No 12V D/C, Converter Problem? - RV-Dreams Community Forum

DebbieM · RV-Dreams Family Member

No 12V D/C, Converter Problem?

Terry and Jo · RV-Dreams Family Member

Check the converter for fuses. Over on another forum, this discussion came up and they had a similar problem. 12V was good only to the front landing gear and maybe the fridge. Come to find out, they had replaced the battery and got sparks the first time they tried to put the cables on, and that caused their fuses to blow in their converter. They also had an inline fuse blown that was somewhere in the battery compartment.

I had a similar issue on our coach, but we only lost one leg of the 50 amp system. Come to find out, our 3000 watt inverter had a breaker trip in it. I finally found them (way back in the dark of the basement) and pushed the one that appeared to be tripped and got our power back. It was winter time and when Jo ran her blow dryer while the electric heaters were running, that breaker would trip.

Terry

bigboomer · RV-Dreams Family Member

The converter works from shore power thru a breaker. It should be a 20 amp breaker which should be labeled Conv. Check to make sure that either breaker is not tripped or that the wiring is not loose to the breaker. Check all the grounds and neutrals in the converter box to make sure they are all tight as well.

jhilley · RV-Dreams Community Member

If it works on shore power, the converter isn't the problem. Sounds like a fuse in the battery plus side.

DebbieM · RV-Dreams Family Member

Thanks for all the suggestions! The problem turned out to be one of the thermal switch/relay coming off the positive side of the battery was burned out and wouldn't reset. It would not pass 12 volt from the battery to the converter. I found this by testing the voltage from the battery through the thermal switch. It was a 50 amp thermal switch that is attached to the back wall above the batteries. I bought a thermal switch from our dealer because he recommended to carry one because they fail often.

Bill and Linda · RV-Dreams Family Member

I’m not saying this is the best price, you could look at an Auto Zone or the like, but may I recommend replacing important breakers with one of these with the appropriate rating. They can also act as a disconnect switch when necessary.

http://www.cabelas.com/product/Minn-Kota-reg-Amp-Circuit-Breaker/738084.uts?productVariantId=1202789&srccode=cii_328768002&cpncode=45-40423523-2&WT.tsrc=CSE&WT.mc_id=BingPLA&WT.z_mc_id1=00034335&rid=20

These can save you a lot of trouble in some positions.

TRAILERKING · RV-Dreams Family Member

Yes Bill.......Those are awesome circuit breakers. I use them a lot here.

rocknb · RV-Dreams Family Member

Are these Breakers something that all of us with 12v to 120 converters should have in our spare parts box ?

TRAILERKING · RV-Dreams Family Member

rocknb wrote:
Are these Breakers something that all of us with 12v to 120 converters should have in our spare parts box ?

Absolutely.......They are more expensive than a fuse. However a fuse is a "One Time" shot. Definitely best to replace the fuse with a breaker of the same size.

Barbaraok · RV-Dreams Family Member

Shouldn't it be a 120v to 12v converter? Not to nitpick, but a lot of people have inverter/converters combinations and others just straight converters.

Barb

TRAILERKING · RV-Dreams Family Member

Sorry for any "Detailed" confusion. All I am commenting on is the protection of the 12v circuits(seeing as to how the OP found the problem to be a blown 50amp fuse).
Simply stating it is way better to change up any of your 12v fuses to those 12v manual re-settable breakers. Just make sure you match amp for amp. If it has a 50amp fuse, replace with a 50amp breaker and if it has a 100amp fuse, replace it with a 100amp breaker. Simple....not hard at all.

-- Edited by TRAILERKING on Tuesday 24th of March 2015 10:38:22 AM

DebbieM · RV-Dreams Family Member

I like the resettable breakers, but the thermal switches are only $4 a piece so I now carry a few spares as recommended by the RV Tech. I'd like to hope that I won't need them often. It did take a DC Meter to diagnose, but I think that's something everyone should carry also. I did look at my friends RV power bay by the batteries and saw that their manufacturer put one thermal resettable breaker per circuit where mine is 2 for multiple circuits. To reduce the amp draw on the thermal switch, I might configure running one thermal switch per circuit. As noted in previous comments, the resettable variety are very convenient.

--Steve

TRAILERKING · RV-Dreams Family Member

DebbieM wrote:
I like the resettable breakers, but the thermal switches are only $4 a piece ........ I did look at my friends RV power bay by the batteries and saw that their manufacturer put one thermal resettable breaker per circuit where mine is 2 for multiple circuits. To reduce the amp draw on the thermal switch, I might configure running one thermal switch per circuit. As noted in previous comments, the resettable variety are very convenient.
--Steve

Not sure why they call them "thermal switches"? They are a fuse.....and when they "Pop" they're done.

A thermal switch will switch off and on with the change in temperature. Like the switches on the 110v side of a water heater.

Just keep in mind if you're modifying your circuits......The amp rating on the fuse or breaker protects the capacity of the wire it's feeding. Be sure not to have too large of an amp rating for the wire in the circuit.........Or there could be a FIRE. The 12 volt side of things can be as disasterous as 110 volt stuff. May not get a shock but things will BURN.

Bill and Linda · RV-Dreams Family Member

There are small “circuit breakers" which open when the current gets too high and a thermal switch causes them to open. When they cool down they close again. These are sometimes referred to as auto-reset and / or thermal breakers in some disciplines. They are not fuses as such but accomplish the same thing. However unlike fuses they are not a one time only device.

They are of this type:

http://www.delcity.net/store/Auto-Reset-Circuit-Breakers-!-12-volt/p_198669.h_198848.t_1.r_IF3003&mkwid=IHMeIDC4&crid=5092059113

These are extensively used in the RV industry as they are inexpensive and will usually reset themselves should a brief overload occur such as running a 12 electric jack too long or an auto-cable reel gets jammed and the motor pulls too much current – they open – then after a very short cool down period “reset.”

They work, but unlike other types of true circuit breakers you can’t use them as an on-off or disconnect switch. They will often fail with age or after several near overloads. As I commented, in more critical applications, such as feeding the output of the 120 to 12 volt converter to the battery it might be a good idea to replace these with a better quality – manually resettable breaker – such as this type:

http://www.amazon.com/MinnKota-MKR-19-Circuit-Breaker-Waterproof/dp/B001PTHKSK/ref=sr_1_2/175-5269774-4424206?ie=UTF8&qid=1427305555&sr=8-2&keywords=12+volt+circuit+breaker

As commented by Bernie (TrailerKing) be sure and replace with the same amp rating.

Bill

DebbieM · RV-Dreams Family Member

I've noticed that when I am hooking up and retracting the auto leveling jacks, the front legs seem to cause the relay or thermal switch to reset continually and I have to wait a few seconds for it to reset. When I ask my dealer about this issue they told me it was a normal protect circuit because the leveling system draws quite a bit of current, and he recommended I carry a spare because over time they will fail. So I was happy he told me I should stock one just in case, and it saved me while we were boondocking.

I am monitoring the situation and if the fuse/thermal burn out again, I'll put in the manual resettable fuses that everyone is recommending. I also plan to get a second opinion from a dealer in AZ when we bring our rig in for some warranty work and see what they recommend.

Bill and Linda · RV-Dreams Family Member

DebbieM wrote:
I've noticed that when I am hooking up and retracting the auto leveling jacks, the front legs seem to cause the relay or thermal switch to reset continually and I have to wait a few seconds for it to reset. When I ask my dealer about this issue they told me it was a normal protect circuit because the leveling system draws quite a bit of current, and he recommended I carry a spare because over time they will fail. So I was happy he told me I should stock one just in case, and it saved me while we were boondocking.
I am monitoring the situation and if the fuse/thermal burn out again, I'll put in the manual resettable fuses that everyone is recommending. I also plan to get a second opinion from a dealer in AZ when we bring our rig in for some warranty work and see what they recommend.

Yes, funny you should mention that. I almost said that in my post – that is you will sometimes hear the breaker “clicking” as they open and reset. IMO a sure sign they are very close to the overload point or are near failure.

They can get weak over time or, with lower battery voltage when under load, the circuit will draw more current (amps) to make the same power. Those amps translated into heat and “click.”

I can’t recommend putting in a larger breaker, but I could recommend either replacing those now with like type or – in my case – replace them with the breakers I recommended in my previous post as you commented.

One of the issues is a lot of RV’s have wire that is marginal in size – or have improperly crimped connectors. Both situations cause more resistance = voltage drop = higher amps = popped or clicking thermal breakers.

IF you should run into a problem getting the legs up due to these beakers tripping a lot - as a temporary band-air - plug the trailer in to 120 volts and have the batter charger / converter on. This will - should - raise the 12 volts up some. That will reduce the current necessary and perhaps keep the breaker from tripping and at least get the legs up. Naturally this won't help if the thermal breaker fails completely.

Bill