Help! Electrical not working on 12V

[July]

Hi everyone,

We need help! My husband went to get our dear Airstream last Sunday from the parking where we keep it during the winter. However he couldn't get it on the road, there seems to be a problem with our electrical system.

All electrical works fine on 110V, but nothing works on 12V. Not even the slightest flicker of light.

The batteries are brand new and fully charged, my husband tested them.

What should we check? Is there a fuse somewhere that might need to be replaced? A wire?

We need to leave Friday for the long week-end!

Thanks in advance,

Julie and Francis
Airstream Sovereign 1986

[SilverHouseDreams]

How long was it stored for? Was it plugged in the entire time it was stored? How did he "test" the batteries?

There are several fuses/breakers involved in powering most trailers, the simple path is to trace the voltage back from battery to device. So check the cables on the batteries, clean the terminals if necessary. Then go to the power center where the breakers/fuses are, check the voltage there. If there is no voltage at the power center, then the breaker/fuse that is between the battery and the power center is the issue (or it is switched to "store" mode). There should also be 12V power at the power center when plugged in to 110V.

[uncle_bob]

Hi

Do you have a battery disconnect switch? If so, did it get turned "on" when you came out of storage? If not a disconnect, did the negative lead to the battery get pulled and not re-connected?

Bob

[A W Warn]

Originally Posted by uncle_bob

Hi

Do you have a battery disconnect switch? If so, did it get turned "on" when you came out of storage? If not a disconnect, did the negative lead to the battery get pulled and not re-connected?

Bob

^^^ this is most likely what is wrong ^^^

If not, look to see if there is an inline breaker or fuse in the (+) cable between the batteries and the main buss that might have tripped or blown (if a breaker it might have a reset button)

[July]

Hi!
It was stored for 1 year and a half.
It wasn't plugged during storage.
Batteries were on a charger in our garage, levels indicate they are full.
My husband will go tomorrow and try what you explained.
Thanks!
Julie

[July]

Yes, the switch is turned on.
Julie

[July]

Thanks Alan, we'll check that tomorrow!

[July]

So, there was voltage at the power center, but then after a while there was none. From what I understand, my husband thinks either all the fuses need to be changed, or the 50 amperes switch is faulty. He will go back later to check again.

One sure thing, batteries/cables are ok, and disconnect switch is definitely on.

He's thinking he will soon change the board for a brand new, modern one. The fuses we have are an old model, we don't even know where we could buy new ones. Any ideas?

We're definitely not going camping this week-end and I'll have to deal with 2 very disappointed daughters. :0(

[uncle_bob]

Hi

Ok, some basics:

The voltage you read at the panel comes from the charger / converter *and* from the batteries. If the batteries are charged, you should have 12V on the panel. If the converter is plugged into shore power, you should have 12V on the panel.

So, no voltage at all means that the batteries are dead and the converter is not running. Not an impossible situation, but unlikely. More likely is a loose cable running to the panel. Having all the fuses in the panel shut off then turn on ... nope ... they don't work that way. The panel could be damaged, or a connector on the panel could be loose.

How to proceed:

1) Monitor the batteries with a multimeter. See if they die after a bit. If they do, they either are dumping a lot of current or they are in need of replacement. Do this without being on shore power.

2) Plug into shore power while looking at the battery voltage with your meter. The voltage *should* rise when the converter is plugged in / turned on. If not, check at the terminals on the converter. If there is no rise there, check for 120V on the converter input. If that's ok, then the converter likely needs replacement.

3) If both converter and batteries are OK, then you do indeed have a bum cable or loose connection. These are always a pain to dig into. You very much need a wiring diagram to get the job done. You run along each cable until you find one with voltage on one end and a problem at the other. Not much fun ....

That's pretty much how it can be done. There are an almost infinite number of variations on what to do in which order. You still need to cover pretty much what is on that list.

Bob

[July]

P { margin-bottom: 0.08in; } So my husband changed the 50amp breaker, twice, and it still does the same thing: 12V works for 15 minutes or so, and then it goes off again. He tries the lights, fridge, etc., everything works but it goes out after a few minutes and doesn't come on again even though he unhooks the battery and hooks it back on. The new breaker is supposed to be a self reset breaker.


There is continuity in the 50amp breaker.
All cables are relatively new, and they must be working since there is continuity.
He redid the ground connection, sanded all contacts, and rescrewed to the frame.


Can the problem come from the disconnect switch??? It's just an on-off switch, it can't seem to be that.

[uncle_bob]

Hi

Ok, "the 50A breaker". In many trailers there are multiple 50A breakers There are often two type II SAE 50A thermal reset DC breakers. One is at the converter into the battery. The other is on the battery back out to the DC panel. If the trailer is a 50A system, it has two 50A AC breakers ...

So, if it's the 50A DC breaker *into* the battery (I'm guessing this is the one) then the battery is pulling > 50A for long enough to trip the breaker ( = your 15 minutes ). That suggests that the battery is pretty badly discharged or defective.

If it's the 50A type II out of the battery, you may be pulling more on the DC panel ( > 50A) that you think. Some work with a current meter would confirm or deny this. Most multimeters will not handle 50 amps. You will need something a bit more fancy to do this kind of measurement. This is a good one:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It's expensive and there are other outfits that make them.


Quick check - pull the battery(s) and see if you still have the problem. If so, find a clamp on current meter you can borrow. If that fixes it, get the battery(s) tested.

Bob

[July]

It's seems to be related to the jack! The problem happens whenever my husband activates the jack!

[GCinSC2]

Take batteries out of trailer, use a known charger charge batteries. After charger says charged have batteries tested. Most auto parts stores have tester.

Begin argument here About parts store tester equipment and employee training.

But it might show you something or charge and use old school battery hydrometer to check cells.

[CBWELL]

In your initial post you indicated that the batteries were new, fully charged and that your husband had tested them. When were they new, did you charge them, and was a load test done on them. Brand new batteries can fail, and if completely discharged, can be almost impossible to recharge properly. A load test is the only way to check for proper battery condition. Start with the easiest and most common electrical tests. Good luck!

[uncle_bob]

Originally Posted by July

It's seems to be related to the jack! The problem happens whenever my husband activates the jack!

Hi

On a normal trailer, there should be a fuse in series with the jack. Current practice is to wire them direct to the battery. Modern trailers run a jack through a 30 amp fuse. That's way below the 50A breaker. Since your trailer is 30+ years old, who knows how it is wired or if the "stock" wiring diagrams have any relevance at all.

So, If it's wired to the battery *and* the battery is charged, the fuse *might* blow if there is a problem with the jack. The breaker would never blow in this setup. If the battery negative is loose ( = battery is not fully connected) the fuse should still be what blows.

The converter likely only puts out about 30A or so. If the battery is MIA, then indeed, the converter will drop down to something pretty low with a 30A load on it. That would be a really good indication that the battery is not fully connected.

Simple answer is still to follow through a step by step process. See what is and what is not connected. That is the information that will let you fix the problem.

Bob

[RRwayne]

I thought I would add a comment I just had this problem. and I'm pretty savvy, all 120v was good, battery good all fuses tested and inverter checked out, yet when 120v was turned off the 12v went down, and in the older units not a lot of room to test it all, so I keep testing and found the ground fuse was testing but corroded enough not to allow full power pulled the fuse cleaned and it and contacts and it all worked.