like any table you want to take a good look at the playfield look for broken plastic covers
and the ramp to the left.
They made over 7000 whirlwinds in 1990 check out the Pinside Achive section for this game to give yourself a good idea and what others say about it.
Most of all see how it plays - good luck doublezo1

Make sure it has the topper. See if the fan works. There are some replacement motors available (I think from Grangier) but I think the shaft is a different diameter than the fan blades.

Check that the displays are working. The 47k ohm resistors on the power supply can go bad and make the displays inoperable. It is an easy fix and can restore what appear to be bad displays for <$1.

Check for cracked ramps.

There are usually broken plastics on the sides of the ramp and at the three bank drop targets. You can buy a replacement plastic set from Mad Amusements.

You can buy new decals for the spinner discs and other areas from Jeff at Classic Arcades. Get them from his eBay store, not the web site.

Hopefully it will have full Mylar, which will spare you a lot of playfield wear. But there may be wear around the spinners even with Mylar. If it has a Diamond Plate playfield, you've struck the jackpot.

There's usually wear at the right Cellar Hole.

Stand up targets are often broken, no biggie but don't be surprised.

The optos for the drop targets are often not working. Sometimes it is an easy fix as the wire inside the plastic housing breaks and it can be easily repaired without having to buy a new opto. (This is what I did, I have pics if you have this problem.)

The upper right flipper is often weak, making it impossible to hit the Million ramp shot.

If I can think of anything else, I'll add it.

If it's not diamond plated, check for wear around the bumpers, as the mylar doesn't cover those areas completely. Also check the left ramp entrance as it is usually broken, unless there's a cliffy on it. If there isn't a cliffy and you get it, get one for it.

That's all I can think to add, except if you do get lucky and find a diamond plated game, I'd jump on it for sure.

Good luck with it, great game