AC Thermostat & LPG/CO2 Alarm Questions

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RVJeeper18

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Sep 19, 2018
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12
Spent the long holiday weekend camping and had issues with both our AC and the LPG/CO2 Alarm. Hoping someone has seen similar and might have simple solutions or Ideas. Motor Home is a 2017 32' Class C Leprechaun with single roof mount AC and "Domestic" brand Thermostat. We have owned the rig for 18 months and taken many trips with out these issues.

AC - Had the following problem only at night: AC working fine, blowing cold, cycling fine during the day (although it was hot during the day so it ran a lot but did cycle occasionally). At night around 1-2 am we would wake up and it would be hot and the AC was cycled off. I would get up and drop the set temp on the thermostat and go back to bed, but it would not cycle back on. If I turned everything off for a few minutes it would work fine when I turned it back on, but a couple hours later same thing - wake up and hot in the RV and AC cycled off. Rinse repeat.
Seems like a thermostat issue - is that a good guess? Any way to test a thermostat to see if it is not reading ambient temp correctly or not signaling AC to cycle? Looks like it reads initial ambient temp correctly and cycles AC on and off for a few hours, but at some point cycles off and will not cycle back on when it hits set temp? How hard to replace a thermostat - that is one home repair I have never messed with? Any difference between a RV thermostat and regular home setup?

LPG/CO2 Alarm - Again problem almost exclusively at night: Around 1-2 am (yes we lost a little sleep that night..) the LPG Alarm went off (different tone and blinking light for C02 vs LPG alarm) - I could Mute it but it still showed LPG detected and would go off again every 8 Minutes. The sites are full hookups so we (nor any other campers) were not running generator or using LPG. Had to open windows and vents to get alarm to stop. I checked and our LPG system was closed off at the tank - no smell of gas at all. Aired everything out good (and messed with AC while waiting), closed everything back up and went back to bed. Hour later it all happened again same procedure & result. This time i went searching for any other source of gas and found that we had several of the little green disposable 16.4 oz. propane cylinders stored in outside compartment across hall and directly below alarm. They were new, unused, with little plastic caps still in place but I pulled them out anyway and put them 50'+ away and down wind. I also had one of the cylinders installed on a small grill about 20' away so removed it and put with the others. By this time we were exhausted so just left the windows/vents open and cranked the AC all the way down and went back to bed. No more issues over the rest of the night. During the next day we had all the windows/vents closed back up, little cylinders still stored away and down wind, and had 2 more instances where the LPG alarm went off. Both times I could get it to reset without venting. Following night no problems.

I know the alarms are set to go off on very low concentrations, I assume lower than you can smell gas? Could the little cylinders be the culprit? Could the valve on the LPG tank not be closing completely and I have a leak somewhere in the system? The LPG tank itself is located under the motor home as far forward and away from "house" and alarm as possible - guess it is possible the relief valve could be leaking slightly or venting (although tank was only 3/4 full and I would expect any pressure venting to happen during the heat of the day)? Could the alarm be bad?

I am guessing it was the little cylinders - just curious if anyone else has had similar issues and found other solutions?

Any chance the 2 issues are related since they happened the same night?

Any info/advice appreciated. Would really like to be able to remedy these situations and make repairs myself rather than dealing with the HORRIBLE RV dealer service departments.
 

Rene T

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May 20, 2011
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19,479
Location
Farmington NH
Both the thermostat and detector require 12 Volt DC to operate. I'd be checking the voltage at the battery and also checking the output of the converter. The way to do this is to disconnect from shore power, disconnect the negative battery cable and check the voltage of the battery. You should be getting at least 12.6 volts. Then plug back into shore power, check the voltage at the disconnected battery cable and to the still connected positive cable. You should be reading around 13.6 Volts DC
 

RVJeeper18

Member
Joined
Sep 19, 2018
Posts
12
Rene T said:
Both the thermostat and detector require 12 Volt DC to operate. I'd be checking the voltage at the battery and also checking the output of the converter. The way to do this is to disconnect from shore power, disconnect the negative battery cable and check the voltage of the battery. You should be getting at least 12.6 volts. Then plug back into shore power, check the voltage at the disconnected battery cable and to the still connected positive cable. You should be reading around 13.6 Volts DC

I have dual house batteries - what is procedure for that?  Disconnect neg cable from "downstream" battery (how do I know what order they are in)?  Test both batteries for voltage separately?  When reconnected to shore power test positive cable on "upstream" battery and disconnected neg battery cable on "downstream" battery?

Thanks for the help.
 

Rene T

Site Team
Joined
May 20, 2011
Posts
19,479
Location
Farmington NH
After disconnecting the negative cable from the battery, then disconnect the negative cable between both batteries. Then you can check the voltage of each battery separately.
 

Henry J Fate

Well-known member
Joined
Jun 14, 2018
Posts
1,979
The a/c unit probably provides its own low DC voltage for the control thermostat. Check the installation instructions to be sure. If that is true for your a/c unit, the problem would be confined to the unit/thermostat.
 

grashley

Well-known member
Joined
May 7, 2015
Posts
6,591
Location
Western Kentucky
I must agree with Rene, but one other possibility is a pet that "outgassed" near the detector.  That will also trip the alarm.
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
76,136
Location
West Palm Beach, FL
If the thermostat is shared with the furnace, the source power for the t-stat may be independent of the a/c unit.  Either from the furnace or direct from the 12v bus (fuse box).

An RV thermostat is pretty simple in concept - it monitors ambient  and puts +12v on a wire to the a/c when the set temperature is exceeded.  Usually ambient is measured right at the thermostat, but multi-zone models often have remote sensors. If the t-stat serves both furnace and a/c, it does the same except the threshold for heat is the opposite - ambient less than set.  With an appropriate Set temperature, you can test the output (control) wire for +12v to see if it is working.  You can also check the +12v input to the thermostat to make sure it has power to operate with.  Also, you can jumper from the +12v input to the output wire, bypassing the thermostat ambient measurement altogether.

Swapping in a new thermostat of the same type is a piece of cake - just disconnect and reconnect the wires. Take careful notes and a picture or two before disconnecting anything, though.
 

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