RV Holding Tank Sewer Odors

I recently purchased a 2003 motorhome. I have emptied the black water holding tank and noticed the tank is quite odorous still when driving. I do not notice the odor when the unit is parked. Any suggestions on how to correct this problem will be helpful. Elaine, (Elk Grove, CA)

Elaine, the first thing you should do is fully flush out the holding tanks with copious amounts of fresh water. Keeping them rinsed after each evacuation will help minimize holding tank odors. You only state the tank was evacuated, not if you’re adding fresh water afterward. Also, if you’re not yet doing so, only add enzyme-based tank additives to help break up the solids in the black holding tank. But probably the best thing you can do is to replace the existing sewer vents on the roof with Xtreme Vents. 

I believe I’ve mentioned them before, but it bears repeating. These aerodynamically designed roof vents capture the breeze when the RV is standing still and takes in ram air while driving. Xtreme Vents operate on the venturi principle of air being passed over a tube. As air passes over the open end of the vent pipe, it draws air and odors from the tank. This will help eliminate odors by literally “sucking” them out of the tank. This is extremely helpful, (get it?), especially when a 14-inch roof vent is located very close to the sewer vent. The Xtreme Vent will, thankfully, eliminate that design flaw with some floor plans. And remember, there are just as many odors emanating from the gray holding tank as the black tank. I consider it one of the best add-on components available.

RV slides barely moving

We have just purchased a 2005 coach with three slides, which have rack and pinion electric mechanisms. The large living room slide lifted up awkwardly, went out less than half way and made loud noises. We put it in and tried again and it would only go out half way and made both clunking and clicking noises. The top (of the room) was barely out and the bottom was way out of whack. We tried lubricating it but it seemed to get worse. Now it makes loud clicking noises only and barely moves at all. It sounds like the gears are out of sync. Is there a way of fixing this without waiting and trying to find a repair shop? We are on the road full-time.
Rick, (Westbank, BC)

Sorry to hear that Rick, I wish I could be more encouraging, but unfortunately due to the complexity of slideout mechanisms and room adjustments, I’m at a disadvantage without seeing it with my own eyeballs. Any attempt to adjust slide mechanisms and troubleshoot operational errors should only occur after a complete inspection. And quite frankly, oftentimes repairs cannot be performed in the field. Specialty equipment may be needed in order to effectuate a complete repair. I would, however, suggest you contact a certified mobile RV tech if one is available where you are currently located. There is a chance he might be able to unbind the mechanism, barring any physical problem with broken gears or and issue with the motor itself. Also, the proper troubleshooting strategy depends on the manufacturer of the slideout mechanism; some are proprietary. Perhaps it is nothing more serious than a physical binding or a simple alignment issue. Wish I had more encouraging news, but unfortunately these types of repairs are not usually for the Do-It-Yourselfer.

RV Air Conditioning Question

We have a 2004 Jayco 5th wheel trailer with an air conditioner that cools us and then waits a long time before it starts up again.  We are cooled then hot.  We have asked our local camper sales and service to help, but they say there is nothing they can do.  Do you have any suggestion, or do you think  it just the nature of the beast? Kathleen, (email)

Kathleen, it really depends on the type of thermostat equipped with your air conditioner. I’m assuming you have a roof top air conditioner. Some units have the thermostat located on the interior shroud of the air conditioner itself, while others have a wall thermostat for both heating and cooling. It’s possible either type of thermostat is out of calibration. If you have a wall thermostat, be sure it’s mounted about half way up the wall. If it’s mounted too low, it will take longer for the sensor to pick up the fact it’s getting too warm in the unit.

If the thermostat is located inside the air conditioner ceiling cowling, be sure the sense probe is not contacting any other metal component and that it is clean. Oftentimes, cooking oils or cigarette smoke can coat the tip of the probe, thereby lessening its functionality.

Here’s a picture of the sense probe. (You’ll have to remove the ceiling cowling to locate it). It should be positioned directly in the flow of the return air to the unit and not be touching any other metal component. It should just hang there, sensing the air returning to the air conditioner.

Also, be sure the thermostat is turned all the way to the coldest setting. If the unit indeed eventually cools the coach, the air conditioner itself is probably okay. Some thermostats are also adjustable. And there are additional tests that can be performed before fully condemning the thermostat, but these are better left to the professional RV service technician. Let me know the brand and model number if you need any further assistance, but check the position and cleanliness of the sense probe first and be sure it’s turned to the coldest setting.    

Timely Holding Tank Evacuation

I recently purchased a 2001 Jayco motorhome and the problem I have concerns the amount of time it takes to drain the gray water tank. The black water drains very quickly but when I drain the gray water the bulk of the water drains quickly but it take several minutes (up to 10+) of a steady trickling to drain completely. I've had the tanks flushed and scoped and I've personally inspected the drain valves and they are fine. I've also driven the right front tire up on blocks to help but nothing seems to work. Could you please give me an idea as to what the problem is? This is rather bothersome when others are waiting in line behind me. Carl, (Renton, WA)

Barring any severe blockages inside the holding tank Carl, it is apparent a venting problem exists. As a holding tank drains, air must enter the tank from above. All holding tanks must be vented through the roof of the RV. In some cases, the vent pipe can fall down inside the tank, immersing itself in the contents of the holding tank. This effectively blocks off the vent, thereby eliminating the venting action of allowing air to enter as you try to empty that tank. This is why it seemingly drains normally at first; the weight of water forces the initial gushing. Venting allows air to enter the tank.

Here’s an analogy….place a drinking straw into a glass of water. If you simply lift the straw out of the glass, the water inside the straw drains out as you lift. Now place your finger over the open end of the straw and lift it out. The water remains trapped inside the straw until you remove your finger from the end. Liquid entering the holding tank must displace the air when draining into the tank and air must enter behind the contents during draining of the tank itself. That vent through the roof must work in both directions.

From up on the roof, remove the cover for that holding tank vent. If the ABS piping is not protruding above the roof a couple inches or so, chances are the vent has slipped down into the tank and made contact with the contents. In some cases, you can re-attach it correctly from inside the RV; in other cases, the holding tank must be partially dropped in order to repair that vent connection. A thorough inspection will reveal the best method. The other possibility, albeit slight, is that the manufacturer plumbed the drainage system without the requisite slope; water cannot flow uphill. This may not be your problem since you’ve raised the coach to try it, but it may warrant a closer look.

RV Water Heater Check Valve - What For?

In a letter in an earlier issue, a question was asked about no hot water. I had the same problem and discovered a check value in a fitting on the outside of the hot water tank had failed. No one at the local dealer could tell me why there is a check value there and I could either replace the valve or remove it. I removed it and have not had a problem since. If you find a reason for the check valve being there please let me know so I can re-install one. In any case, that sounded like what that other question was about. Jim (email)

Typically there are three check valves in the fresh water system; one at the city water inlet (to prevent pump pressure from forcing water out the entry), one at the outlet of the water pump (to prevent city pressure from backing through the pump and filling the water tank and one at the cold inlet to the water heater. It’s there to prevent hot water from migrating back into the cold water system. If a branch cold line, say to the toilet, is plumbed (tee’d) into the cold line too close to the back of the water heater, it could siphon hot water out of the tank and into the toilet when it is flushed. It’s happened before! As long as you have no branch cold lines tee’s near the inlet to the water heater, you shouldn’t experience that problem. Having a check valve at the cold inlet to the heater also prevents mineral deposits and residue from backing into the cold system from inside the water heater. As long as you flush the water heater out once or twice a year, this too, shouldn’t be a problem. But to be safe, it might be wise to reinstall one when you get a chance.

Engine Removal

I have some friends that own a 1991 motorhome that is built on a Chevrolet P-30 chassis. It has the 454 engine that has failed. I am an ASE master mechanic but I don't see an easy way to get the engine out of this thing. My best guess is out the driver's door after removing the steering column but I'm not sure. I don't want to start this project without knowing. Any help would be appreciated.
Danny, (Archdale, NC)

Danny, though I’m not an engine/chassis/driveline guy (my expertise has the house portions as the focus), I have seen shops struggle mightily trying to remove the block. A lot depends on the design and construction of the front cap. In some cases, the entire cap, or a portion thereof, can be removed so the engine comes straight out the front. Other times I’ve seen them raise the motorhome and drop the engine down. This is effective if the front portion of the frame has rail extensions that can be removed. And as you mention, up through the doghouse and out through the driver’s door with a cherry-picker. I don’t envy you one bit! It’s a big job however it comes out.

RV Air Conditioner Will Not Shut Off

We have attended your seminars at the Hershey RV Show for the past several years and now find ourselves needing an answer to a dilemma with our Newmar 5th wheel. The first summer we had this RV the Penquin air conditioner needed to be replaced because it would not cool. Last year we were using the air conditioner in the automatic mode and it functioned okay but when it came time to turn it off we could not turn it off with the on/off switch beneath the thermostat on the wall. However, we could use the Off Mode to turn it off. We had an RV repair company replace the thermostat on the wall, but that did not work. Then the repairman went on the roof of the RV, opened the A/C cover and tapped the contacts with the end of his screwdriver and that allowed the on/off switch on the thermostat to work. When the repairman left the A/C was switched off. Later that evening the A/C came on by itself and we were not able to turn it off at the switch, again. We contacted the repairman and he replaced the "motherboard" on the roof unit; however, that did not work either; the thermostat switch will still not turn the unit on or off. Do you have any recommendations on how to solve this problem? Joseph, (Mount Wolf, PA)

Joseph, it sounds like you may have some shorted wiring between the thermostat and the roof unit or an incompatible thermostat. Faulty boards are more common than they should be, however, a technician can use jumper wires to verify if new wiring on the control circuits between the wall thermostat and the A/C is needed. The temporary jumpers will isolate the problem to the conductors or to the board itself. The tech will also have to verify that the new thermostat is compatible with the air conditioner; not all are.

I wish I had more concrete info for you, but it without the wiring diagram and the part numbers, there’s no way to verify via long-distance. I’m not sure where in PA Mount Wolf is located, but I have a Master Certified technician in Eastern PA who might be able to help. Give Ron Donachie a call and see if he can make a service call for you. Here’s his contact info:

Ron Donachie
Ron’s Mobile RV Services, Inc.
Serving Eastern Pennsylvania
484-225-8211
rondon@ptd.net

Thanks again for your email. Do let me know if Ron can help you out!

Galvanic Corrosion

Why does a well-known RV manufacturing company insist on using dissimilar materials in the roof construction? They must be aware, like many others are, that steel staples (as well as stainless steel staples) will be subject to electrolysis when combined with aluminum sheeting. I ask this question because my RV is currently in for a roof repair and the root cause of the roof problem would appear to be caused by rotted staples that have been used to hold down the aluminum corner panels.
Barry, (Yuma, AZ)

Great question Barry. Technically what you are referring to is called “galvanic corrosion,” as opposed to electrolysis. Galvanic corrosion is basically a current flow that occurs between dissimilar metals causing primarily oxidation and rusting. There are a few things to bear in mind when thinking about galvanic corrosion. First, galvanic corrosion requires a corrosive medium in order to occur. And indeed water can act as this medium. However, if the materials are kept dry galvanic corrosion will not occur.

Secondly, in terms of corrosion-resistance, metals are often classified as active (least resistant) and inactive (most resistant). Galvanic corrosion increases the resistance of active metals and decreases the resistance of inactive metals. What this means is when a small area of inactive metal (the staples) comes into contact with a larger area of active metal (aluminum roofing), the effect of the corrosion is greatly minimized. As a result, using stainless steel staples with aluminum sheeting is acceptable given the large differential in the surface area.

Theoretically, the roof staples on an RV are not supposed to get wet and are therefore not susceptible to galvanic corrosion especially when coupled with the active/inactive properties. When galvanic corrosion does occur anywhere on an RV, the primary cause is water leaking into the affected area and it is the cause of both the galvanic corrosion and the wood damage. In your case the “rotted” staples indicates that they probably got wet before the corrosion actually started.

For the most part, I’ve got to believe that RV manufacturers understand the principles behind galvanic corrosion and adhere to somewhat strict processes designed to minimize its potential by properly sealing the area. But water intrusion is indeed an RV fact of life. Proper maintenance to roof edges, seams and moldings must be performed regularly.