Mary Lou and Herb Humphries sold their home in Massachusetts last July to travel the country full time in a new, nearly $500,000 motor home. But so far, they haven't gone much farther than the dealership lot.

Since they bought the luxury Beaver Patriot Thunder, made by Monaco Coach Corp., they have faced problem after problem, including burned-out fuses, mold, misaligned doors, and a broken alternator that caused a breakdown on the highway last fall. Since buying the motor home last August, the Humphries, who live in the coach, have split most of their time between the dealership and the manufacturer's service facility, both in Florida.

"We've lost nine months out of our retirement life because of this motor home," says Ms. Humphries, who says the coach has required about 400 repairs (many of those repeats), covered under warranty. "Our dream has literally turned into a nightmare."

Sales of recreational vehicles have jumped in recent years, boosted by the large number of baby boomers reaching retirement age and wanting to take to the road. (Late last month, the movie "RV," starring Robin Williams, opened No. 1 at the box office.) According to the Recreation Vehicle Industry Association, 384,400 RVs were shipped to dealers last year, up about 4 percent from a year earlier and a 27-year high. Motor homes, which can sell for as much as $400,000 or more, make up about a fifth of the RV market and towable trailers, which generally cost anywhere from $5,000 to $100,000, about 80 percent.

But as summer travel season starts, complaints about recreational vehicles are mounting. Some of the downsides: So-called lemon laws, which guarantee consumers replacement motor vehicles or refunds after a certain number of problems or days in the shop, vary by state and often don't apply to RVs. Consequently, RV owners, stuck awaiting repairs, often have little legal recourse. Gas prices also remain high.

The RV Consumer Group, a nonprofit group that rates recreational vehicles for safety and handling, says it gets about 100 complaints a month related to structural deficiencies with RVs, up from about 50 complaints a month a decade ago. The Council of Better Business Bureaus Inc. received 844 complaints about RV dealers in 2005, repair issues being among the most common, up from the 488 complaints it received in 2000.

Nationwide law firm Krohn & Moss, which specializes in lemon laws, has received nearly 1,500 inquiries about problem RVs since it started an online free case review database two years ago, and it has started a special division devoted to RV lemon cases. The magazine of Escapees Inc., an RV-owner club based in Livingston, Texas, included its first article on the topic of lemon RVs in its May/June issue.

RVs often have more problems than other vehicles because they are made in much smaller quantities than cars and without the same sophisticated manufacturing methods. Unlike cars, motor homes are made by multiple manufacturers. Auto makers typically build the engine and transmission. RV manufacturers then assemble living quarters, often by hand, increasing the chance for human error. More RVs on the road also means a greater chance of problems.

According to the National Highway Traffic Safety Administration, there were more than 100 recalls involving RVs last year, up from 83 in 2000, for defects varying from faulty microwave ovens to improperly installed furnace exhaust vents. A 2005 survey commissioned by the RV industry found that 64 percent of motor-home owners brought their RVs in for services beyond a routine visit, most often citing problems with the interior, appliances or electrical components. A quarter of owners were dissatisfied with how problems were corrected.

In response, legislators in Michigan, Pennsylvania and Montana have introduced bills that create RV lemon laws or expand existing lemon laws to include RVs. According to the law firm Kimmel & Silverman, lemon laws in 17 states and Washington, D.C, don't cover RVs at all and those in 20 states cover only their motor-vehicle components. Motor homes are covered in the lemon laws of 13 states -- but often only those under a certain weight.

Manufacturers argue that buyers today unfairly expect RVs to meet the same quality standards as cars when they should be comparing the coaches to homes. RVs tend to have more problems than cars "because of the nature of it," says Richard Coon, president of the Reston, Va.-based Recreation Vehicle Industry Association, which represents the RV makers and component suppliers. "Put your whole house on a truck bed and drive it down the street and things start happening," he says.

While the RV industry has lobbied against including RVs in lemon laws, manufacturers and dealers say they are working to improve quality and service.

In regard to the Humphries's problems, a spokesman for Monaco Coach says the company doesn't comment on specific cases. But Monaco has instituted an inspection system for each vehicle that comes off the assembly line. Coachmen Industries Inc. has opened a center in California to service vehicles on the West Coast so that customers there don't have to rely on dealers for warranty repair work. Companies such as Winnebago Industries Inc. and Thor Industries Inc. are focusing on "lean manufacturing" processes that cut down on how often parts are handled during production, reducing the chance of damaging them. Thor Industries says many of its brands have put in place electronic warranty processes to speed up the repair-approval process.

In states where RVs aren't well covered by lemon laws, consumers who end up with problem motor homes often have few choices other than to sell the RVs at a loss or postpone trips and make repairs. The good news is owners often aren't responsible for paying for repairs during the first few years of ownership. RVs are generally covered under one- or two-year base warranties and additional ones for various parts.

Earlier this year, the Recreation Vehicle Dealer Association started a new pilot certification program for dealer service managers to make them more effective at getting the units serviced correctly the first time. The association, which has had certification for technicians since the early '90s in a joint program with the Recreation Vehicle Industry Association, has also released a guide for parts personnel to help them increase their expertise.

In Florida, where the lemon law covers only the motor-vehicle components of motor homes, RV makers are funding a new mediation program operated by an independent third party, in which RV owners and manufacturers try to reach a settlement before going through the lemon-law arbitration process. During mediation, owners can bring up issues that go beyond the lemon law, such as problems with leaks in the living quarters. As of last July, they also can bring them up in arbitration if manufacturers agree (so far, none have). The Recreation Vehicle Industry Association says it would like the Florida program to be a model for other states.

Groups such as the Family Motor Coach Association and publications such as Trailer Life Magazine have intermediary and ombudsman programs that will help RV owners solve problems they may be having with dealers or manufacturers.

Attorneys say they can defend RV owners using other laws, such as a federal law that provides protection to buyers of consumer products under warranty, but say they turn away many RV owners because such cases are harder to win, expensive and can take years. RVs also don't have many of the protections homes do, such as state laws requiring owners to disclose problems and prepurchase inspections.

Sales of motor homes have started to slow in recent months, partly because of high fuel prices. Motor-home retail sales fell about 21 percent to 7,328 units in the first two months of this year, compared with the same period a year ago, as RV buyers delay purchases or opt for towable trailer models.

To attract buyers, manufacturers and dealers are rolling out a host of discounts. This summer Thor Industries says several of its brands will be offering gas cards to attract buyers. Terry's RV Center in Frankfort, Ill., rolled out a loyalty program for customers that allows them to redeem points earned on service and parts for perks like free RV washes. Lazydays, an RV dealer in Seffner, Fla., where the Humphries bought their coach, just launched a membership club for owners called Club Lazydays that provides benefits like breakfast and lunch when customers are on the premises for repairs and 30 percent discounts off area attractions.