Forum Discussion

jurob's avatar
jurob
Explorer
Jul 09, 2015

12 volt issue shutting of my overhead AC's

1997 Gulf Stream Scenic Cruiser.

When AC's are running, If I turn on a 12 volt light it shuts the it shuts them off. I'm pretty sure it's both and maybe it might be one ac on 1 occasion (just purchased).

AC's are on a time delay so they don't start up at the same time and after they are tripped they come on at 3 minutes and all is fine unless I turn on another light and it repeats the cycle. No issue if I turn on a 110 light or microwave, etc...

Happens on shore power and gen power.

Almost makes the noise as if you raise the thermostat and you can hear the click when it shuts off.

All ideas would be appreciated! Or is this normal? Old gentleman I bought it from kept mentioning that the AC's are on time delay and its 3 minutes like clockwork.
Class A
  • enblethen's avatar
    enblethen
    Nomad
    Jul 09, 2015
    What type of 12 volt lights? Fluorescents can interfere with some types of thermostats that communicate via RF signals.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Jul 09, 2015
    Unlike home HVAC systems that have a transformer for the 24V control/thermostat system, a RV uses the house 12V... no transformer. You have a problem with your house 12V system... converter not working, weak battery, poor connections...... although it's hard to believe one bulb is enough to drop the voltage to where the Tstat cannot work, but that's what's happening.
    Is it just one particular 12V light near the Tstat or any 12V light? If you have a battery charger I'd put it on the house battery and see if this solves the problem. IF so your converter is not working and your battery has a surface charge only.
  • jurob's avatar
    jurob
    Explorer
    Jul 09, 2015
    It is not 1 particular light.

    I will check house battery voltage plugged and unplugged and let you know. I did check the coach battery and I know that has a charge plugged in, but I will check that also. I do have a solar panel or 2, but I'm pretty sure that disconnects when plugged in and not sure how that will effect unplugged and if I can bypass. Connections at the battery are clean and tight.

    The lights come on without issue and appear bright and steady.

    I appreciate the ideas and will let you know what I find out.
  • MrWizard's avatar
    MrWizard
    Moderator
    Jul 09, 2015
    Just for reference
    Our 95 Safari has roof airs and built in controls, not wall mounted thermostat

    Wondering if this is a replacement newer a/c... and the installer tapped into the lighting circuit to get power for the stat controls

    It seems like a low voltage situation where turing on the light causes the relay in the a/c unit to momentarily drop out
    It auto restarts in three minutes after the delay timer is satisfied
  • garry1p's avatar
    garry1p
    Explorer
    Jul 10, 2015
    It does sound like an sudden voltage drop.
    If you have a power distribution system there are 12V relays that control the compressors on the AC.
    If it is the overhead with internal controls many have a 12V control board, If you have wall thermostats they require 12V.

    When you say "shut off" do the units shut down or do the compressors shut down and the fans continue to run.

    The compressor has a safety device that will prevent the compressor to cycle back on (usually set from 3 to 6 minuets) to allow the compressor head pressure to drain down so that is normal.
  • jurob's avatar
    jurob
    Explorer
    Jul 10, 2015
    Shuts off like switching the thermostat to off, fan and compressor.

    I will look for a power distribution system. I think it's in the front of the engine bay.

    Coach battery is fully charged.

    Tks
  • jurob's avatar
    jurob
    Explorer
    Jul 10, 2015
    Mr. Wizard,
    Sorry, didn't see you response.

    Based on the literature I received, it looks to be original.
  • enblethen's avatar
    enblethen
    Nomad
    Jul 10, 2015
    What is the make and model of the AC unit?
    What is make and model of the thermostat?
    Have you checked the voltage level of the converter output? What is make and model of the converter?
    How old is your battery?
    Power distribution is normally inside the coach behind a panel about 12 inches square. Quite often under the refer. The 120 volt circuit breakers are similar to those in your house. The 12 volt DC fuses are behind a small metal plate adjacent to the 120 volt circuit breakers.
  • garry1p's avatar
    garry1p
    Explorer
    Jul 10, 2015
    I should have said Energy Management System that controls the compressors

    Do you have 1 or 2 thermostats? If 1 and both unit shuts down then you need to look at the thermostat for loose wires or low voltage.

    If 2 thermostats then I would look at the energy management system.

    Do check if it happens with a battery charger connected to the house batteries as it sounds like a voltage drop is causing the problem. It could be at the batteries or anywhere in the 12v system going to the thermostats or EMS.

About Motorhome Group

38,705 PostsLatest Activity: Jan 14, 2025