Are any Heurigen open on Dec 24?

Check back on this link when it is updated for restaurants open on 12/24. I highly doubt you will find any open heurigen open. Wherever you choose, make your reservations soon.

https://www.wien.info/en/shopping-wining-dining/restaurants/christmas-restaurants

Nobody goes to a Heurigen at Christmas. Not only that I doubt whether there are some open, it is the wrong setting for that event.

If you want to have a high class dinner in a fabulous ambiance, the I suggest to go to "Anna Sacher" restaurant, one of the best places in town. They have a special Christmas program (concert, punch, dinner).
https://www.sacher.com/wp-content/uploads/2016/07/Sacher-Wien-Weihnachtsmenue-2016-engl-web.pdf

If you prefer a more casual environment, I recommend "Plachutta Wollzeile", where you can get the emperor's favourite dish, "Tafelspitz". It is boiled beef, tender and juicy, for most Americans a very strange way of preparing this meat.
https://www.plachutta.at/en/plachutta_wollzeile/

In either case you should make a reservation as soon as possible.

" "Tafelspitz". It is boiled beef, tender and juicy, for most Americans a very strange way of preparing this meat. " Not if you had a Jewish mother who made pot roast !

Thank you for your replies and encouragement to secure reservations as soon as possible. I made reservations at Griechenbeisl.

We visited an excellent Heurigen a last week. Zum Martin Sepp is open on NYE, according to their website, but I would contact them about the 24th. It was very quiet the day we were there but it was open and the food was outstanding. And for guys like me who don't care for wine, they have beer as well. http://zummartinsepp.at/

The Heurigen is well-known for its wine drinking culture. Drinking beer (or coffee) there is considered a sacrilege by rooted Viennese people. Alas, more and more places make this concession to (sorry!) ignorant tourists.

I drank wine while there (when in Rome, as they say) but I'd always prefer a beer over wine. Next time I'll be that ugly tourist and just order what I like. 😉

According to Facebook, the Heurigen I recommend in my previous post is open on the 25th.

Yes, many places are open on the 25th. It is the 24th which the OP asked about. The 24th is the day that Austrians celebrate Christmas, so that is the day most places are closed.

Ah yes. My oversight.

Thanks for the info! I would love to go on the 25 as our reservations for Christmas dinner are on the 24. Would it be best take an Uber?

I'm not an Uber fan , but you won't need a taxi in any event . The # 38 tram goes from the Schottentor tram stop ( lower level ) to Grinzing ( last stop ) in about twenty or so minutes . From the tram stop , it's a short walk up Himmelstrasse , then bear right on Cobenzlgasse to Sepp .

Steven is right. Take public trans. UBER is great in the US though. I have a special deep-felt loathing for Chicago cab drivers. Taxis seem to be more professional in most of Europe but why spend the money?

Here are more detailed directions from the city center. I did this for another friend so it's easy to cut and paste here: (my hotel was in the Mariahilf district so adjust as needed or start from the U4.)

OK..Here's how to get to the Heurigen Zum Martin Sepp: Take the U3 (dir Simmering) change for the U4 at Wien Mitte-Landstrasse (dir Heiligenstadt) and get off at Heiligenstadt (last stop on the line). Take the 38A bus to the Grinzing stop. You will have to walk a block or two uphill and the restaurant is on the right. I missed this but Tina at the hotel said if you take the 38A to the end you will be rewarded with an amazing view of the city.

The # 38A bus continues up Cobenzlgasse along a winding road to the Kahlenberg viewpoint , indeed a striking view of the city along the Danube . For those with a literary bent , " The # 38 Streetcar " is poetically described by Elias Canetti in his 1930's memoir , " The Play of the Eyes "

From A to B

The simplest method to find the fastest route by public transport in Vienna between any two arbitrary points:
https://anachb.vor.at/bin/query.exe/en?L=vs_voranachb&

Also available as app for smartphones.