1973 914-4 - - - - My wipers, horn, cigarette lighter and hot air fan won't work. I'm getting no current at fuse #8. I've replaced the wiper switch, checked the ground, cleaned all the connections at the bottom of the steering column and replaced the horn relay, still nada. I'm an amateur at this, especially electrical current flow. My turn signals work, which to me means I'm getting current to/through that switch. But no current out of the wiper switch with the key on and wiper switch on. What am I missing?

Your wipers don't work?
Does everything else work?
If power goes into the switch and does not come out you need a new switch.
If it goes come out of the switch, test the motor next

I re read this OP.
Get a meter to test for power at the top of the fuse at the fuse box first.
Then test the bottom.

Make sure you have power on the circuit coming from the fuse box first.

I did that - - no power either side of Fuse #8.

After studying the wiring diagram again and reading an old post on here from an owner who had same problem, I'm becoming convinced it's the horn relay. I replaced it with a new one, but since it was cheap and made in China, perhaps it was bad out of the box? How often does that happen?

There is power at the top of the fuse at the fuse panel.
Pull the panel down and see if one of the feed wires has fallen off.

Check why you have no power at the fuse. Everything else is downstream from there and won't work without power.
If just #8 has no power then there's probably a bad connetion in the fuse box or the terminals are corroded and need some cleaning.
Also, because of al ypur trial and error, I have to ask: How do you measure voltage at the #8 fuse?

with my handy multimeter. As I read the wiring diagram, the current flows from the switch through the horn relay then through #8 fuse, then out to the wiper motor among other things. If the horn relay is dead, no current flows. Everything that is fed from #8 fuse wont' work either, which is the situation I have.

I'm having my local 914 guru over tomorrow night to help me, so we'll get it solved!

srreality,
The power to fuse #8 comes thru the fresh air relay, J-13. Wiggle it around while the radio is on and see if you get intermittent contact. If so, you will need to clean the contacts of the socket and the prongs on the relay. You can spread the prongs very slightly to help get a good contact.
Tom

Are you saying/suggesting that the radio also gets power from that J-13 relay?

Short answer, yes.
Longer answer, there is no radio listed on the electrical drawings. I believe radio's were a dealer installed option and the easiest way to power the radio would have been off of the cigar ( cigarette ) lighter. That's how mine was wired also.
J-13 would have been better labeled as a power relay for accessories.
Hope this helps explain.
Tom

Thanks, Tom - - - I'm also a Tom...........I tried that just now. No go. I cleaned all the sockets and prongs on the relays attached to the fuse box board while I was there. I'm going to "map" where I get current in those relay sockets. I've checked and cleaned the grounds involved, but so far I remain stumped!!

PARTIAL SUCCESS!! Windshield wipers now work perfectly!! Found a prong in my new wiper switch not making contact with it's connector! Ever so slightly off. I hugely relieved that I don't have to change out the wiper motor!! Yet....anyways!

Now for the horns. I know the horn relay works and the parts in the steering wheel are right, so I need to check the connections at the horns and the grounds.

One step closer.............

Interesting thread, my car has a jumper wire that comes out of the fusebox to feed the same items; while it's been fine for the last six years or so, I'd like to have it wired properly...

And yeah, changing the wiper motor is indeed, a bitch.

Just curious - I'm having a similar (not identical) problem. What/how was yours resolved? Those pesky electrons.....