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There is not much too these important safety devices so fixing them is worth the time as you will likely have success without buying anything.
Check the relay and if you push the horn pad and hear the relay click, you can assume the issue is the horns themselves.
The horns are under the right headlight. To access them remove the right front fender liner and front splash shield. You may only need to loosen the fender liner to get to the top of the front splash guard. One bolt holds the horns bracket in place.
After you have access, test for 12 volts when the horn is pushed with the ignition on. If you don’t have 12 volts here start further upstream tracking the wires from the relay to the horns.
Both of my horns had failed. One quit years before the other.
One bolt at the top of the bracket holds them to the body.
Once off the bracket the back has an adjustment screw and the 2 connector bolts and 4 screws that hold the front on.
Once the four are out the inside is visible. Take the nuts off the connectors and the points are removed.
One screw holds them together. Be sure to take a pic or two along the way so you can get the parts back as they were. Doing one at a time is also a good idea. Clean the oxidation off and lightly sand the contact points. One of mine was oxidized together.
You can see there are four solder connections. On the horn that failed first, one wire was loose and all were poorly soldered so touch them up. I spent an extra hour finding this intermittent fault.
The electro magnet vibrates to create the note the horn is designed to produce and there is a great deal of vibration on these devices.
Once reassembled turn the adjustment screw until they sound sweet versus harsh. If the horn fails to make a sound, check across the two contacts for close to 0 ohms. If it shows infinity there is a bad connection somewhere inside.
excellent. I worked trial and error on these things, so this write up is a good keeper. It is hard to get them to honk again after taking them all apart.
Thanks for the encouragement. It seems obvious to me that many of us could not keep these cars running without the cooperation of people in this group. I did a refresh of my instrument pod last week and might not have attempted it if the articles written about doing so were not available. I really appreciate the advice given on the forum by the 20 or 30 core contributors like MrMerlin, Dr Bob, Porken, MainePorsche etc. and the parts suppliers like Roger, Int 928 and others. Being sort of self sufficient by habit I found the group after 24 years of owning my car through guys at Sharkfest Anaheim. Who designed and maintains the forum has the best Auto forum on the web.
Thank you Steve. The timing could not be more perfect since I have one of the horns which doesn't work. Currently when I press the horn it sounds like a Ferrari ! OUCH
Once I get to work on my car to get it ready for coming out of hibernation starting May 6th, I will have a few things to do and this will be on my list !
So based on this writeup I set out to repair my horns...got them apart and realized the resistance on the large (basso) horn is out.
took it apart and found out it does not have a circuit board in it. It has a break somewhere in the wiring, but the two coils apparently do not come out so no dice to repair. I also broke two of the tiny insulator washers that fit inside the metal tabs - beware!!
so my question is this - are the magnet assemblies for the horns the same regardless of Alta or basso? It looks like the only difference is the trumpet length. I am going to need to source a replacement for the driver asssembly if so.
anyone know if these horns were used by other manufacturers (easier to find in a pick and pull)?
I would have thought the 83 ans 86.5 both being S3 cars would have had the same horn inerds. So you are saying the Ohms across the contacts measured infinity indicating there is a break in the circuit somewhere. The wire on my coils is so beefy I can't imagine it could have broken. There must be wires versus the board mine has. You just might be able to figure out which wire / coil or where the break is. The small washers you spoke of are just insulators so a slice of plastic tubing could work to replace them. If you test and find the connection break you still might be able to fix it. Can't say if the coils are the same but My guess is they would be.
Best of luck, Steve
Here are a few pics for reference. When I get home this afternoon, I will report my resistance/continuity results for feedback. Maybe I am measuring the wrong places.
I have cleaned the contacts and spade connectors. Glad to know I can replace the tiny washers with a tiny piece of insulator.
Actually it looks like yours is a better built circuit than mine are. I wonder if this one was replaced once upon a time. I would open the one that works to compare your meter testing. Just open but not turning the adjustment screw wit the spring behind it. Being there are no electrical components to burn out I figured mine failed because the points were in bad condition other than the addition to the loose wire on the board. I bet you'll get this sorted out too. They are just a buzzer with a horn on it and the coils look really robust. Steve
Good you were able to restore function. The other option is to just replace them if repair turns out not so easy.
Note that the later models have non-trumpet horns.
Don't know about these early horns but the later stock horns were never very loud - you can replace them with Hella Supertones for a much louder honk for <$60 (pair). The later stock horns are good for 'apologies' but don't really say >>> ATTENTION!! <<< very well - the Supertones are rather better at this. Bolt up and electrically connect in the same manner - easy.
Well I made some progress. I finally got my large horn adjusted back with continuity. Reinstalled it and it works - just sounds really bad. Further adjustment does not really help that much - going too far "in" eventually causes the bar to stop vibrating, and too far "out" loses continuity.
But - I do hear two distinct tones now - better than just the high one. Supertones might be in the future.
Thanks Steve for the original writeup as it proved to be a great resource!
Hi Scott, Glad you got it working. To me fixing an original part is a win. I think a harsh tone must be from a secondary internal vibration. I guess what is important is being loud enough. Today cars are very sound proof and many people never roll down their windows or turn down their music. I wonder what DB level it takes to get most people who are using a cell phone to focus on their driving. Something painful for sure. I've been hit from behind twice by distracted drivers. Thank goodness not in my 928 yet.
Being a 12 volt device and in an easy place and mount offers many options. You could just install a complete horn like http://www.mpja.com/6-12VDC-Dual-Sou...info/18678+SU/ for $10 or get a other sound devices to your liking. Then there is always the Ahh ooo gaa horn or wolf-whistle from the J C Whitney parts catalogs. There could be devices that play a recorded messages or play music No need to follow the crowd .
I bet others in the group could make some great suggestions.
Cheers, Steve
04-27-2017, 01:59 AM
Repairing 928 horns
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