CaptPat

The M&M website says they don’t offer tech support, that seems different than the experience several have had. Is that a new policy or a website not updated?

Thanks good to know. Yes all pass through the EMS Looking on the web I noticed that there’s a specific EMS replacement board for Monaco’s, different than that for Newmarket, etc.

Since all 3 AC are affected at about the same time it's unlikely a capacitor issue, and when running the units are blowing and cooling just fine. I think the thermostat is working fine. That leaves the EMS or the Transfer switch as possible sources (recall the situation is the same on GEN or site power). I don't think EMI from the neighbors is at fault, at home there's no one close, plus the issue was observed on the road and at a campground. Fluorescent light ballast interference is still a possibility though it's not high on my list at this time. I did poke around in the EMS box a bit and it appears to be wired as shown in the diagram above. Wires from the 120V terminal block to the breakers is a bit of a birds nest but should be traceable. I was able to get some movement on a couple terminal connections but not enough to be of concern and I wiggled most of the connections. I did not find any glaring issues the fuse was fine and the green comms light was lit. I restarted the generator and the relays clicked on when the generator started putting out voltage. AC units restarted -- no problems. I was hoping to observe a load shed event but after 1.5 hrs of uneventful run time and no shutdowns I gave up and shut everything down. I'll study your T/S suggestions of the EMS and try to get to that tomorrow. I'll also check on the roof units to eliminate any issues that might be occurring up there as well. The transfer switch is not the original IOTA and it seems to be pretty robust, a visual inspection revealed no issues, all connectors were tight. A momentary issue here may cause an interruption in power as well. Don't know how to test it however. WRT a new thermostat I think I'll go with Micro-Air, they apparently have a model that is a plug and play replacement for the 5 button. Plus it has some programming capabilities and BT connectivity. Seems to be a better alternative than trying to find an extinct 5 button in good working order.

Well looks like I spoke too soon, at the 50 minute mark all three AC units shut down, thermostat showed 1, 2, and 3 all with an underline. Resetting the thermostat did not resolve the issue, fluorescent lights were off the fuses were still installed. Bad theremostat?

I cleaned all of the RJ11 connectors there are XX of them. Two female to female in the front AC, two comms line in the mid -- they plug directly into the control box, 1 female to female in the rear and the connector on the back of the thermostat itself. All three ACs have been running fine on the generator for ~45 minutes. I did monkey around with the fluorescent lights throughout the MH and could not induce an issue. Visually the connectors seemed fine and only a very small amount of discoloration was observed on the cotton swabs soaked in 91% isopropyl alcohol. We're expecting the temps to come down below 90* in the next couple days, then I'll check out under the covers on the roof to make sure everything looks okay. At this point I'm cautiously optimistic that the issue has been corrected, I've seen these things operate for awhile and then refuse to cooperate all of a sudden. @Chuck B 2004 Windsor I'd be interested in hearing more about how you replaced the telephone flat cable with JKT, in particular how you terminated them and any issues fishing them through the ceiling.

Yes I tried all three fan speeds it didn't make a difference. I'm going to try cleaning the comms connectors today to see if that makes a difference. @Tom Cherry I always turn off the AC units at the thermostat first, then turn off the thermostat itself. I normally turn on the thermostat using the resetting procedure and always get "FF." Looks like F-F RJ11 connectors are readily available, amazon and elsewhere.

@Tom Cherry Thanks, I’ll clean the comms connections and re-try. Where did you get the spares?

I don't think it's the thermostat, temps in the coach were well above the set point and the thermostat was calling for the AC units to start.

We took our MH to a local campground for a shakedown, as it's been awhile since we've used it, in preparation for a longer trip in September. We experienced some unusual behavior from each of the 3 AC units, particulars follow-- We have 2 Dometic 630516.331, and 1 630035.331 with a DuoTherm 5-button thermostat. We ran all AC's on the generator for the 1 hour trip to the campground, set up and switchover to site power went uneventfully. Later in the afternoon units 1 and 2 stopped, though the thermostat indicated both 1 and 2 with bars under them. I reset the thermostat and AC 1 and 2 restarted they ran for another 2 hours before stopping again. Repeated the process successfully, when we went to bed I turned 1 off, leaving 2 and 3 (BR) to run through the night. In the morning 3 was still running, I assumed 2 had turned off as the set temperature was reached, thermostat showed 2 no underline, and 3 underline. As the day heated up 2 would not start when called for by the thermostat, neither would 1. I tried resetting the main power, and shifting to the generator no change. Eventually I was able to restart 1 and 2, they ran for about 90 minutes before shutting down again, shortly thereafter 3 stopped, thermostat showed 3 with underline at this time. When I reset the thermostat (several times over the day and a half and tried to start units to AC mode I could hear what sounded like a contact picking up near the inlet plenums though the units were not turning on. I'm pretty sure that site power was okay as my surge protector indicated normal V/Hz/A readings. When running each unit seemed normal, cold air and normal air flow. At no time did any of the site or coach breakers trip. Does this sound like a capacitor issue or something else? The next several days are going to be way too hot (99+) to go on the roof to see for myself. Once I get up there is there anything else I should check? Thanks