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Old 12-08-2014, 11:10 PM   #1
1 Rivet Member
1975 31' Sovereign
Poulsbo , Washington
Join Date: Dec 2014
Posts: 5
12v interior lights not working: replace Univolt?

We've just been gifted a 75 Sovereign to use as an office/music studio and extra living space on our farm. (Can you believe it?? Wow, do we feel fortunate!)

We are new to the forum and have tons of questions. It looks pretty great overall, but needs systems to be working. We brought it home and hooked it up to 110 shore power, but have not yet bought a battery. I've flipped the breakers off and back on. The outlets work but not the lights. I've tested the fuses and they're fine. There doesn't seem to be any life in the Univolt. No humming, etc.

I've read that newer converters are better and am wondering if I should just bite the bullet and replace the Univolt or is it worth it to troubleshoot? If replacing turns out to be the way to go can anyone recommend brands and models? Do I need to get one rated for 30 amps or is it better to go higher for some reason?

Thanks in advance for the help. I've spent some time perusing the forum and am empressed with the knowledge, enthusiasm and politeness.


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Old 12-08-2014, 11:22 PM   #2
Rivet Master

2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 2,258
Quick basic troubleshooting:

Obtain an inexpensive digital voltmeter and check the voltage on the output of the Univolt with shore power on. it should be 12-14 volts DC. If not, check the following

Verify the battery leads are not shorted together or to the trailer chassis--that will absolutely stop everything 12 volt.

Verify the Univolt is getting 110 volt AC power at the breaker and at its input side.

If there is power into the Univolt, and nothing is coming out, and there are no 12V shorts or blown fuses, its time for a Univolt replacement with a better Convertor.

Consider temporarily installing a charged 12V battery as a test. Be careful hooking it up with the right polarity.

Search other threads for replacement data and more troubleshooting information... Look for 'Convertor replacement" as an example.

'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Radios inside and many antennae sprouting from roof, ProPride hitch
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Old 12-09-2014, 05:49 AM   #3
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jdalrymple's Avatar

2009 27' FB Flying Cloud
1991 35' Airstream 350
Siloam Springs , Arkansas
Join Date: Oct 2006
Posts: 1,490
If it turns out the convertor is bad, don't confuse the current rating of the trailer and that of the convertor..

The trailer itself is probably rated for a maximum of 30 amps 120 volt input. This allows enough to operate the 120 volt appliances installed like the air conditioner, the heating element of the 'fridge, any AC lighting that may installed, etc. As well as the 120 volt AC current needed by the convertor to make 12 volts.

The rated output of the convertor is the amount said convertor makes at 12 volts DC. This current is used to power the DC appliances like most of the lighting, vent fans, control boards of the 'fridge and water heater, the furnace, charge the batteries, etc.

45-60 amps of 12 volt DC power seems to cover that for most trailers.


Jeff & Cindy
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'09 27FB Flying Cloud
'91 350 LE MH
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