A/C Fan Runs Continuously
Dear RV Doctor:
We have a 1998 motorhome with an Airxcel air conditioner and a Coleman-Mach thermostat. The thermostat controls — low, high, and automatic fan — work fine. We are able to turn the unit off with the thermostat. The system cools and heats fine. Our problem is the unit will not turn off by itself no matter what temperature we set. What is the problem?
Ethel Cameron
Via email
A lot depends on the ambient temperature range you are experiencing. It’s not unusual for a thermostat to keep the fan running until the temperature is a few degrees below the actual set point of the thermostat. And with the thermostat fan mode set to “on,” the fan will indeed run continuously. Only in the “auto” mode will it shut down eventually.
Here’s what’s likely happening: You set the thermostat to your desired temperature. Once the motorhome is cooled to that degree, the compressor shuts off, but the fan continues to run. This helps disperse the cool air throughout the coach and helps cool off the compressor. The thermostat then must sense that the temperature is a few degrees below that set point before it shuts down the fan. If the ambient temperature is such that the inside air cannot reach a few degrees below the set point, the compressor kicks in again. In many locations, the fan will run continuously with the compressor kicking in only when needed.
If it does become annoying, you can continue to simply switch off the thermostat manually. I’m guessing after a few hours, though, you won’t even notice the fan blowing. I doubt anything is really amiss, but a good service tech will be able to verify that.
Better Battery Charging
Dear RV Doctor:
I’m thinking about buying a Xantrex 60-amp TRUECharge2 battery charger for my coach. I have about 500 watts of solar panels feeding three Lifeline AGM batteries. In the winter months, I don’t seem to get enough sunshine to fully charge them before night catches up with me. And if I run the generator, it is lackluster in bringing the batteries up. If I bought the Xantrex charger and powered it off of the generator, would that do the trick? I’m thinking that I may have to stop the generator from doing any charging while the Xantrex is doing its thing. What are your thoughts? And, lastly, how do I stop the generator from charging my batteries, since it won’t charge them correctly in the first place?
John Rott
Via email
The generator itself does not charge the batteries. It simply provides the 120-volt AC electricity to power the onboard charger, be it a converter or an inverter.
Adding the TRUECharge2 is a great idea, as it will charge the engine-start battery at the same time. The TC2 is equipped with three charging outputs. I recommend configuring it in parallel with your existing battery charge line. Because of the inherent electronics, the batteries usually dictate which charger to use. And because of its sophistication, the TC2 typically will become the dominant charging device.
DC voltage always flows from the highest to the lowest, so if the batteries hold a lower voltage, either charging device will be effective at bulk charging, though the TC2 at 60 amps far exceeds the common charging converter. And, more importantly, as the battery bank comes close to full charge, the TC2 automatically will determine the amount of charging current based on the total capacity of the battery bank, the electrolyte temperature, and the state of charge of the bank.
It makes sense to upgrade. The TC2 will never overcharge the battery bank; the stock converter very likely could.
Accessing A Holding Tank
Dear RV Doctor:
I have a 1994 Holiday Rambler. It is a Cummins diesel pusher on an Oshkosh chassis. It is my first RV, and I have a few minor issues I want to tackle. For one, the ACC circuit has no power. I have checked and replaced the column switch and tested the fuses. I assume there must be a relay of some sort that is bad. I also needed to replace my holding tank sensor board and tank sensors. I purchased the iSeries system and now find that I must remove the black-water tank to gain access to the sensor for the gray-water tank. How difficult is it to remove the black-water tank?
Gerald Gindlesperger
Via email
My focus is the house portion of motorhomes, so it’s best to visit FMCA’s online Forums (community.fmca.com) regarding the dash or ignition system. But first check all the fuses in the dash fuse panel. If I’m not mistaken, all dash electrical is protected through that chassis fuse panel and likely was installed by the chassis builder. Also, if accessories that normally operate only with the ignition on (such as the HVAC fan) are not working, the ignition solenoid may be the problem. A signal from the ignition switch acts to close the solenoid so that all the high-amp accessories do not have to be powered through the ignition switch itself.
As for the holding tanks, code requires that all of them be removable. Of course, you might have to half-disassemble the coach to get to them! It was quite common for some builders to install both holding tanks together, right next to each other or one on top of the other. So, it’s quite possible one tank will have to be removed in order to gain access to the other tank. Not a very good design, in my opinion, but it’s totally code compliant.
Obviously, if you choose to perform this task yourself, dump and flush both holding tanks and then look for how that black-water tank is secured in place. The toilet connection (and any other drain connection), the outlet assembly, as well as the vent stack for that tank will have to be removed in order to get the tank out. It’s on the more difficult scale, and most RVers usually would leave this task to a professional technician. But if you have the correct tools and wherewithal to take your time, it’s not really rocket science. It just takes careful planning and execution.
Air Bubbles From Water Pump
Dear RV Doctor:
My motorhome has a SHURflo 4008 water pump that discharges air bubbles from an 8-foot PEX line that I’m using to test it. There is very weak water pressure at all the faucets in the coach. It seems all I get is low pressure and lots of air. What’s going on?
Charly Barnes
Via Email
It’s sucking air from somewhere. I’m thinking the bypass flow-metering device on the pump is out of adjustment. This assumes the check valve on the inlet fitting is good and viable. Be sure all the nonpressurized components are tight (between the tank and the pump), including the filter/strainer. If possible, look for bubbles by observing the strainer on the water pump — the problem might be the strainer gasket, or it could be between the tank and strainer.
Of course, a downstream installation of an accumulator may help some, too. Without actually seeing, hearing, and measuring voltages and current flow, these are my best guesses.