No 12-volt power when disconnected from shore power

[Rocky-in-AR]

I have a 2019 Thor Miramar and yesterday I found that when the shore power is unplugged, I cannot turn the main power (12 volt) switch on. I can turn on the inverter and it runs the refrigerator with no issues. When I turn on shore power or the generator the main power switch lights up and I have 12 volt lights. As soon as I disconnect shore power or turn off the generator the main power light goes off and I have no 12-volt power. I’m thinking the converter works since I have 12 volts when plugged into shore power. Where would you suggest to start troubleshooting? Would you think it is the main power switch itself? Thank you for any suggestions as I have not completely wrapped my head around the electrical.

[Miramar Owner]

If yours is like my 2016 Miramar, I don't think you have a converter... Just an inverter for your refrigerator and a few plugs on that side of the coach. Your lights are 12 volt and run off the battery as long as the use/store switch is in use mode. That doesn't matter when on AC from genny or power cord... The current then simply passes through.

First make sure you have it in use mode.

[Rocky-in-AR]

That’s where my problem is. The use switch won’t turn on unless I have shore/generator power applied. My model does have a separate converter/charger from the inverter. Thank you for your reply.

[Rocky-in-AR]

I probably should have said use/store instead of main power switch.

[Miramar Owner]

I stand corrected... Yes there is a converter. I've never had an issue so kind of forget about it. I recently had to replace my inverter.

[16ACE27]

Originally Posted by Rocky-in-AR

I have a 2019 Thor Miramar and yesterday I found that when the shore power is unplugged, I cannot turn the main power (12 volt) switch on. I can turn on the inverter and it runs the refrigerator with no issues. When I turn on shore power or the generator the main power switch lights up and I have 12 volt lights. As soon as I disconnect shore power or turn off the generator the main power light goes off and I have no 12-volt power. I’m thinking the converter works since I have 12 volts when plugged into shore power. Where would you suggest to start troubleshooting? Would you think it is the main power switch itself? Thank you for any suggestions as I have not completely wrapped my head around the electrical.

Your USE/STORE switch controls a battery disconnect latching relay. The control power to operate the latching relay comes from the house batteries. The inverter is connected directly to the batteries. The fact that it works says your batteries are working. So does starting the generator.

You have one of 3 possible problems:

1 - The 50 amp DC breaker in your battery compartment is tripped. Push the flag in to reset it. If you don't see the flag, trip it by pushing the button and then reset it. This is NOT the 100 amp DC breaker - that goes to your generator.

2 - The latching relay has given up and needs to be replaced.

3 - The wiring to control your latching relay has a problem. There is generally a 5 amp inline fuse for this control power at the latching relay. Make sure it is not blown.

[Travelin' Texans]

IIRC someone in the past posted that the light on the use/store switch being on indicates that your on shore power or generator not that the switch is on. So trip that switch on/off while unplugged & see if you have 12 volt power in one position or the other, the light on the switch probably won't be lit in either position.

[Rocky-in-AR]

Thank you. I will look at that tonight.

[Rocky-in-AR]

Originally Posted by Travelin' Texans

IIRC someone in the past posted that the light on the use/store switch being on indicates that your on shore power or generator not that the switch is on. So trip that switch on/off while unplugged & see if you have 12 volt power in one position or the other, the light on the switch probably won't be lit in either position.

I thought in the past the light was on when in use and no shore power but could be wrong. I’ll check that tonight also. Thank you.

[Rocky-in-AR]

Originally Posted by 16ACE27

Your USE/STORE switch controls a battery disconnect latching relay. The control power to operate the latching relay comes from the house batteries. The inverter is connected directly to the batteries. The fact that it works says your batteries are working. So does starting the generator.

You have one of 3 possible problems:

1 - The 50 amp DC breaker in your battery compartment is tripped. Push the flag in to reset it. If you don't see the flag, trip it by pushing the button and then reset it. This is NOT the 100 amp DC breaker - that goes to your generator.

2 - The latching relay has given up and needs to be replaced.

3 - The wiring to control your latching relay has a problem. There is generally a 5 amp inline fuse for this control power at the latching relay. Make sure it is not blown.

Is the latching relay typically in the Battery compartment? Would you think this is it?

[16ACE27]

Originally Posted by Rocky-in-AR

Is the latching relay typically in the Battery compartment? Would you think this is it?

That is it in the schematic but it's not normally in the battery compartment. It's normally close to the Power Center/Converter.