HELP, no DC power

[jdanielii]

Had my 25' Safari stored for a couple of weeks, when I brought it back up DC cycled off a couple of times but AC was fine. Now I am in it and DC has been lost a couple more times. All breakers and fuses OK. Battery has full charge and tests good. Need help!!!!

[Phoenix]

If your Airstream was in storage for a couple of weeks, you did NOT disconnect the batteries (physically, or via some type of switch; e.g., marine battery isolator switch), and your Airstream was not connected to shore power (or your batteries connected to a battery charger), I suspect that one or both of your batteries are dead.

How did you determine that the batteries have a full charge?

For a day or two, I'd let the batteries charge via the converter (with shore power connected), or disconnect and charge them with an automotive battery charger, before doing anything else. They may just charge up and be fine.

Just curious; how old are your batteries?

[jdanielii]

The battery is one year old.
If I am connected to shore power shouldn't the converter run the DC and charge the battery. The DC goes off and stays off for long periods then for no apparent reason comes back on.

[Melody Ranch]

Sounds like a Converter problem....tied in with a possible battery problem. Disconnect the AC and see if the battery will support the DC system....and for how long. What converter do you use? It may not be charging the battery either.

[Aage]

jdanielii,

What year is your trailer?

By the way, since you appear to have bought a trailer, you can now update your profile to show what trailer you have.

[Protagonist]

Originally Posted by Melody Ranch

Sounds like a Converter problem....tied in with a possible battery problem. Disconnect the AC and see if the battery will support the DC system....and for how long. What converter do you use? It may not be charging the battery either.

The converter may have a temperature-sensitive relay, that shuts it off if the converter overheats, then resets after it cools down. That would certainly explain the on-again/off-again symptoms.

[garry]

If you have a later model converter it probably has a temperature controlled fan if it does not come on when the converter gets hot or overheats the converter will shut down until a lower temperature is reached.

You can Google the converter and probably get the manual to check it out.

[Steve Bryant]

Here's the approach that I would take in troubleshooting this problem:

1. Disconnect the trailer from shore power.
2. Make a voltmeter adapter for a DC power outlet from a plug designed for a cigarette lighter (use something like this unit from Radio Shack along with a couple of wires to attach to your voltmeter leads http://www.radioshack.com/product/index.jsp?productId=3806057&znt_campaign=Category_ CMS&znt_source=CAT&znt_medium=RSCOM&znt_content=CT 2818117). This adapter isn't absolutely if you're used to taking a voltage reading from the battery cables themselves or from a power outlet.
3. Make a chart to record the following:
   1. shore power disconnected and no load on batteries
   2. shore power disconnected with furnace blower running
   3. shore power connected with furnace running
   4. shore power connected with no load on batteries
4. Plug the voltmeter into a DC outlet and record the DC voltages on the chart.
5. The results should be approximately as follows:

a) shore power disconnected and no load on batteries, 11.5 to 12.5 Volts
b) shore power disconnected with furnace blower running, 10.5 to 11.5 Volts
c) shore power connected with furnace running, 13.5 to 14.5 Volts
d) shore power connected with no load on batteries, 13.5 to 14.5 Volts.

6. Here are the primary issues to further investigate in each step if the voltage is not in the range listed in 5 above:

a) If voltage is below the listed range, pull the battery/batteries and have the specific gravity checked.

b) If the voltage is below the listed range after approximately 30 seconds of furnace operation, pull the battery/batteries and have the specific gravity checked. If the specific gravity of the batteries is good, I’d start to suspect wiring problems.
c) With shore power connected, the voltage should jump up to the indicated range. If not, the DC converter/charger should be checked for proper operation.
d) With shore power connected, the voltage should jump up to the indicated range. If not, the DC converter/charger should be checked for proper operation.

This is not an exhaustive troubleshooting approach, but it at least covers the basics and I hope that it is helpful.

Steve

[bwoodtx]

In an electrical problem it is possible to have voltage but no/minimal amperage. If the battery has a bad cell and is hooked up to the univolt it will show voltage, but may not have enough amperage for the load. Just ran into this with an Argosy I am rebuilding. Had voltage at the battery, the fuse board, but the lights were dim. Load tested battery-had a bad cell, replaced and changed out the wires from the battery to the fuse board-now I had amperage(current)-everything worked! If checking things with a volt meter, switch it to Amps and check.

[Steve Bryant]

jdanielii,
I've re-read your post and I've decided that you don't need to do everything that I said in post 8 above. I'm leaving the post up as I still believe that it contains some good basic troubleshooting information for problems of this sort.

You stated that the battery tests good, so I'm assuming that someone has tested both the voltage and specific gravity to verify each cell and the true state of charge of the battery. Assuming a good battery and the intermittent nature of the problem and that when the battery voltage comes on that it is sufficient, I think that you have a wiring problem (it could be a switch or connector). The converter output is only connected in parallel to the battery like a generator or alternator on a car. When the trailer is plugged into shore power, the battery is still in the circuit and is not disconnected during recharge. I suspect that if you are on shore power and the 12 volt circuits go dead you would not be able to restore DC operation by simply unplugging shore power.

[Phoenix]

A battery can also show a full charge, but be unable to deliver full current (amperage) because of dirty and/or loose battery terminals. You might want to try cleaning the battery cable connectors and making sure that they are tight.

[jdanielii]

Thanks for all of your responses. I have a battery tester/charger which I used to test the battery in the circuit and isolated. The battery was fully charged and tested good, it is a deep cycle marine battery and is only one year old. Whenever the DC would cycle back on it appeared to be at full power, ie all dc devices worked. The converter is under the goucho, so I got under there and tightened all of the connections that I could. One thing that I have noticed is that I haven't heard the fan on the converter for a while. I am going to test it to make sure that it works. When I got done tightening everything and brought it back up the DC worked fine, it has been on for nearly 24 hrs now. I hope it stays on. Will let you know about the fan shortly.

[TG Twinkie]

The fan in the converter does not run continuously under normal conditions. The fan will run to cool the heat sinks (like radiator) when the load on the converter is high enough to cause heat to be generated.
The converter will put out between 13 .5 and 14.5 volts when in operation. You can test the voltage at the fuse panel. Of course you must be connected to shore power for the converter to work.

[Silver Hawk]

Also could be a poor ground -

[jdanielii]

DC has continued to work after I tightened all the connections under the goucho. The fan is cycling when it gets hot. Thanks for all the input.

[Steve Bryant]

This is great news!

Steve