I've heard reports that fox urine will ward them off.
A friend used it for the same sort of problem (underneath her mobile.) Not cheap but a little goes a long way. She told me she just put a bit on a few rags and put the rags in their living space. They vacated pretty quickly and stayed gone.
I've heard the same with using ammonia on a rag as well, but never used it. Hav-a-hart traps baited with chicken legs always worked great for me.

Male human urine might work just as well, but you don't want to smell either the fox urine or the human urine. Raccoons are notoriously difficult to get rid of once they take up residence, as you know. Do you know anyone who has a killer dog that you could chain up near where they go in and out? Can you get any help from your county extension agent? In a lot of areas raccoons are recognized as a health hazard, since they carry rabies.

Wildlife Rescue people suggest soaking several rags in household strength ammonia and placing them in the space where the critters live (works for opposums, raccoons, skunks and squirrels, too).
I'd get busy and do it soon, as it's the time of year for baby raccoons. Once you're sure they're gone, you'll need to board up the area they are getting in through.

No no no. All of these home remedies, the mothballs, the ammonia soaked rags, the coyote urine, the ultrasonic sound emitters, they WILL NOT WORK, and if they seem to, it's because the animal moved out due to other factors.

If this is a female raccoon with young what will work is a perceived threat to the safety of her young. Thus, actual physical harassment to the mother and her babies will likely get her to decide to leave.

The only known actual substance that works, and it only works in a case of mother raccoon with young, is the use of male raccoon scent (gland or urine) to trigger a biological reaction by the mother to leave - a male raccoon will kill any young not its own.

Raccoons in buildings can be tough, and you might want to hire an expert for the problem

Here is a link that might be useful: Professional Raccoon Control - Get Rid of Raccoons

The previous post states that ultrasonic sound emitters do not work, that is not correct (most of the time). They have and do work very well as long as there is an entrance point that can be covered by the ultrasonic device. If you do not have such opening or there are babies, then you should call a professional animal control person to do the removal. If you want more information on a good ultrasonic device that works off of batteries then check out www.pest-control.bz