--- title: "120 Volt Shore Power Repair | Rancho Santa Margarita" description: "Transfer switch failures, GFCI trips, reverse polarity and burnt 50 amp inlets. Shore power repair in our Yorba Linda bays, serving Rancho Santa Margarita." focus_keyword: "120 volt shore power system repair rancho santa margarita" canonical: https://ocrv.me/services/electrical-repair/120-volt-electrical-systems/ kind: subService updated: 2026-07-29 source: OCRV Center --- # 120 Volt Shore Power Repair for Motorhomes and Fifth Wheels > Shore power faults live in **the inlet, the transfer switch and the pedestal**, not in the coach breakers. Alternating current work is billed at **$260 per hour**, $285 to $5,500+. ## What does 120 volt shore power repair cover on an RV? Shore power repair covers everything between the campground pedestal and the coach outlets: the inlet, the cord, surge protection, the automatic transfer switch, breakers and ground integrity. Rancho Santa Margarita owners bring these units to Yorba Linda because a hot skin fault is not something to keep testing in a campsite. - A 50 amp service is two 120 volt legs, not one 240 volt supply - Most no power complaints stop at the transfer switch contacts - Reverse polarity and open ground come from the pedestal, not the coach - Burnt inlet pins come from a loose plug, not from too much load ### Key facts | Item | Value | | --- | --- | | Price range | $285 to $5,500+ (1 to 22 labor hours at $260 per hour) | | Labor rate | $260 per hour (Mechanical and electrical department) | | Typical turnaround | 1 to 5 shop days (Inlet and transfer switch parts are usually stocked or next day) | | Written estimate | $150 (Credited in full against an authorized repair) | | Services tested | 30 amp TT-30 and 50 amp NEMA 14-50 (Both legs loaded and balanced before release) | Shore power problems have a habit of looking like appliance problems. The microwave quits, so the owner buys a microwave. Then the coffee maker on the same circuit does the same thing, and only at one campground. The appliances were never the issue. Something between the pedestal and the panel was. This side of the coach carries enough current to start a fire and enough potential to hurt somebody who is standing on wet grass with a hand on the entry door. We treat it accordingly. Nothing on this page is a job we encourage an owner to work through with a test light in a campsite. ## Shore power problems owners notice first The most common opening line is that half the coach works. Roof air runs, the microwave is dead, and everything came back to life the moment the generator started. That pattern is close to diagnostic on its own, because the generator and the pedestal feed the same panel through different paths, and the only device that chooses between them is the transfer switch. The second pattern is location dependence. Everything works at home and something specific fails at one park. That points upstream. Campground pedestals age badly, get backfed by rigs with bonding faults, and occasionally get rewired by somebody who reversed a hot and a neutral. A coach cannot be repaired into immunity from a bad pedestal, but it can be protected from one. - Works on the generator, fails on shore power - Fails at one specific park and nowhere else - A breaker holds until a second compressor tries to start - Discoloration or a melted rim on one inlet blade - Any sensation of current when touching the coach body ## 30 amp and 50 amp service are different animals A 30 amp connection is one hot leg through a TT-30 receptacle, and it gives the coach roughly thirty six hundred watts to work with. That is a single roof air and not much else. A 50 amp connection is a NEMA 14-50 carrying two separate 120 volt legs, which is why people who describe it as 240 volt service get confused about what their appliances are seeing. Nothing in a standard RV runs on 240. The practical consequence is balance. A coach with twelve thousand watts available can still trip a leg if both air conditioners and the water heater element ended up on the same side of the panel. We see this most often after a previous repair where somebody moved a circuit to the nearest open breaker slot without thinking about which bus bar it landed on. **What each service actually delivers to the coach** | Service | Configuration | Working capacity | Common failure | | --- | --- | --- | --- | | 30 amp | One hot leg, TT-30 receptacle | About 3,600 watts | Overload trips when a second large load starts | | 50 amp | Two hot legs, NEMA 14-50 | About 12,000 watts | One leg trips while the other sits nearly idle | ## The transfer switch is the part nobody thinks about Every coach with a generator has a device that decides which source feeds the panel, and it lives in a bay compartment where nothing draws attention to it. The contactor inside makes and breaks a large current, sometimes under load, and it does that every time a generator starts or a cord gets plugged in. Contacts pit. Eventually one set welds partly closed or stops closing at all. The failure signature is asymmetry. Both legs are present going in and only one comes out. Owners read that as an appliance fault because the affected circuits are scattered across the coach with no obvious relationship, when in fact they simply all sit on the same leg. Testing takes minutes once someone thinks to open the cover, which is why we do it early. > **warning:** A transfer switch that chatters instead of latching is arcing repeatedly inside a sealed box. That is a heat event in progress. Stop using shore power and generator power alternately until the unit has been opened. ## GFCI trips, open grounds and reverse polarity at the pedestal A ground fault device is doing its job when it trips. It compares current going out against current coming back and opens when the two disagree by a few milliamps, because that difference is leaving through a path it should not be using. In an RV the usual culprit is water: a heated hose connection in the wet bay, an outdoor receptacle after a storm, or a bay light with a compromised gasket. Reverse polarity and an open ground are different animals because they usually are not the coach's fault at all. A three light tester at a coach outlet reports the condition, and a check at a second known good source tells us whether the fault travelled with the unit. When it stays at the pedestal, we document the reading and hand the owner something concrete to give the park rather than a vague complaint. 1. Test the coach outlet with a polarity tester at a verified shop source 2. Repeat at the reported pedestal condition to see whether the fault follows 3. Isolate downstream branches to locate a genuine leakage path 4. Replace the affected device and re test with the wet bay wetted down ## Hot skin voltage and why we stop the job to chase it Hot skin is what happens when the coach body finds itself at a potential different from the earth under it. It is caused by an open ground somewhere in the path combined with any small leakage inside the unit. Nothing about the coach behaves strangely. The lights work, the air runs, and the only sign is a sensation when a person bridges the body and the ground at the same time. That sensation depends on how wet the soil is and what shoes somebody is wearing, which means the same fault can be unnoticeable one week and dangerous the next. We measure body to earth potential on every alternating current job that comes through, whether or not anyone reported feeling anything, and a coach reading potential does not leave until the ground path is proven. ## What shore power work bills out at Alternating current work runs through the mechanical and electrical department at $260 per hour. A wet bay receptacle swap with a re test is a short visit. Replacing an inlet, a cord end, a transfer switch and rebalancing a fifty amp load center across both legs is a substantially larger scope with parts on every step, and the range on this page reflects both ends honestly. Parts carry standard markup and sales tax applies to parts and materials while labor is untaxed. A written repair estimate is $150 and that amount comes back off an authorized repair in full. On jobs over two thousand dollars a deposit applies at authorization, which we state at the estimate rather than at pickup. > **price:** If testing shows the fault lives at the campground pedestal and not in the coach, the visit ends at diagnostic time. We would rather send a unit home with a documented reading than invoice a repair that fixes nothing. ## Surge protection, pedestal damage and your carrier A hardwired energy management system sits ahead of the transfer switch, watches voltage and polarity continuously, and opens the circuit before a bad pedestal reaches the coach. It is the one component on this page that prevents damage rather than repairing it, and units that have one rarely show up here with a cooked converter or a dead roof air control board. When a surge or a park wiring fault does take out appliances, coverage turns on documentation written before parts come off. Fault codes stored in the protector, the state of the inlet and the affected boards all matter, and once they are in a bin they stop being evidence. We photograph and record at teardown on every alternating current job for exactly that reason. ## Cost $285 to $5,500+, based on 1 to 22 labor hours at $260 per hour. Written repair estimate is $150, credited in full against an authorized repair. All work is performed in shop. ## Questions and answers ### Why does my RV work on the generator but not on shore power? That pattern points at the cord, the inlet or the transfer switch, since those are the only parts the generator path skips. A contactor with one welded or open contact leaves half the panel live. We meter both legs on each side of the switch while cycling sources. ### Is a 50 amp RV connection really 240 volt service? No. A NEMA 14-50 delivers two independent 120 volt legs to the coach, and nothing in a standard RV runs on 240. The distinction matters because tripping usually means one leg is overloaded while the other sits idle, which is a balance problem rather than a capacity problem. ### My bathroom GFCI trips every time I use a heated water hose. Why? Because it is detecting a genuine leakage path, usually moisture at the hose connection or in an outdoor receptacle downstream. The device is functioning correctly. We isolate the branch, replace the compromised component and re test with the wet bay deliberately wetted down. ### What causes a tingle when I touch my RV door at a campground? An open ground in the supply path combined with small leakage inside the coach leaves the body at a different potential than the earth. Whether you feel it depends on soil moisture and footwear, so a mild sensation is not a mild fault. Stop using the site and have the ground path verified. ### Why did the pins on my 50 amp inlet burn if I never exceeded the load? Heat at a connection comes from resistance, not from total draw. A blade that has lost spring tension or a set screw that backed off will run hot at half the rated current. We replace the inlet and the cord end together, since a heat cycled plug ruins a new inlet quickly. ### Does a hardwired energy management system actually prevent damage? Yes, and it is the one item here that prevents rather than repairs. Installed ahead of the transfer switch, it disconnects on low voltage, reversed polarity or an open ground before the pedestal fault reaches the converter and appliance boards. Coaches with one rarely arrive here with surge damage. --- Source: [OCRV Center](https://ocrv.me/services/electrical-repair/120-volt-electrical-systems/). Last verified 2026-07-29.