Sunday, September 2, 2012

No AC or DC Power

The situation: you are hooked to 110VAC but none of the 12DC appliances are working and the battery is down below 11 volts. Just as a check for the 110VAC power, make sure the display in the microwave oven is lit and that the air conditioner fan runs (i.e. at the start of a problem, look for the simple things and don't assume ANYTHING).

Both the refer and furnace always need 12volts to operate. Hooked to shore power or not.

If you do indeed have 110VAC power in the coach, it is apparent that the converter is not supplying power to the 12DC buss and the battery is now discharged. Check again to make sure all the circuit breakers in the power center are on. The handle of a tripped breaker can be wiggled up and down. A breaker is on when its handle is up. If a handle wiggles, push it down to the off position and then push it up.

Assuming that, that doesn't cause the voltage readout in the solar controller to read above 12 volts, it's time to check the fuses in the DC fuse panel. The two 30 amp fuses at the top of the panel are between the converter and the coach's 12VDC bus. Check to make sure BOTH of them are good. (They are in parallel so if one fails, the other will normally blow.)

If you 1) have 110VAC power, and 2) the 30 amp DC fuses are good, and 3) the DC voltage is still below 12 volts, there is a good chance the converter has packed up. Before we jump to that conclusion, there are some other things to look at before we are completely sure.First, do you have solar panels? If you do, and the sun is out, they should be providing some current and should keep the DC voltage higher than it might otherwise be. Does the solar panel controller show that there is current being sent into the system?

Second, if you start the coach's engine, does the voltage on the DC bus rise to something well over13 volts? IF the answer of either of these questions is no, then something else is either the problem or perhaps something else has failed at the same time (collateral damage?). For instance, there is a chance that the breaker between the battery and the DC distribution panel is open or that the solar panel fuse is blown. The breaker is typically in the back of the battery compartment or is accessed by removing the drawer below the refrigerator in a midbath and
perhaps other floor plans.

When you have 110VAC in the coach, if the converter is working, for coaches delivered after mid November of 2001, the voltage of the DC system should
be about 13.8 volts. That's the converter's nominal output voltage. (Earlier coaches have a different converter so the next two paragraphs do
not apply.)

But, even if it's working correctly the voltage may be something above or below 13.8 volts "for awhile". For instance, if you have been driving for
awhile and/or you have solar panels under a bright sun the battery's voltage may be higher than 13.8 V for "awhile" after you stop or until the
sun goes down. Then, the voltage should decrease to 13.8 volts.

On the other hand, if the battery is well down as you plug-in to 110VAC, even if the converter is working the voltage will not instantaneously jump up to 13.8 Volts. A working The converter, will put ~30+ amps into the battery which will cause the batteries voltage to jump up but it will not immediately reach 13.8 Volts. After "awhile", that is, as you watch, the voltage should rise bit by bit to 13.8 volts.

Note how useful a simple $10 multi-meter is for trouble shooting. First of all, if you don't have a built in solar panel controller voltmeter you can use a multi-meter to measure the DC bus voltage by measuring across those big square terminals at the lower right of the DC fuse panel. Knowing the DC bus voltage then you can then compare it with the voltage across the battery's terminals to see if the DC breaker is tripped. Or, one could measure to see if there was any appreciable voltage drop across the 30 amp fuses in the DC fuse panel to see if they are blown. Another use would be to pull the 30 amp DC fuses and measure from the top open terminal of one of them to the big square ground lug to see if the converter is making DC at all. Multi-meters are a really useful tool when trouble shooting.


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