One thing that I've seen in regards to this error, is that isn't not always associated with the bulbs. It is true that there is a 99% likelyhood it is the bulbs, but that Preheater Assy does actually have 2 heating elements. One is the bulbs. The other, is located in the paper path to help warm the paper as it goes through. There have been on 2 occassions, where the bulbs are working fine, and the printer still gives this error. As it turned out, it was those paper heaters.
Granted, there is a slim change it's actually NOT the bulbs. One way to check is remove the right side cover. Turn on the printer and let it do a warm up. Just below the fan on that side is a cutout, and if you watch, you can tell if the bulbs are lighting. You don't HAVE to take the side cover off, but it does make it a bit easier to see the light.
Most likely, you could have repaired the printer by replacing the bulbs. You can find them at ANY lighting store. They are the tube type Halogens. 118mm running at 150W. Since this is the most common problem, we replace the bulbs, rather than replace the Preheat Assy. It saves the customer money for the service call. BTW, Xerox won't sell you just the bulbs. They make you buy the whole Preheat.
Timothy N. Couch
A1 Printech
Anchorage, AK