Continuing saga rear AC Dutch Star..need help

[Magredvet]

It's a CCC2 thermostat, which is the latest version.
Got Brooks Wagner coming out next week. I'll keep y'all informed, in cae it helps someone in the future !

[Quincy]

Are your other AC units running when this is happening? If so shut them both off and allow a little time for the ducts to read close to ambient temp then only turn on the problem unit and let us know what happens please.

Good Luck-Q

[Magredvet]

It's usually difficult to do that, as after any length of time, after messing with the connections the room inside temperature is reading 45 deg or some such, so it is not possible to get the AC to run at all.
E.G. last Saturday I unplugged/reconnected the data lines to unit 3. Inside temp immediately reads 74 deg (pretty close to correct) I set the AC to 73 (no other units running), and after a while it cycles on, as it should, pulls the temp down to 73, then cycles off. ten minutes later it is reading 71 deg inside. Ten minutes after that 43 deg.
Since then it has dropped to 32 deg, and that's where it has stayed since then. Other units cycle perfectly, and inside temp shows correctly (give or take)
If I was to unplug the connectors again, then it would go back to a correct reading........then drop off as has been usual, since the unit was changed.
Immediately after the unit was changed, if the thermostat was reset, then it would read correctly for a couple of days (many cycles) then drop off again.
AC board, Thermistor harness, thermistor, and thermostat have all been changed without any significant improvement ??????
Another guy on here has had a similar experience, except his just started doing this one night, whereas mine started after a unit swap.

[rvbiker45]

I've been reading this linked discussion and I can feel your frustration.
Short story. After many futile attempts at finding an answer to an electrical problem. I got a copy of the electrical schematic from Spartan. I traced the wiring to the area of commonality which was a relay. Bench testing showed that it was working sometimes and sometimes not. Replaced the relay, on a trip now with over 300 miles logged, and so far have not had the original problem show up.
Suggestion, look for relay(s) that control the operation of the a/c's. If found, replace them all, very cheap.

["007"]

I guess a call to BrooksW top Newmar MOBIL TECH is needed, home is in Texas but he travels the mid-west.

[Magredvet]

Originally Posted by "007"

I guess a call to BrooksW top Newmar MOBIL TECH is needed, home is in Texas but he travels the mid-west.

Finally got a hold of him today, and he is coming out Tuesday. I hope he can find the root of this problem.

["007"]

I think he will and its probably your new AC.

[Quincy]

Originally Posted by rvbiker45

I've been reading this linked discussion and I can feel your frustration.
Short story. After many futile attempts at finding an answer to an electrical problem. I got a copy of the electrical schematic from Spartan. I traced the wiring to the area of commonality which was a relay. Bench testing showed that it was working sometimes and sometimes not. Replaced the relay, on a trip now with over 300 miles logged, and so far have not had the original problem show up.
Suggestion, look for relay(s) that control the operation of the a/c's. If found, replace them all, very cheap.

That would be the contactor for the compressor and as a last resort might be worth a try. One at a time though so you might not have to buy all three.

[Quincy]

Originally Posted by Magredvet

Thanks for the replies gents, I'll try to address the questions.
The rear AC was always zone 3, as it worked well for 18 months until replacement, and the dip switch is set to zone 3. The installer changed out the board, and gave me the old one, which was also set to zone 3.
The six pin plug that connects to P6 goes to a box on the coach, and has a red and black wire, so I'll check that for 12v.
007, I have looked at the diagrams, and all I can find are generic installations where the last AC has only one comm cable. Cloud dancer, would you like to share how you achieved this in more detail ?
The thing that puzzles me is that disconnecting, then reconnecting the comm cables causes it to read correctly for a couple of cycles, then gradually the indicated inside temp falls off, til it hits 32deg F
It has these cheap telephone connection blocks, from the coach wiring to the AC harness. basically the only thing that hasn't been changed is these short runs of Telco cable, that came with the unit.
Does anyone know if you need to take the board out to get to the Telco connectors at the board, as I may try and bypass these two cables.
My next plan is to see if there's 12v, then disconnect the existing comm cables, and plug a thermostat directly into the board comm socket, and see how that works, and run it as a stand alone unit. The only down side of this (if it works) would be trying to route the new cable to the bedroom, and pulling the cable inside the wall to mount the thermostat
Thanks again for all the help, it's not so much of an issue now, but come March or so, I'll be needing it to work !

It is hard to visualize what might be happening from a description without being there. Does a three zone system have three independent sets of ductwork? I keep coming back to either the sensors are not working properly (but they have been replaced) or the sensors are in the wrong duct. Or more than one AC feeds a particular duct and the other AC is affecting the sensors for the new AC.

I know this is a suggestion with some holes in it but the temp over the evap. coil should be about 40 degrees and can get colder if the filter is restricted. The sensors might be fine but getting wrong input. ie; cold air.

Maybe worth a shot...Q

[bruceisla]

Originally Posted by Quincy

It is hard to visualize what might be happening from a description without being there. Does a three zone system have three independent sets of ductwork? I keep coming back to either the sensors are not working properly (but they have been replaced) or the sensors are in the wrong duct. Or more than one AC feeds a particular duct and the other AC is affecting the sensors for the new AC.

I know this is a suggestion with some holes in it but the temp over the evap. coil should be about 40 degrees and can get colder if the filter is restricted. The sensors might be fine but getting wrong input. ie; cold air.

Maybe worth a shot...Q

You might want to read from the beginning. The rear A/C worked fine until the remote temp sensor started reading wrong. And it still works if the comm cables are reseated ....
The remote sensor is wall mounted in a room.

["007"]

There was a spell where the remote sensors fell down into the wall cavity and naturally you would get crazy readings.
There is a fix someplace if I can find it. ----- This can possibly be your answer.

[Magredvet]

Room sensor is still where it should be. One guy suspected it was bad, so he passed a brand new thermistor down through the duct into the bedroom. Again this worked for one cycle, then temp went wild again, so I'm convinced it's not the sensor

[Quincy]

Originally Posted by bruceisla

You might want to read from the beginning. The rear A/C worked fine until the remote temp sensor started reading wrong. And it still works if the comm cables are reseated ....
The remote sensor is wall mounted in a room.

I dont get the attitude but I did spend some time re reading the posts from OP.

First I have repaired many compressor wires without condemning the whole unit. Just because a wire is burnt through does not necessarily mean the whole unit is trash.

Since you have a new unit then what you are describing has some feeling of a bad anticipator. (now remember I am old and things have changed over the years) but the anticipator anticipates the room temp and keeps the unit from short cycling. Short cycling could be a reason for a burnt wire at the compressor. As I said before these things are only suggestions as not being there is a hindrance but might be worth looking into. Anticipators use to be resistors in T-Stats but could be located anywhere it can influence the Stat.

Good Luck -Q

[bruceisla]

Originally Posted by Quincy

I dont get the attitude but I did spend some time re reading the posts from OP.

Good Luck -Q

No attitude .... it just sounded like you hadn't started from the beginning.