Zone 1 temp issue

[Ronthecanadian]

On domestic temp controller, zone 1 (front bedroom) indicate a temp of 7-8 degrees C (50 F). Rear termostat = 23 degrees C (72-74 F). Under warranty, had dealer change termocouple in front. Problem persists? Ideas? Can this be changed to another temp sensor? Note: Dometic ac unit in front bedroom.

[jcurtis934]

Not sure of the whole picture. What I am guessing at is...you have two ac's, two thermostats, and each thermostat is showing different room temps. 50 in bedroom and 72 or so in front room. That would indicate a bad thermostat in the bedroom. IF you are talking about the outside temperature reading function on the thermostat, then I will tell you that the issue is how they mounted the sensor on the ac...under cover and in front of unit. Mine was taped in contact with the front, so it was reading coil temp instead of outside temp. John

[Ronthecanadian]

Yes there are two ac units. Both are controled by a Dometic multi zone controller. The front bedroom temp sensor is a two wire thermocouple that runs to the front right corner of the unit. I had the dealer replace the thermo the first time as it did not respond to temp changes.
They are to return and resolve. I am looking for options to suggest if this setup is just a poor design.

[kdeiss]

I can tell you the Dometic Thermostats are 3 to 4 degrees off!
My RV tech confirmed that!

[Mudchief]

Don't know if this has anything to do with it but my zone 1 is the rear and zone 2 is the front.

[Dam Worker]

My bedroom thermostat is also way off. The downstairs one is semi close but the bedroom is probably 12/15 degrees off. Shouldn't be this way but I figure I will live with it. Just got to remember when setting zone two to compensate for that. Just another annoyance that Keystone missed during their quality control inspection.

Tom Marty

[Ronthecanadian]

Yes Tom, that is our issue only the temp sensor reading in the front room is so low the ac cannot turn on. Still trying to connect with local dealer to set up appointment to resolve this problem. A new thermocouple sensor cost approx $50 Canadian, but it is still under warranty and I would like dealer to prove this setup works.

[jcurtis934]

Make sure that you don't have any of the vents pointed towards the sensor in the ceiling. If not, then I would take the little cover off and see if you feel really cold air in the ceiling that is super-cooling the sensor from its back side ( a less than stellar duct install that is putting chilled air into the attic area) When ac is running. If not, I would hold that sensor in my hand to see if it responds to body heat. Also check to see if the cream colored dense foam pad behind the electronics in sealed all around so that the cold air is not chilling down electronics, the air return area, and the attic. On mine, I have the panel in the ceiling that has the air return foam filter and electronics is easy to see with filter out. John

[chris199]

I HD the same issue. I opened up the unit from the bedroom and just manually pushed connections together on the cable to the thermostat in the corner and voila....got an accurate temp. The bad connection was right near the main unit....the lead from the a/c to the thermostat.

[Ronthecanadian]

Finally had tech on-site, replaced thermistor and removed jumper connection to electronic board. Still issue remains. Tech to order replacement electronic board. May have resolution next week? Forever the optimist.

[Ronthecanadian]

quote:Originally posted by Ronthecanadian

On domestic temp controller, zone 1 (front bedroom) indicate a temp of 7-8 degrees C (50 F). Rear termostat = 23 degrees C (72-74 F). Under warranty, had dealer change termocouple in front. Problem persists? Ideas? Can this be changed to another temp sensor? Note: Dometic ac unit in front bedroom.

UPDATE: The saga continues the tech replaced the electronic boards in both AC units, tested communication between units and thermostat. Replaced thermostat again, and re-tested the ohms readings of the remote sensor in the front bedroom unit (ok). Still the bedroom remote sensor reads 6 degrees Celsius (43 F). Tech is stumped? Sometimes it will read normal room temp, until AC starts then temp drops quickly and stays at 6 Celsius after unit is turned off?
Any thoughts?

[dieselguy]

Just for grins if you can get hold of a new cable and sensor ... just plug them in to the Dual Zone thermostat (or A/C unit whichever the connection is) in place of your existing cable/sensor to see if it reads right. I'm not talking install it ... just lay it somewhere. If it reads right ... something isn't good with the OEM cable install and or sensor.

[jcurtis934]

With the ac controller replaced, the sensor replaced, the t-stat replaced...there isn't anything else to cause the issue. The ac itself is just a dumb unit that runs or not based on getting 120vac from the controller. The controller looks at the t-stat setting to compare against sensor to know when to go on or off. Yes, the ac unit does have a delay circuit to protect it from being turned on while it still has excessive compressor pressure...but nothing else. OKAY, it sounds like to me that the only thing not changed is the actual cable that plugs into the t-stat itself and maybe that has an issue sometimes somewhwere along its wires or at either end at the connections. Chances are the it runs from the t-stat to the controller in the bedroom, then another cable to the front room ac controller. And, given that it would be a pain in the hindie to change, it was never done. BUT one could run a cable from the t-stat directly to the bedroom controller to rule this out as the culprit. While it looks like a standard rj11 telephone cable...it isn't wired the same...so the service tech would have to have one handy. All I got on the issue. John

[dieselguy]

Hummnnnn ... seems to be an echo in troubleshooting here ... Ha!

[Ronthecanadian]

Tech did try another sensor, plugged into unit same issues. Tried running new comm cable between units no change. Replaced any cable connectors, and even eliminated the short jumper cable and plugged temp sensor directly into the bedroom AC unit?
He even tried new cable from main unit to thermosat.
I can't think of anything else to replace?
Thoughts?

[Ronthecanadian]

Why would temp indicate near normal temps one moment then drop instantly to 6 degrees and stay for a few hours, before rising. As soon as bedroom unit starts temp drops even if sensor is covered to delay "seeing" change in temp?

[dhenry3]

On my first outing our 2017 3710FL, temps outside was about 95. The a/c couldn't keep, so I started checking things. I noticed our dual zone thermostat was reading real low and I couldn't get it to change. After checking a lot of things, I found a red light in the fuse panel and a reset button with it. I pressed the button and the light started flashing and the thermostat started to read correctly. Not sure what it is or does but it might be something for you to check. Hope it helps.

[jcurtis934]

Well...my last bit of advice is to drop the return air filter and look at the side of the controller. Is the room sensor actually in the right place? Starting from right it is the rj11 cable, then square power connector, then freeze sensor, then indoor temp sensor, then outdoor sensor which is under the ac cover on top of unit. Could it be as simple as freeze sensor and indoor sensor positions reversed? John

[MARK A]

quote:Originally posted by dhenry3

On my first outing our 2017 3710FL, temps outside was about 95. The a/c couldn't keep, so I started checking things. I noticed our dual zone thermostat was reading real low and I couldn't get it to change. After checking a lot of things, I found a red light in the fuse panel and a reset button with it. I pressed the button and the light started flashing and the thermostat started to read correctly. Not sure what it is or does but it might be something for you to check. Hope it helps.

Sounds like you pushed the button on your battery wizard, the T-Stat waking up was likely unrelated. Unless your Stat isn't getting good voltage as it is 12v.

Mark

[Ronthecanadian]

Jcurtis934, heading to trailer tomorrow, will check the sensor positions. I think the temp sensor is connected to the electronic board bottom left corner, but will check as I was looking over tech shoulder on roof. Thanks for the new lead.