1999 Audi Sedan - Wipers stopped working......
 

....then after a few hours started working again without doing anything on my part.

Well, I replaced the fuse just un case but that wasn't it.

Any one have a clue what might have happened?

I'm a bit nervous in case the wipers quit again and I have to drive in the rain.

Well it couldn't be your fuse if they work intermittently, could it? ;)

It's your wiper motor going. I replaced mine with another used one, and that was 4 years ago (on the A6).

Make sure you get the correct one that fits your car.

Do a search on replacing the wiper motor, plenty of info.

I guess I wasn't very clear in my post.

Wipers stopped working.
Replaced the fuse
Still not working
I did nothing else to try to find the issue or fix it since I was on the road
A couple of hours later, turned them on again and they worked and have ever since.

Is there any way to check the motor?
Electric motors don't wear out and they also don't usually start working again by themselves after they quit.

You were pretty clear, as was I in my answer.

When you were replacing the fuse, was it blown? I'm guessing not. What good was it to replace a fuse that wasn't blown?

You can try replacing the relay, but what you're describing is a symptom of the wiper motor failing.

And one more thing: did you try searching the forums for "wiper motor"? Make sure you search for the phrase in the Title of the post, not the Entire post - you'll come up with dozens of threads, you can answer your own questions.

No, the fuse was not blown but fuses do age.
So replacing it was a perfectly normal thing to do especially when the fuse is that old.

And I did search in the forum before I posted - there are a number of threads about wiper problems but nothing where the wipers stopped working and then, for no apparent reason, started working again.

I took the car in this morning to an Audi specialist for an oil and filter change; I mentioned the wiper issue to him and he will take a look to seewhat might have been the problem.

An "aged" fuse will blow due to the heat cycling it experiences. Those type of fuses have two only options, working or blown, because there is only one bi-metal strip that allows current to pass. Other fuses, like industrial 480V fuses, can fail just the same but they typically have more than one bi-metal strip. If one strip blows in the fuse the device it powers may still function. But once it sees a current spike, especially on startup, it'll blow. So, all or nothing... ...perfectly normal if not blown, no. Now from a preventative maintenance perspective, sure after 10-15 years replace all the fuses... ...or just replace them if/when they blow. :)

As a matter of fact, these electric motors do fail. They fail in several ways. Pick one or more:
1. Commutator wears out brushes or a bar on the commutator shorts or opens to the armature.
2. Field coil opens or shorts or permanent magnet comes unglued from casing.
3. Bearings fail, armature locks up.

In the case of a wiper motor operating intermittently it could be a dead spot in the commutator, vibrations or whatever may move the armature to a live spot and it works or more likely you have a bad ground somewhere in the control circuit to the wiper motor or a bad wiper control stalk switch.

Don't confuse bimetal strip in circuit breaker with a metal strip in a fuse.
Sure, the metal strip in the fuse is an alloy, but it is not a bi-metal strip that is designed to bend with different temperature coefficients of expansion of the different metals and thereby open a circuit when too hot/too much current.

I'm not saying that electric motors don't fail, what I'm saying is that they don't fail for several hours and then just start working again as if nothing had happened.

I wasn't driving the car when this happened, but the following supposedly happened:
Light drizzle, driver turned on the wipers - nothing happened.
Tried the various positions, slow, fast and single-wipe, none of them worked.
Drove for an hour, tried the wipers again, still didn't work.
Switched horn fuse with wiper fuse, wipers still didn't work, horn worked with the "wiper fuse", so the fuse was fine.
Tried wiper every few hours or so - didn't work
Next day, about 20 hours after the wipers were first noticed not to work - turned on the wiper switch, they worked as if nothing had ever happened.

This happened about a week ago, wipers have been working fine ever since.

Had the Audi mechanic check the wipers, linkage etc. yesterday when I had the car in for an oil change - he could find nothing wrong.
Wipers were running at a good speed.

So.........all I can do now is keep an eye on it and try the wipers every once in a while even with no rain to see if the problem comes back.