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The most likely cause here is they didn't set the dip switches on the air conditioners correctly.if you remove the panel on the control boards in the air conditioners, the small square plate that covers the 110v connections. inside you should see a series of dip switches.the front ac should be number 1 and controls the rear ac too.you have to set the dip switches correctly, depending on the set up you have. they are marked, but it is hard to see, will need a flashlight and probably step stool to get in there. have to set the switch for furnace, on the front ac, which i believe is number 5 dip switch. and switch 1 for heat strip. and on the rear, set the dip switch to tell it, it is zone 2, which i believe is switch 2. if you have a rear furnace, turn that on as well. and also switch 1 for heat strip if that has a heat strip too all other switches should be off.then do a reset on the thermostat and it should recognize this new settings and display accordingly.try that first. it is a common error often over looked, since dometic ship their control boards with all switches set to off. if you have any problems figuring out the configuration of switches, let me know and i can try and put together or find a diagram that shows them.
We have been partially successful. We have the #1 unit working as it should with all three modes functioning as they should. we have been able to now see the #2 unit and have reprogrammed the controller for it.However we can not get any of the modes to respond. We have checked all connections and found one that is wrong. According to our wiring diagram the power connection to the board should go to K6 com. When the mechanic at family RV put in the new boards the power was sent to K1 and the connection to K6 shows the connection that should have gone to K1. They were switched. We would assume that this is the problem, however we would like to know if you agree with our findings before we make the change.
sorry for the slow reply.I'm not sure I'm following with the k6 and k1. are you referring to the relays? he should not have messed with those at all. that is all wired by dometic when built. he just adds the 110v wires and hooks up data cables.. the relays have 110v going to them.unless I'm missing your point.the only wiring that should have been required is, connecting 110v wires to both control boards. connecting 12v power and ground to the front control board.(rear ac is fed from the front via the data cable) and plugging in the data cables. the one from the thermostat goes to the front ac, then a cable runs from the front ac to the rear ac. it doesn't matter which plug they plug into. if all the dipswitches are correct, that should be it. just so I'm clear. the front air conditioner (zone 1) is working fine in all modes. the rear though, zone 2, is being detected by the thermostat, but not doing anything? can you hear the control board click when you select cool or fan? or is there nothing at all?i wouldn't mess with any internal connections in the control board.if the thermostat is seeing the second ac and showing the correct modes, I would verify you have 110v to the second AC. do you have a selector switch to switch between the ACs?
We finally figured out what the problem was. We checked all of the connections to the circuit board for the #2 conditioner. We found that when the mechanic that swapped out the board he put the the connection to K-6 to K1 and visa-versa. This solved the problem when we reversed them.When changing these boards you have to remove the spade connectors that go to the board. When he put them on the new board he made an oops.Thank you for your help.