I traced to fuse 3, actually - would explain why it activates when the taillights are on.

I do have an ohmmeter, but am inexperienced in its use.

[Bill Hanlon]

It is very unlikely that a bulb would develop a short. At least not for long. So removing all the bulbs and trying again is likely fruitless.

But the more I think about it, maybe a bulb is sitting wrong in its socket and shorting the contact to the case which is ground. It shouldn't take long to try. Pull all the bulbs, put in a new fuse and see if the fuse blows. If it blows you have a wiring problem between the fuse and the switches.

If the fuse holds turn on the dome light switch.
.................If the fuse still holds install the dome lamp.
,,,,,,,,,,,,,,,,,,,,,,,,,,If the lamp lights consider yourself lucky.

Now do the same thing with the trunk lamp.


The reason I thought that was the wrong switch is the way the switch is drawn on the wiring diagram. There it looks identical to the brake light switch that GM used in their Chevy and GMC trucks.