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Join Date: Aug 2003
Location: Napa, CA
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1976 wiring diagrams 911s? specifically horn related!

hey all -

been looking all over the place and I cannot find a wiring diagram specific to the 1976 model year 911s.....there are 1975 wiring diagrams, and 1977 wiring diagrams, but is the 76 a transition year that did not get well documented?

I have no owners manual, Haynes leaves out the 76 model year as far as I can tell, and a search here has not helped....

to further complicate matters, the car has been converted to a 1989 3.2L power plant, so lord knows what the electrical permutations were to get that to work?!?! Dink Farmer did the conversion, who has a pretty good reputation as far as I can tell.

Trying to get the horns to work, flying a bit blind at the fuse panel. I have 'clicking' in the relays when the button is depressed, but no noise from the horns. I swapped the relays around - same result. Jiggled all the wires at the horn connections - they are cruddy but appear to be solid on the attachment points.

The later horn diagnostics are somewhat useful, but I'm not sure what I'm working with - they do not appear to be the 964 horn configuration judging by the pics....

any help appreciated - as always!

cheers

tom

(sheepish double post, I landed in the engine rebuilding forum first....sheesh!)
Old 01-04-2015, 03:54 PM
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pic of 76 fuse panel

here is a pic of what I've got to work with -

18 post, 3 relays, 1976 911s
Old 01-04-2015, 03:56 PM
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ROW '78 911 Targa
 
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PM your email address and I can send you a link to my dropbox with '76 factory drawings in it.

The '78 schematic that our host has available to download is the same for the horn area schematics.
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Old 01-04-2015, 04:55 PM
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ROW '78 911 Targa
 
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Sent the link to you as per your PM.

Last edited by timmy2; 01-04-2015 at 11:23 PM..
Old 01-04-2015, 05:17 PM
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Same horn wiring diagram.........

Tom,

The horn wiring circuits for '75, '76', 77, and SC's ('78-'83) are the same. They have not changed a bit. The power to the horn relay comes directly from the battery and uses no fuse. It is connected before S18 and goes to the horn relay (J4).

Horn relay tests:
Check if you have power @ terminals #30 & 86 (hot all times).
Check if you get ground @ terminal #85 when you press the horn button.
Check if you get power to terminal #87 when you press the horn button.
Test that the horns are grounded.

Have you bench tested the horn/s? Before you go any further, test the horn/s first and make sure they work. Keep us posted.

Tony
Old 01-04-2015, 09:30 PM
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Tony -

thanks so much - great advice - I know I have power to the relays because it clicks when I push the horn button....so I assumed I had power to the horns but needed to verify.....

and so here's how it turned out (ie, here is the difference between people who don't know ANYthing and those who have done all this stuff before!):

1. Tried to see if there was power to the horns, but the multi-meter I was using was apparently kaput. so went to get a new mulit meter (which ended up being a while-you-are-in-town shopping excursion!).

2. Got the multi meter, and went to bench test the units - the shorter unit made NO sound, the longer horn made a little "ip" noise - that is all.

3. tested continuity - nada on either - For those who don't know, I used the multi-meter ohm settings to see if there was any needle movement when touching the contacts on the horn. Polarity does not matter - either side for red/black on the multi-meter leads, we are just looking for the needle to move.

4. recalled a comment about the adjustment screw from a link on repairing the 964 3.2 horns - and went about turning the screw on the back of the horns. Bear in mind, mine is a '76 tub, I had NO idea if the horns were the same as the 964 horns or not - turns out, NOT, the screw that the link said to turn 'counter clockwise' made no difference until I turned it 'clockwise' to the point that I had some continuity - whereupon the horn made a 'mew' noise when bench tested.

5. feeling somewhat bolstered in my confidence, I set upon tuning the horn to its loudest noise level while powering the thing and turning the screw. ahhhh - a really aggressive neutered sheep noise has been attained! "MEEEeeeeeWwwwww!"

6. Onto the shorter horn now - with my new-found knowledge of the 'adjustment screw' - and bingo - we have NOISE!

7. Replaced the horn assembly structure back onto the chassis, saving the attachment of the longer horn to the frame for later so I could get to the screw that holds the whole thing to the frame.

8. One final snug up on the screw that holds the longer horn to the frame - and - SNAP, I torqued the screw off. sigh. wire-ties for now, but I have noise that should astound people that i"m honking at since no one has probably EVER heard such a sound - a combination of an angry neutered sheep and a piccolo! Victory is mine.

The LEARNING POINTS:

1. ask for advice, and read the stuff that is out there. Had I not read about the 3.2 adjustment screws, I'd have taken the damn horns apart or purchased new ones.

2. make sure your kit is in order. duh. who knew multi-meters went bad? sigh.

3. do the easy stuff first - had I fiddled around with the adjustment screw I would not have needed to take the horn assembly off the chassis....

4. THANK THOSE WHO CONTRIBUTED TO THE SOLUTION!!

And so: Thank you everyone - another great session and another victory! I now know a little bit more about these great machines! And thanks for the wiring / current flow diagrams - that adds to the knowledge base for the '76 model year 911 cars!

all the best -

td

Last edited by tadink; 01-05-2015 at 05:19 PM..
Old 01-05-2015, 05:15 PM
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