GSMBear

As an owner of the Houghton A3400, I'm not in agreement that the unit is grossly oversized for the pickup bed camper in the Joslyn Journey's video. That's a fairly large pickup camper and it has two slide outs. Their initial video is about the humidity problem and my experience shows this is solved by cycling the fan with the compressor. Shorter cycles can occur from oversized units reducing the amount of time for humidity to be removed from the air. But again, my experience shows the lion's share of the humidity problem is from the factory design of continuous cabin air flow over the wet fins allowing humidity to be reabsorbed and cycled back into the cabin. With the wiring/relay modification that I have done, I now have cabin humidity readings comparable to the interior of my home on the same property.

I am the Airstream owner you might be referring to. I'm Ho'onanea on the Airstream forum and I'm GSMBear on this forum. I've been all over the place looking for whatever information I can find on the Houghton A3400. I'm not sure I understand your reference to "relocate the room air relay from the supply air duct to the ambient area." I'm not an engineer. From what I have seen looking up into the return air duct, there is an inexpensive sensor that I believe is called a thermistor. I'm not aware of a relay being involved. Am I missing something? I would like to experiment with relocating the thermistor to an ambient area that is not in the direct flow of air coming out of the plenum. I have a perfect place for it and I even have some wire that runs from the 14" roof cutout through the aluminum ribs (think "trusses") of the roof and down the wall to a location where the original Dometic CCC2 thermostat was located. (Keep in mind, this is an Airstream rather than an Oliver.) I bought a thermistor with a longer wire that I think is the same kind that Houghton uses. I had planned to plug it into the circuit board and route it into the return air duct and test it in an ambient area. Unfortunately, it's a little misleading about how to get wires from the exposed portion of the rooftop unit into the sealed portion that can be seen by looking up from the inside when the plenum is removed. Could not find an easy way to do it and I did not want to remove the factory seal of the Styrofoam enclosed area. So I abandoned the experiment. My brother is the electrical engineer. He's not shy about using a soldering iron above his head in tight quarters. So the plan when he visits next is to snip the wire of the factory thermistor (yikes!) and he will solder a new length of wire to each snipped end allowing the factory tip of thermistor -- where the actual sensor is -- to be relocated. He says soldering the wires is important because a thermistor measures resistance and soldering the wires is the best way to minimize the addition of resistance.

RecPro Houghton Interior Fan Mod.pdf (Disclaimer -- I'm an owner of an Airstream rather than an Oliver. My Airstream came equipped with a 13.5K Dometic AC with heat pump.) I finally had a chance to document the steps for modifying the factory wiring for the Houghton/RecPro A3400 air conditioner to prevent the interior fan from running continuously. Houghton's intent for running the fan continuously is to keep interior air running across the thermistor sensor located in the return air duct for more accurate cycling of the compressor and therefore a more accurate overall interior temperature. The problem, for me, anyway, with this design is that the air being circulated is blowing across the wet cooling fins and that moisture is quickly reabsorbed into the air and returned as humidity into the living space making it uncomfortable. I'm not sure why this isn't a problem in the more hot/humid areas of Australia where the unit is manufactured. The General Manager who responded and is quoted upstream didn't seem to understand the humidity issue that I and others have experienced. This wiring modification solves the humidity problem nicely but, since interior air is not blowing across the thermistor temperature sensor continuously, there is a greater swing with interior temperatures before the compressor cycles on to cool again. Overall, I'm pleased with the change. The humidity issue was a real problem for me and I'll learn to adjust to the wider temperature swings (about 4 degrees F) with the compressor cycling. When time (and courage) permits, I might try snipping the wires of the thermistor sensor and adding an extension so that I can relocate the thermistor in an external location away from the interior of the AC unit. I still have the RJ45 "phone" cable leading from the 14" AC roof cutout area to the original location of the Dometic CCC2 thermostat that is no longer in the equation. Maybe that wire will be used to extend the tip of the thermistor to a new location. The instructions are in the attached PDF document for anyone interested.

Tummy -- are you also known as FloridaAmbient on YouTube? 🤔 If so, I appreciate the video you made about this solution. And if not, I still appreciate hearing from someone else that an additional relay to cycle the interior fan on/off with the compressor is doable. Have you seen improvements with interior humidity? I'd love to move the temperature sensor to an external location to see if that improves cycling and temperature matching between the set point and actual temperature. Once my AC runs for 90 minutes or so, then the temperatures seem to match fairly closely. Until then, it shuts off 2 or 3 degrees above the set temperature. My RV is an Airstream so I do have some space between the inner and outer aluminum skins. But there are lots of obstacles along the way even with one of those wire fishing thingies. Here is the video:

Hi all -- I have a different brand RV but have been following this thread because I'm experiencing some of the same humidity problems with the Houghton/RecPro A3400 that others here have had. I've seen a fairly recent video on YouTube from FloridaAmbient that discusses an additional relay to switch the fan on/off in tandem with the compressor cycles. He says it has made a "huge difference" with the interior humidity. His video is short and I gather that with his mod you only have one fan speed. He selected Low but it appears each speed has its own relay and a different speed could have been selected (this is my assumption, it's not stated in the video). My RV is 23' from snout to tail so maybe 19' of interior living space with no slides. The AC unit is about as center as it can be so I'm not concerned about having only the low speed. Once the interior is brought down to the set temperature, it pretty much runs at low anyway. My brother is an electrical engineer and I trust him to guide me through this process. I have the parts ordered and he will be visiting in mid July and will be staying in the RV. We plan to do this mod and document it will with pictures and narrative and I'll turn it into a PDF. Stay tuned. I hope it's okay with the forum guidelines to post an external link! Here is the video: