LF turn signals don't work - relay?

[Randy Webb]

The left front turn signals don't work on my 1973.5, nor does that bulb come on when the the emergency flashers are turned on. All parking lights and the other front & rear turn signals do work.

The bulb filaments look good and when I replaced the bulb anyway, nothing changed.

I am hoping this is a fuse.... but sounds like there is little chance of that as it seems other things would not work then. Any thoughts on that?

Also, if I have to replace the very expensive blinker relay, where is it located on this vintage (early) car? Is it up behind the instruments like on some of the later models? If so, how do you get to it? There doesn't seem to be any way to do it from underneath. Do I need to take out a gauge? Or should I go in thru the trunk ater pulling that carboard partition?

I'm hoping somebody just knows this off the top of their head. I couldn't find these answers in a search and hadn't really planned on a major reaearch project to figure out how to fix a turn signal bulb.

hell of a place to put a relay....

[Jim Sims]

My son and I have been through this with his 1973.5. If the other turn signals and hazard falshers work it is not likely to be the flasher relay. First, have you done anything recently to the LF front light housing bulb holder assembly? Jim

[Rot 911]

Randy, I had a similar problem on my 72. Over time the prongs that supply power in the light socket had been pushed so they no longer were in contact with the bulb. Had to take things apart to set them right.

[dhoward]

Ground.

[Randy Webb]

No, I've done nothing to the bulb or housing. The car sat out in the weather (rain) at a shop for many months while awaiting an engine and trannny transplant. It worked beforehand, but didn't when I got it back. After it stopped working, I removed the lens cover and changed the bulb, I did not check the tabs. I guess it is possible that one tab was bent but the other was not (??) - note that the parking light works - it uses the other filament in the same bulb.

Any other possibilities? It would be great if I didn't have to replace the flasher relay, but why would a bad relay be unlikely? It's the only thing I can think of that could cause this....

[Jim Sims]

Loose connection or bulb base prong or wrong bulb; also check connector through fender wall. Clean electric connection contacts and coat with dielectric silicone grease, then reassemble. One flasher does everything so if some bulbs flash it usually means the flasher is okay. Jim

[Randy Webb]

Thx - I'll open it up again, bend the tab and put some dielec. on the contacts. If that doesn't work, I'll look at the wire connections.

I take it that altho there have to be different individual metal strips in the relay, it would be rare for one to fail and not the adjacent one...

BTW, these lense have screws with Bristol slines on them. I posted about this before - pretty wierd... luckily I have a kit of oddball driver bits.

[jeff1hughes]

been there done that on a 71. Check the fuse first!!! Mine just had a bad contact in the fuse, bent the little tab up a little, cleaned the surface, and whala-- blinker worked!

[randywebb]

Ok, fuses, tabs, and contacts all seem fine and have been bent, cleaned, etc. to boot. Didn't help.

I pulled the relay (or "a" relay). The only relay I can find inside the left hand side dash gauges is just below them and is a round, black 5 pin relay with p/n 911.615.109.01 stamped on it. I thought the turn signal relay was a metal rectangular can above the gauges but there doesn't weem to be anything like that in my 73.5 (maybe that is for the later cars?). Does this seem like it is the turn signal relay?

And, if so, how do I test it now that I have it out? i.e. if I put +12 VDC to terminal x, and gnd terminals y & z.... etc.

Thx!

[jpnovak]

Do the left rear work? If so, then check the fuse panel, (#5 or 6 lower?) and see if both wires come from the same terminal. Check for 12 V on each side of the terminal. (front and rear wired together). IF this works then check for 12V coming out of the 6 pin connector on the fender well (above the battery). If you have 12V there and not at the bulb then you have a bad wire or connection. Next step is to check resistance from the 6 pin plug to the bulb. It might be easier to remove the backer plate from the TS assembly to test.

To find the blinker relay, turn on the right side blinkers you will hear the click behind the dual gauge. (oil pressure, temp). There should be a black rectangular relay there. Pop off the cover and clean the contacts. Then lube the magnet assembly. Should work great for another few years.

[randywebb]

Yes, the L. rear one works fine. I'll try those other tests.

Anybody know how ot check out the relay? I'd like a reward for the hand contortions I did this a.m. in my cold garage....

IF this round one isn't the turn signals, what could it be? It sure isn't the horn...

[fintstone]

If the flasher or turn signals work, it is unlikely the flasher is bad. If only one turn signal is out, it is most likely either the bulb/connection or the connection at one end of the wire or the ground.

If you want to do some testing…this is how you can start: The flasher has 2 different outputs..one for emergency flasher and one for turnsignals. If you have a voltmeter or test light you should test the flasher. First, find the flasher relay. Unplug it from it's socket. There should be 4 pins C, 31 49,49a. put a small piece of masking tape on the top of the relay and mark on it where each pin is...C,31,49,49a. Plug the relay back in about half way so you can still see each contact. Turn on your emergency flasher button and you should observe (pin 49)=12v(or test light on), Pin 31=ground (or test light off), Pin C switching between 0 and 12v (or test light flashing), Pin 49a flashing between 0 and 12v (or test light flashing). If this is correct, your flasher relay is good. Next, turn off the emergency flasher, turn your key to accessory and turn on either turn signal. You should get exactly the same.
The flasher should be behind the oil pressure/temp gauge. From under the hood, . It is a small rectangular black box with 4 connections located in your front trunk, behind the right hand blower valves (near brake fluid reservoir) hidden behind the cardboard-like cover for the blower and backs of gauges. It is not really a just a relay, but has one in it. You can probably hear it click when you turn on the flasher. It most likely says "blinkgeber" somewhere on it. If unsure, you can disconnect (unplug) the power to it...pin 49 and the flasher should cut out.
The unswitched power for it comes from the flasher button when the button is depressed (that is why you can turn on the flasher without the key). The switched power is available with the key to "on". That is why the turn signals need the key switched to on.

[Scott Clarke]

Randy-
Try tightening the screws that secure the wires at the fusebox. I had the same problem, and was fortunate to have accidentaly bumped the wire leaving the box. It was then obvious that it was loose. Two turns with a srcrewdriver was all it took.
-Scott

[randywebb]

Thanks Scott, finstone, Jamie - I'll try all these things. - Randy

[randywebb]

FWIW, and for the interest of the next person to have problems, here are the inards of the relay - there are at least 3 sets of contacts. A, B (the larger one) and C, which is underneath A and uses a much thicker piece of metal for it.

Pretty complicated little device -there are a least two semi-conductors in it. Maybe diodes, but I will guess they are drive transistors. Also 5 resistors, a large and small cap., and a small PC board (!)

Someone said to lube it - not sure where or what - can you expand on that?

I plan to use some emery paper on the contacts I can reach -- or maybe a points file (giving away my age I guess) and then test it as per above.


Can anyone tell me what the std. round black relay is in this space behind the gauges? It is just behind this rectangular one on my 1973.5.

[randywebb]

Well I give up on the pics -- What is wrong with this bbs?? Over an hour on a cable modem and can't upload at all....

[Jim Sims]

If the refurbishment of the relay doesn't fix the problem then check the base of the new bulb you recently installed; it should have two contacts at the bottom of the bulb. Jim

[HarryD]

Randy,

Did you get it fixed?

If I am not mistaken, all blinking is controlled by a single relay. If any thing else is working, then it is related to the circuit between the flasher relay and the lamp.


A few months ago, my rear lamp stopped working. When I disassmebled the housing I found it was the contacts that worked loose fromthe casting. But I also found out you can install the bulb (with two pins in the base) backwards and it will not work. Try turning the bulb 180 degrees and reinstall. Also, use a test lamp or voltmeter to verify power at the contacts in the lamp housing.

Best of luck.

[randywebb]

Thx Jim & Harry - I'd already check for the wrong type bulb. I also discovered that the buld is - shall we say - anisotropic. The little pins on the sides are offset relative to each other along the axis. I'm sure this is discussed somewhere Porsche's voluminous technical training manual on bulb maintenance.

Here's what happened - I plugged the relay with the cleaned up contacts part way in and tested 3 of the contacts from the driver's seat as per finstone's directions. To get to the other contact required that I pull the expansion chamber for the emissions system from under the cowl and that was a mutha. I finally got it disconnected from the hoses (hardened for 30+ years) and out. Then I was just barely able to test the other blade. It worked too. So, I pushed on the relay to seat it back down in the slots (assuming that whatever snading and filing I had done had fixed the relay). No go. I pushed and wiggled harder and it broke.

So, a new $37 relay is now on order. I hope it slides in a little easier....

Thanks for all your advice and help.

[coldstart]

Sorry to revive an old thread, but I was hoping to find the answer to my question.

How does the wiring harness detach from the front turn signal housing (72 911T)? I need to clean out the housing as the contacts for the driving and turn signal lights are out of place. Thanks in advance.