Since the fuses in an airhead are associated with the lighting circuits, confirm that those are good. They are located inside the headlight bucket.

On early airheads, there is a parallel connection inside the STARTER relay that is employed to distribute electrical potential to the functions that are down line from the starter relay. That would include the main switch. The place where this line of thinking goes bad is that you have electricity at the coil. I would get the wiring diagram laid out in front of me and start tracing the lines, starting with the battery, if I were facing this issue.

Posted by: @8053

On early airheads, there is a parallel connection inside the STARTER relay that is employed to distribute electrical potential to the functions that are down line from the starter relay. That would include the main switch. The place where this line of thinking goes bad is that you have electricity at the coil. I would get the wiring diagram laid out in front of me and start tracing the lines, starting with the battery, if I were facing this issue.

I do have the diagram, but it's in the Clymer manual, which I believe Snowbum disparages. 

Posted by: @rider17

After reading so many posts, and after a search here, I find it's my turn to ask for some help.

R75/7 --I've been working on it off and on for a year. It's had a tough life in it's 78,000 miles, some pulling a sidecar.

You seem to be allowing your experience with other motorcycles to color your opinion. 78K on an Airhead is nothing.

Today, I had decided to replace the front brake switch. After completing that, successfully, I thought I would tackle the turn signals. They had been working, then went down to only the left side, and now nothing.

Good idea. Allow me to encourage you to do your own repairs.

This has been said 100 times: Have you tried treating each connector within the turn signal system with an electrical contact anti-oxidation compound? If not, then why not?

I pulled the relay and replaced with another, and that was when the trouble began.

Which relay? There are 3 or 4 relays on an /7 Airhead. Was it one of the "mini-cube" relays? Did the schematic on the side of the relay exactly match the schematic of the one it was replacing? Did you try plugging the old relay back in to see if you could return to the previous system state? Did you apply electrical contact anti-oxidation compound to the male contacts on the relay before plugging it in? 

Typical automotive mini-cube relay

The mini-cube relay encompasses a family of about 25 relays, all housed within the exact same housing size, but each capable of a very different electrical job. This is why each has a schematic on the side. If the schematics don't match, then they are different relays and expecting it to perform the same as one with a different schematic is (well) simply stupid. 

I had no power-lights, dash, brake, nothing. The battery is new. I have power to the coil, but not to the ignition switch or the board in the headlight shell. Some of the bundles going to the headlight have questionable sheathing. I have wrapped them previously.

I apologize, but your description is complete nonsense. How can you have "no power, nothing" and yet have power to the ignition coils? Right off I'd have to say that the previous installation of the ignition switch is faulty.

I fear a break in the battery lead somewhere along the line. Is there a typical spot I should just split off the sheathing and look. Or should I just run a new wire from the battery to the headlight?

1. You should NEVER, EVER remove the insulation from a harness wire. You should sharpen the probe on your mechanic's electrical test lamp until it's as sharp as a sewing needle. Then you can easily push the probe through the insulation... which when you withdraw the probe will only leave a nearly invisible puncture, similar to a human getting a vaccine injection.  

Typical mechanic's test lamp

Stripping back the insulation leaves a scar on the harness which is the "beginning of the end" for a harness because there is NO WAY it can ever be repaired to prevent future short circuits. People that do this practice are called "butchers" and are in direct opposition of those trying to preserve classic and vintage vehicles, such as the Airhead. The First Law of dealing with ANY classic, vintage or historical item is always: "Do No Harm". We are merely the current 'keepers' of this classic item. Future generations will appreciate that we did not try to destroy them. 

2. It was common practice when these bikes were new for owners to add a main fuse on the RED wire leading from the battery to the ignition switch. Because this was added after the fact, they do not appear on any schematic. You should check for the presence of such a fuse, which will usually be located back near the battery.

3. The /7 had the under-tank front brake master cylinder. When parked on the side stand, corrosive brake fluid is allowed to leak onto the starter relay, there on the left side of the frame... opposite the voltage regulator. The (same) RED wire from the battery passes through not 1 but 2 contacts on this special relay on its way to the ignition switch. Any corrosion present on this relay socket OR inside the relay will inhibit proper electrical function for the ENTIRE electrical system. The diagram gives a simplified schematic for the battery-to-ignition switch connections...

Simplified /7 wiring

Of course, you should not be re-installing the Starter Relay for inspection unless the male contacts of the existing or replacement relay are coated with an electrical contact anti-oxidation compound. 

Hope this helps.

PS. What year bike are we talking about ?

@wobbly It's a 77. I have followed your advice and have been spraying every connector along the line with DeOxit as I have worked on each system. I also proactively sprayed all the board connectors in the headlight shell.

The relay in question is under the gas tank. 

Please tell me how the previous installation of the ignition switch is faulty, when last fall, all functioned correctly, and did before I undertook these repairs this week?

I'm thinking your reasoning about the starter wiring is a good avenue to explore, which I will do next.

Thanks for the help.

Posted by: @rider17

@wobbly It's a 77. I have followed your advice and have been spraying every connector along the line with DeOxit as I have worked on each system. I also proactively sprayed all the board connectors in the headlight shell.

This is good news. When you say you treated "every connector" then I would assume that also included the headlamp circuit board because those are also connectors. But that's an excellent practice and a very significant one that I wish you'd have given in the first post.

The relay in question is under the gas tank. 

Then that would be the Starter Relay, which has nothing to do with the Turn Signal system. The Turn Signal Relay is inside the headlamp shell, usually on the throttle side. The Starter Relay is a uniquely specific relay called a "Dual 87". The relay you installed most proabably has terminals labeled 87 & 87a (as pictured in my previous post) or even 87 & 88. Checking the side panel schematic as advised, you'll see that the old Starter Relay terminals are labeled 87 & 87. Small labeling change; HUGE internal wiring difference.

You can buy "Dual 87" relays on Amazon for under $7. Just snip off the mounting bracket.

Please tell me how the previous installation of the ignition switch is faulty, when last fall, all functioned correctly, and did before I undertook these repairs this week?

Because it's standard practice to go back to the previous repair and question it first. No where in your original post did you mention the ignition switch repair had been working successfully for 6 months. No where. All my suggestions are based on the information supplied, thus faulty information will lead to faulty assumptions. GIGO. 

I'm thinking your reasoning about the starter wiring is a good avenue to explore, which I will do next.

Now that we have more information, I'm 99.4% sure that once the relay schematics are compared, you'll find that 1) the wrong relay has been installed. And 2) that once the correct relay is installed (after treating the male contacts with anti-oxidation compound) that several issues go away. At that point the electrical system will start working to the extent that you can return to work on the Turn Signal system, none of which is under the fuel tank.

Hope this helps.

Here's the new version...

Posted by: @8053

On early airheads, there is a parallel connection inside the STARTER relay that is employed to distribute electrical potential to the functions that are down line from the starter relay. That would include the main switch. The place where this line of thinking goes bad is that you have electricity at the coil. I would get the wiring diagram laid out in front of me and start tracing the lines, starting with the battery, if I were facing this issue.

You were dead on here. That line from the starter relay had detached from the rectifier board. I guess it was not seated completely. I have clicked it into place and all is well--except I still have no signals!

Thank you so much!

OK, progress is always great news !!

Troubleshooting the turn signal system is just as straight forward. You'll need the correct tools and a highly disciplined (logical) approach to the issue. 

• The correct tool is, again, the mechanic's test lamp. This will allow us to quickly test for the presence of electrical power at numerous points. If those test locations follow the wiring of the Turn Signal system, then logic tell us if we have 'power' going into a wire or component, and no 'power' coming out of that wire or component... then the problem must be inside and caused by that wire or component.

Since we are searching for the presence of electrical 'power', the clip end of the Test Lamp must be connected to an excellent "ground" source, such as the Negative side of the battery OR an unpainted cylinder head fin. And to supply 'power' into the system, the ignition switch must be in the ON position. 

• Next, in order to follow the 'power', you need to understand how the electricity flows through the turn signal system. This is done by using a schematic. A schematic is a diagram of the electrical flow pattern, in the same way a road map tells you which road goes between 2 places. It is NOT a photograph or exact copy of the wiring, in the same way that a road map does not tell you where all the hills and stop signs are. Here's a distilled version...

?1

We DO NOT need to disconnect or disturb any connections. We simply need to use the needle-like probe on the Test Lamp to sneak in and touch the metal contact, hopefully light up to prove electrical power is present, and move on. We will not be unplugging any connectors, because that always carries the possibility of introducing MORE problems.

- First test point is the Green wire at the fuse to make sure power is coming from the ignition switch.

- Next will be the Green/Black side to insure the fuse is "good" and actually passing electrical power.

- Then will be the Green/Black wire going into the flasher relay.

- Then will be the Green/Yellow wire coming out of the flasher relay. (This wire goes into the cable leading to the handlebar switch.)

- Then we will need to find BOTH the Blue/Black and Blue/Red terminals on the circuit board inside the headlamp shell. (We Do Not need to disassemble the handlebar switch at this point in the testing.) As the handlebar switch is moved to Left and Right, electrical power should be detectable on the appropriate Blue/Black and Blue/Red terminals. (Be sure you are directly testing the wires coming from the handlebar switch cable.) 

- Each Blue/Black and Blue/Red wires from the handlebar switch go into a multi-terminal plug on the multi-color circuit board. One of those terminals is where the wire from the handlebar switch connects. The second terminal connects to the front flasher pod. The third terminal connects to the rear flasher pod. The forth wire goes to the dash  board TS indicator. All 4 of those terminals (on both colors) should test the same with the handlebar switch in the appropriate position for that color. (4 positions for Left side, 4 positions for Right side = 8 total terminals to test.)

- The last stop is inside the 4 turn signal pods themselves. The center bulb contact on all 4 turn signal bulb sockets should show power when the handlebar switch is in the appropriate position.

- The last test is for the return path from the bulb socket back to battery Negative (-). For this test, connect the Test Lamp to the Positive (+) terminal of the Battery and touch the Test Lamp to the outer part of the turn signal bulb's socket (where the bulb's "base" rests). If you have good "ground" path, then the Test Lamp should illuminate. 

I do not know, but highly suspect, that if one connector was mis-plugged on the multi-color circuit board, that one of the turn signal wires has also been mis-plugged as well. Working inside the headlamp shell is a dark place and the terminals on the circuit board are closely packed together. For that reason I use a floor lamp with a bright-white LED bulb to fully illuminate the interior, and make wire color identification 100% clear. Anyone can make mistakes inside the headlamp shell if they simply can't see.

Hope this helps.

[Edited to add TS indicator wiring.]

@wobbly I am familiar with circuit diagrams. Thank you for the diagnostic tree. 

Let me go back to the beginning of the problem, before the loose wire. 

When I first got the bike, I had only left signals. I replaced the relay (absurd price!) but was derailed by the loose wire. I did notice the fuse had burned. After reestablishing power, the fuse again went out. I believe the problem is downstream towards the lights, since I have power at the fuse (obviously, but too much.) I have ohmed-out the connections from the unpowered side of the fuse to each light, but don't see anything amiss there. Now that I think of it, I didn't check for ground from the fuse. BTW, I have double-checked the connections in the headlight. Where do I go from here? 

You have a "short circuit". IOW, you have an unplanned connection to ground that is too good. 

I test for "shorts" with an ammeter. Testing for shorts can also be done with a handful of fuses, but it gets very expensive, very fast. Choose your poison.

Known Facts

- Problem seems to be in the RH turn signals. LH turn signals seem to work.

- Problem seems to be in the Blue/Blk wiring. Blue/Red wiring seem to be OK.

- Since LH turn signals work, we are ~70% sure the handlebar switch is OK.

- From experience: Most TS switch issues happen in the TS pod or Bulb

Procedure

- Disconnect all the Blue/Red and Blue/Black wires from the multi-color circuit board inside the HL shell.

- Make sure you have enough light inside the HL shell. Ignition switch ON.

- Locate the cable coming from the handlebar switch and re-connect the Blue/Red wire to the circuit board. Observe the fuse (or ammeter). Follow this with the Blue/Blk wire from the HB switch. Observe the fuse. Next try the handlebar switch in both Left and Right positions. If nothing happens, then the fault is not in the handlebar switch. 

- Locate the 2 wires from the 2 front turn signal pods. If you do not have a RT or RS fairing, then these wires will come into the HL shell as individuals wires. Plug them up to the correct color on the circuit board. Observe the fuse. Next try the handlebar switch in both Left and Right positions. If nothing happens, then the fault is not in the front TS pods. 

- Unplug the multi-pin connector that is under the seat which connects the Tail Lamp to the main harness. 

- Locate the 2 wires from the 2 rear turn signal pods. These wires will come into the HL shell from the main harness (the largest cable entering the HL shell). (Since the 2 wires from the dash TS Indicator Bulb may also enter the same way, you probably won't be able to tell them apart.) Plug all 2 or 4 of them up to the correct circuit board color. Observe the fuse. Next try the handlebar switch in both Left and Right positions. Observe the fuse. If nothing happens, then the fault is not in the dash TS Indicator Bulb. 

- Re-connect the multi-pin connector that is under the seat which connects the Tail Lamp to the main harness. Observe the fuse. Next try the handlebar switch in both Left and Right positions. Observe the fuse. 

Notes

1) WHEN you isolate and detect the fault area, remember that the short could be in the wiring to the TS pod or inside the TS Bulb. So you'll need to stop and remove that specific bulb from the TS pod. If it's not the bulb blowing the fuse, then by default it must be worn, crushed, or mis-connected wiring that feeds the TS pod. It could be a wire that has had its insulation cut back for testing... butchery as we have discussed previously.

2) It is also very possible that the 2 wires have been connected to the TS bulb socket in the wrong order. Airhead TS lamp sockets have 2 connectors, power and "ground" return. The BROWN wire must be connected to the BASE of the bulb (the part with the 2 bayonet teets); the wire with the 12V power (Blue/Blk or Blue/Red) must be connected to the center contact on the bulb and no other. If those 2 connections are reversed, then you'll have a short circuit within the TS pod simply due to ignorance. Otherwise you're back to looking for crushed or butchered wiring. 

3) There are TS connections behind the Tail Lamp reflector. Remove the 2 tail lamp lens screws and look there too.

• I think it's important that you search this procedure (and the previous) for an Ohm/Volt meter. You won't find one. The issue is more easily located by simply following a logical sequence, starting at the Source and working back (step by step) to the end. There is also nothing random about the search. 

Hope this helps.

@wobbly After all that, I found I had pinched a horn wire behind the timing cover. There is now no issue with fuses.

Still no signals. There is power to the relay (which is new, from EME,) but nothing out. Curiously, the power into the relay fluctuates between 17 (!) and 11 volts. I can also hear it clicking, though the signals are not on either direction. Bad relay?

Update: I have working right signals. 

I had disassembled the handlebar switch after having the left signals flashing continuously. I discovered the green wire supplying power to the switch had broken from the soldered point on the assembly. I reattached, but have no continuity to the left now. It is not obvious how I can separate the rocker from the switch. Can I get some guidance here?

If the Green wire had become disconnected and if one side of the TS switch fails to work, then I'd conclude the switch has had a rough life. Those switches are full of tiny parts, and should only be disassembled over a workbench or table where there is plenty of light exactly because of the tiny parts.

If anyone previously ever tried to disassemble those switches on the bike, then it's almost 99.8% inevitable that small internal bits have already been lost. The only avenue of repair then to buy a good used switch for a /7 or later and replace what you have. The good thing is that ANY switches made after 1978/79 can be made to work. 

About 1987 they changed over to a single box connector, but you can cut off the box and go back and add discrete 1/4" spade contacts to each individual wire and end up with the pre-1987 turn signal switch configuration. The number of wires is the same and the wire colors are very similar, so connection doesn't take long to figure out. (I've done this before and as I remember the color of the Horn wire changed, so you have 1 open terminal and 1 wire remaining to connect to it. Pretty simple stuff.)

Hope this helps.