Questions
The ones worth answering properly
Long answers, because the short ones are what got you confused in the first place. Several of these are things you can check yourself without us.
Questions and answers
How do I read the date code on my own tires?
Find the letters DOT on the sidewall and follow the string along. The last four digits are the week and the year the tire was built: 3421 means the 34th week of 2021. The full code is molded on one side of the tire only, so if the wheel is turned the wrong way you will find a shortened version and have to look at the inboard face. Take a flashlight. It is worth the five minutes, on somebody else’s rig as much as your own.
So how old is too old?
The industry guidance, and what tire manufacturers themselves publish, is to replace RV tires on age — the NTSB and the manufacturers put it at five to six years — regardless of how much tread is left. A trailer tire spends most of its life parked in the sun carrying a static load, and it fails from the inside out: the casing degrades where you cannot see it. Tread depth measures a wear process that mostly is not happening. That is why we read codes and not tread.
Why do you weigh the rig to set tire pressure?
Because the correct pressure is a function of the load on that axle, looked up in the tire manufacturer’s inflation table. The number molded on the sidewall is the cold pressure at the tire’s maximum rated load, which almost nothing is actually carrying. Set from weight, a rig tows straighter, wears its tires evenly and runs cooler — and heat is what kills RV tires. It is the most-skipped step in this trade and it costs one trip to a scale.
How often do trailer wheel bearings really need repacking?
Roughly annually, or every 12,000 miles, and sooner if the rig has been through water. On a trailer this matters more than almost anything under the hood of a motorhome, because there is no engine noise, no gauge and no warning — a dry bearing on a trailer axle announces itself by seizing, and by then the spindle is usually ruined too. That is a roadside recovery and a machining job instead of an hour on a bench.
My axles have grease zerks. Does that not do the same thing?
Not really. Pumping grease through a zerk fills the cavity but does not tell you what the races look like, and done carelessly it pushes grease straight past the inner seal onto the brake shoes, which contaminates the linings you were trying to protect. We pull the hub, clean the old grease out, look at the cone and the cup for pitting or brinelling, pack by hand, and fit a new seal. The zerk is a convenience, not an inspection.
Is smelling gas the test for an LP leak?
No, and this is the one that worries us most. The odorant is there to warn you about a large leak; it will not reliably tell you about a slow one, and people become nose-blind to it in an enclosed rig. The test is a timed leak-down on a gauge: the system is brought up to pressure, isolated, and watched for a fixed period to see if it holds. Either it holds or it does not, and that is a written result rather than an opinion. We also measure the regulator’s outlet pressure in inches of water column, because a regulator can pass a leak test and still be feeding your appliances wrong.
Why does my absorption fridge stop cooling when I park on a slope?
Because it has no compressor. It works by boiling an ammonia solution and letting it circulate by gravity, so it depends on being reasonably level to work at all. Run it badly out of level for long enough and the solution can settle and crystallize inside the cooling unit, and that is not a repair — it is a new cooling unit. If you are parked on a slope for a night, that is what the leveling blocks are for. A rule of thumb the trade uses: if it is uncomfortable to sleep on, it is too much for the fridge.
What is the difference between shore power, the converter and the inverter?
Shore power is the mains supply from the pedestal or the house socket, through the cord, into the rig. The converter takes that mains supply and turns it into 12 volt to run your lights, pump and fans and to charge the house batteries. The inverter goes the other way: it takes 12 volt from the batteries and makes mains for a few sockets — usually only some of them, wired deliberately. Three systems, three failure modes, and they all end at a socket, which is why they get blamed for each other. Half the inverter faults we are called about turn out to be an outlet that was never on the inverter circuit.
Why do my black tank sensors read full when the tank is empty?
Because the sensors are probes through the tank wall, and paper and residue bridge across them. Once that has happened they read high permanently, and no amount of dumping changes it. A proper flush — a real one, with water and time, not a bottle of blue liquid — sometimes clears them and often does not. Our advice is to stop trusting the panel and start counting days: you know how many days your tank gives you, and that number is far more reliable than the sensor ever was. We will still flush the tank properly, and we will still tell you if the reading did not change.
The slide seals look fine. Why are they a maintenance item?
Because the failure is not visible until it is expensive. A bulb seal that has dried out stops springing back, so it stops sealing at the top corners where water runs, and a wiper seal that has hardened scrapes rather than wipes. Neither looks dramatic. Both let water into the wall around the slide opening, which is one of the worst places on a rig for it to get in. Cleaning them and treating them with the right dressing — not something oily, which swells and softens the rubber — takes half an hour and buys years.
My motorhome sat all summer and now it runs rough. What is that?
Almost always fuel. Pump gas with ethanol in it does not keep — it draws moisture out of the air and it leaves varnish behind as the light ends evaporate. In a carburetor that varnish blocks the pilot jet, which is the smallest hole in the machine, and the symptom is exactly what you describe: it will start and it will not run cleanly at low throttle. On an injected machine it fouls the pump and the injector instead. We start at the fuel system, not at the engine, and the fix for next season is to run it monthly or store it properly with the fuel treated.
What actually needs doing on a trailer that nobody does?
The bearings, and the brake magnets. Grease has a service life whether the trailer moves or not, and a magnet worn past spec drags current without stopping much — a hub that has not been opened in five seasons will take the top end with it. Water is the other one: cross something deep enough and water gets past the vent lines into the front diff and the gearcase, where it turns the oil milky and starts on the bearings quietly. Also the CVT belt — it is a wear item with a service life, the clutch housing fills with belt dust, and a belt that has been slipped hot once is never quite the same again.
Can you just tell me what a repair will cost over the phone?
No, and we would rather say so than guess. A number given over the phone becomes the number you expect, and the gap between a guess and the truth is where every bad shop experience starts. What we can do is tell you what the diagnosis costs, what the inspection costs, and roughly how long the bay would need the rig for.
How far ahead should I book before a trip?
Three or four weeks if you can. That is enough time to inspect first and do any actual work afterwards, rather than doing both blind on the same day, and enough time to get a part that is not on the shelf. If you are inside a week, call anyway — but expect us to be honest about what can and cannot be finished properly, because we would rather turn work away than send a rig out half-done.
Do you come out to a storage lot or a campsite?
Yes, for inspections, gas tests, batteries, seals and small repairs. What the van cannot do is anything that needs the rig lifted safely, anything needing a scale run, and roof work in wind or in the middle of a Florida afternoon — sealant does not cure properly on a roof that is too hot to kneel on. We tell you which side of that line your job falls on before we roll, not after.
Still stuck
Ask the shop
If your question is not here, ring it through. Nobody on this end is trying to get you off the phone and into the bay — half these answers exist because somebody asked and then did not need us at all.