Right Rear Turn Signal Not Working...??

[Tom '74 911]

Hello,
I'm a bit stumped. My right rear turn signal is not working and I have been unable to diagnose the issue. The left rear works fine as do both fronts. Although I can measure voltage at the socket, the bulb does NOT flash when activated by the turn signal indicator switch or the emergency flasher switch. All other lights on the car work as they should.

So far I have:
1. replaced the bulb.
2. swapped bulbs from left to right & vice-versa. They all work on the left side, but not the right.
3. bent out the + tab in the socket recess slightly & made sure the bulb fits in the socket well - seems to.
4. used some fine grit sandpaper to clean out the socket.
4. used a multi meter and compared the voltage on the right side (not working) to the voltage on the left side (working) when the turn signal switch is activated - both sides appear to have similar voltage numbers - so I CAN read voltage with a voltmeter at the socket.
5. opened the back of the tail lamp housing and checked the voltage right at the wires, which seems good...
6. swapped in another tail lamp housing I have - same issue!

So in summary, my voltmeter seems to indicate that I have voltage at the wire terminals AND in the bulb socket itself when the turn signal is activated, but whenever I put a bulb in the socket, it does not illuminate. This is consistent with 2 separate tail lamp housings...

The only thing I can think of is that while I can read voltage at the bulb socket with a voltmeter, maybe it's just not high enough to illuminate the bulb? Could this be the case? The voltage does go up and down as the blinker relay turns it on & off and the voltage fluctuations on the non-working (right) side seems comparable to the voltage on the working (left) side...

What else can I be missing?

Thanks for your help,
Tom

[timmy2]

Get a $10 automotive test light and see if it lights up.
If it does, then likely a bad ground or bulb doesn’t make contact.
If it doesn’t, maybe it’s a bad connection at the 6 pin connector.
It could even be a loose connection at the front fuse panel.
The flasher wire runs directly from the front fuse panel to the 6 pin male connector, then to the lamp assembly via the female connector.

[Tom '74 911]

Originally Posted by timmy2

Get a $10 automotive test light and see if it lights up.
If it does, then likely a bad ground or bulb doesn’t make contact.
If it doesn’t, maybe it’s a bad connection at the 6 pin connector.
It could even be a loose connection at the front fuse panel.
The flasher wire runs directly from the front fuse panel to the 6 pin male connector, then to the lamp assembly via the female connector.

Hi Dennis,

Thanks for the response. I do have a test light & it DOES light up, confirming the voltage I see on my voltmeter... the light is not super bright, but it does illuminate...

So when I insert a bulb, it either doesn't have a good ground or has bad contact with the "+" tab in the socket?

I can not get a bulb to illuminate even if I wiggle it around in an attempt to secure a better ground connection...

Still stumped.

Thanks,
Tom

[Tom '74 911]

To add a thought...

the dude at my local FLAPS suggested a different replacement bulb than the stock one I showed him from the Pelican catalog... his version would be 'brighter' he said...

the Pelican catalog specs for a turn signal bulb are:
12v - 21/5W

the specs for the replacement bulb I have are:
V=13.5
W=25
A=1.86

I don't know what all the numbers mean exactly, but can see that they are not the same...

Could the replacement bulbs require more power to operate or 'open' than the original spec. (which is not being supplied?)

Don't know if that's logical, I'm not an electrical person... just know enough to be dangerous. Also, the replacement bulbs work fine in the left side turn signal socket and I think I have an original spec bulb that I tried and it did not illuminate either...

Thanks,
Tom

[timmy2]

If the bulbs work on one side, they should work on both sides.
Does the test light flash with the same brightness on both sides?

Have you unplugged and looked at the 6 pin male plug for corrosion?
Maybe the pins just need to be spread out for better contact.

Undo the wires for that side at the front fuse panel and inspect then reinstall?

Voltage but no current usually means a high resistance connection somewhere.

All other lamps in the assembly are at normal brightness? Then the grounds are good.

[Tom '74 911]

Upon further review, the test light is definitely dimmer on the non-working side. So I will check & clean the wiring & connections on that side & hopefully that will cure the issue.

On another note, my son suggested I check the blinker fluid level - that it might be low. I'll add that to the list too.

Thanks again for your patience & help,
Tom

[Tom '74 911]

Success! It was the blinker fluid, which I'd run dry...

Also, I checked the 6-pin terminal in the right rear of the engine compartment. I located the pin for the turn signal lamp and spread the male pins further apart just slightly. After reconnecting, it worked.

Makes me wonder how long my right rear blinker has been inop. ... probably a long while!

I would never have guessed that this would've solved the issue as there was enough current getting through the connection to light my test light and move the needle on my volt meter, but just not enough to illuminate the bulb... finicky!

Thanks for the support Dennis. I do still plan to get a wiring harness from you for my 2.7L engine rebuild at some point. I keep getting distracted by other projects.

Thanks,
Tom

[timmy2]

I’m happy you found it.
After 45 years the spring tension in the pin has relaxed like most people’s bellies of the same age.