Long Battle with AC/Furnace/Heat Pump Issues

[burgess001]

I think we finally (after 4 years) resolved our aforementioned issue. Our furnace worked great when it was above about 40 degrees, but not when it got really cold. The AC was unpredictable in the summertime. I thought it must be the control board, but three different shops were reluctant to change it. I was getting frustrated. Finally one said that, even it it was the control board, if something burned out the old one, it would likely burn out the new one. OK, so what do we do. After spending nearly $2,000 on troubleshooting, thermostat, etc, in three shops, the last shop finally said that the only thing to do was start rewiring the system until something helped it. So he began hanging wires from connector to connector. Finally, he wired around a short, jumper wire in the REAR AC and BINGO. Things started working. So, it cost about $2,000 to replace a short phone line in the rear AC. Oh, the joys of RV ownership. Just hope it is really fixed now

[crasster]

I can't even tell you how many people I've seen switch to space heaters in their coaches after problems ensued. Somehow A/C never seems to have as much trouble as heat.

[burgess001]

Doug Rainer... Sounds like if it happens again, I need to make a trip to Carrolton. Thanks for the info.

[dougrainer]

burgess001 wrote:
I'm old school too. I was convinced it was the main board that drives both AC's, both Heat Pumps, and the Furnace. Reason was, when it got cold enough to kick the heat pumps over to furnace, nothing worked. That was just too much of a coincidence. I'm guessing the wire was keeping the rear heat pump (which was not on) from telling the furnace it could come on. Its too much for me. I can't do anything but air the tires any more.

1. There is NO main board that controls all those functions
2. That "phone wire" is a communication cable that links the front AC to the Rear AC and the wall tstat. There is a "Phone" cable from the wall tstat to the front AC. There is a "Phone" cable from the front AC to the Rear AC
3. The wall tstat on your Dometic system DOES communicate with BOTH Roof AC Module boards. But the tstat ONLY sees what the Roof AC boards tell it to see.
4. When the outside Ambient temp gets too cold for the HP to produce heat (below 35 degrees), on EACH HP, there is an outside ambient temp thermistor and when it senses below 35 degrees, the Control board for THAT HP will stop the compressor and activate the furnace automatically. IF you have just 1 furnace, then the Rear HP will just stop running and the front HP (which the furnace is wired to) will activate the furnace as long as the front HP has also sensed that 35 degree ambient temp. If you have 2 furnaces, then the rear furnace will be activated by the rear HP and the front furnace will be activated by the front HP
5. Regardless, when you have such a intermittent problem as this, you need to have the Service Technician be aware of all the previous repairs that have not fixed the problem. Doug

[burgess001]

I'm old school too. I was convinced it was the main board that drives both AC's, both Heat Pumps, and the Furnace. Reason was, when it got cold enough to kick the heat pumps over to furnace, nothing worked. That was just too much of a coincidence. I'm guessing the wire was keeping the rear heat pump (which was not on) from telling the furnace it could come on. Its too much for me. I can't do anything but air the tires any more.

[FIRE_UP]

This gang, is the problem with modernization. While we all know how much better todays engines are, 'cause we don't have to change "POINTS, ROTOR, AND CAP" in the distributor, analyzing a problem with todays engines, is considerably harder than it was with a carbureted, points and condenser engine.

The same goes for our appliances in our coaches. The more intricate they make them, for specialized operations, i.e. heat, dual zones, A/C one or two zone's and more, the more complicated the systems are and, along with that is, the harder it is to analyze issues if and when they crop up.

I think many technicians really do give it a good effort but, things are so complicated that, even when properly schooled in many of todays RV appliances, (and just how many actually go to school on RV appliances) it's still seriously difficult to go "right to the answer" in some or, many cases.

It's too bad that, todays appliances couldn't have a computer plug, just like the ones on todays cars and trucks, to plug into to see what's happening with the appliance and, to see what, if any are causes of issues within appliances. That would be cool.

Anyway, glad the OP got his issue resolved and, hopefully it's done for quite some time and he gets good usage out of his A/C and Heat Pump.
Scott

[old_guy]

dinosaur boards are far more superior than OEM boards and cheaper. I can not help but wonder why they don't put them in the units in the first place. these things have been around for years, yet the industry has not gotten the message yet.

[wa8yxm]

Glad you found your problem, But I will say this:

I have an atwood "Hydroflame" furnace (no heat pump).. The OEM control board uses a single wire for both high voltage ignition and flame sense,, Efficient design but... What happens if the change over from MAKE SPARKS, to SENSE FLAME, goes wonkey and you hit that flame sensor chip with around 1,000 volts...or more? (NOthing good I can assure you).. I believe that is what killed my board.

I replaced it with a Dinosaur board... They are highly recommended by others so I got one from American RV in California, Less than half the price of the OEM board it was.

I am a trained Electronics technician

First thing that struck me when I opened the box was the QUALITY of this puppy, makes the OEM look like junk (Well the oem was junk at this point)..

Then as I looked it over more closely there on the board is a device (Gas Discharge Tube) that is one of the devices used to clip voltage spikes on electric circuits... Right next to the flame sensor chip. Wonder why that's there? (NO I DO NOT, I know why it is there).

RV purchased Spring 2005
Board replaced 1st of 2012 (Failed in fall 2011)
Expect to replace it again... Actually, I do not expect to replace it again.

[rgatijnet1]

Congrats to the shop that finally troubleshot the problem the correct way. All of the other places had poor technicians that just threw YOUR money at the problem hoping that they could find the problem.