How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Randall Your Own Question
Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 10488
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
21664427
Type Your RV Question Here...
Randall is online now
A new question is answered every 9 seconds

When the air conditioner is running in my motorhome and I

Customer Question

When the air conditioner is running in my motorhome and I turn on an overhead light (12 volt) the air conditioner turns off. It will come bak on in about 3 minutes. What would be causing this? bad thermostat?
Submitted: 6 months ago.
Category: RV
Expert:  Randall replied 6 months ago.

Hi! My name is ***** ***** I can assist you with this. I may need some additional information from you first in order to give a complete answer.

Customer: replied 6 months ago.
ok
Expert:  Randall replied 6 months ago.

This may be a battery issue. That would be the first place to check and the battery cable connections. Be sure they are clean and free of corrosion.

Customer: replied 6 months ago.
i have done that and performed a dead load test on the batteries
Expert:  Randall replied 6 months ago.

If the batteries are over 3 years old, they may be failing. If you check the converter or inverter/charger you can see if that may be the issue. A small digital multimeter is good for this. Be sure you check the ground lead to the batteries. If all that checks out, then maybe the thermostat may be the issue. Let me know the make and model.

Customer: replied 6 months ago.
batteries are less than 1 old, I completely removed the inverter/charger and the a/c would still go off when I turned on a light. I have a 1998 winnebago adventurer
Expert:  Randall replied 6 months ago.

Is the light fluorescent style? IF so, it may be giving some feedback. If not, and there is no AC ripple out of the charging system, then the thermostat or the connections are suspect.

Customer: replied 6 months ago.
I do not believe there is an AC ripple because I completely removed the inverter/charger. It is not a fluorescent light. I disconnected the motor home AC going to the A/C unit and ran a AC line directly from an outlet at the house and the same problem occurs.
Expert:  Randall replied 6 months ago.

Then the thermostat or control module would be suspect.

Expert:  Randall replied 6 months ago.

What is the make and version of the thermostat?

Customer: replied 6 months ago.
Coleman - Mach
Expert:  Randall replied 6 months ago.

Check the fuse after you remove the cover. See if that is bad or the fuse holder has some corrosion. See what the voltage is on the fuse.

Customer: replied 6 months ago.
13 volts. When I connect the volt meter to the leads going to the A/C unit from the thermostat I get 13.08 volts, when I turn on a light the volts drop to 0.14
Customer: replied 6 months ago.
Then after about three minutes the A/C comes back on.
Expert:  Randall replied 6 months ago.

What is the voltage AT the batteries? If good there, follow it to the circuit that has dropped. It maybe a shortstop breaker is failing. Those will open up under heat and then close back up when they cool off. If the light has a short that can do this. I am attaching a photo of a shortstop breaker so yo know what they look like. Usually in the battery control center. https://www.bing.com/images/search?q=shortstop+breaker+photo&id=FF1DB9A9E4D0D1A7540EECAAC90C3BA5FC88C3D3&FORM=IQFRBA

Expert:  Randall replied 6 months ago.

An auto breaker won't have the black button on it.

Expert:  Randall replied 6 months ago.

What is the actual model number of your RV? Let me grab some wiring diagrams.

Customer: replied 6 months ago.
1998 35WP
Customer: replied 6 months ago.
Volts at the batteries 13.25
Expert:  Randall replied 6 months ago.

Is that with the light on? If so, then the problem is on that circuit and it must control the AC thermostat as well. See the attached wiring diagrams. http://www.winnebagoind.com/diagram/1998/126757.pdf

Customer: replied 6 months ago.
the light is on
Expert:  Randall replied 6 months ago.

If those share a common connection on the hot lead OR the ground it may be loose or have some corrosion. You can add a "test ground" to that circuit to test that theory. Use a length of wire with an alligator clip on each end.

Customer: replied 6 months ago.
I just disconneted the 12 volt lead at the House 12 volt circuit breaker and connected the lead to a jumper wire coming directly from the batteries and when i turn on a light the A/C continues to run.
Customer: replied 6 months ago.
I disconnected the lead going to the A/C at the circuit breaker
Expert:  Randall replied 6 months ago.

Sounds like you are getting closer to the source of the problem. So, it appears to be on the positive side and not the ground.

Customer: replied 6 months ago.
Any suggestions on where to look?
Customer: replied 6 months ago.
Could the curcuit breaker panel be bad?
Expert:  Randall replied 6 months ago.

Try to see if you can find the junction of that light circuit and the AC. Look at the diagrams and see if those are sharing a feed. Sometimes you can pull out the light and see that. And yes, that is possible. Bypass it and see if everything works.