Electrical problem

[dlmead@earthlink.net]

I have an electrical problem in that when I plug into shore power or run the generator, I loose one of the circuits in the coach - the circuit that operates the refrig. All other circuits seem ok. When I am on the inverter only everything works fine. Also it seems now that the shore power is not charging the batteries. This problem developed at the last day of a week-long trip. Any ideas as to where I should look before I haul it to the shop?

Don

[wolfe10]

Don,

There are many ways your 120 VAC could be wired to the inverter and refrigerator. I am assuming that when you say you loose the circuit that operates the refrigerator you ARE talking about the 120 VAC circuit.

Is your inverter output wired through a sub-panel? If so, are you sure that no other circuits powered from the sub-panel are dead?

When you say you "loose one of the circuits" does it trip a breaker or GFI-- if not, what does it trip?

If it trips a GFI, turn off 120 VAC including the inverter. Use an ohm meter to check the refrigerator 120 VAC heating element. Disconnect the two leads to the 120 VAC heating element. Check between them-- either 0 or infinity ohms indicates a bad element. Now check between each lead and ground (metal surrounding refrigerator flue). If any reading other than 0, the heating element is shorted to ground. And if the path to ground is slight (a mud dubber nest for example), it may be enough to trip a GFI but not enough to cause a problem on the inverter. This is just one of the many potential causes of your problem.

The more facts you give us, the better we can help you.

Brett Wolfe

[dlmead@earthlink.net]

Brett,

Thanks for the reply.

I checked the refrig as you suggested, it does appear that this is a problem as I get no ohm readings. This element should be relatively easy to replace.

However, regarding your question as to tripped breakers - I cant really find any "tripped " breakers or gfi. The only thing i can find is that one of the two 40 amp "breakers / switches " in the box where the shorepower comes into the coach does not seem to engage or trips out when shorepower is applied.

I have unplugged and disconnected the 120v leads in the refrig, however, the problem with this circuit and switch continue. I would have thought disconnecting the 120 to refrig would alleviate the problem - no ??????

Thanks, Don

[wolfe10]

Sounds like the breaker that partially trips may be bad. I would replace it. Breakers DO occasionally fail. Any electrical parts house should have those breakers.

And while you are there, tighten all connections in the 120 VAC breaker box-- I do this annually. Obviously, do this with the shore power cord and generator off/disconnected.

Brett Wolfe

[seajaycecil@yahoo.com]

One more tiny bit of advise concerning the ''breakers''....

Unplug from shore power and take the front off your electrical panel

DID YOU UNPLUG FROM SHORE POWER???????

ok you are unplugged I hope. If not, its been nice knowing you.....

Anyhow, Usually these breakers are installed on ''blades'' and hooks

The ''blade'' is the HOT SIDE where the electricity comes in.

The ''hook'' is the thingie on the end of the breaker that you hook the

back end of the breaker on the panel. No power there.

Look at that ''blade'' in the panel with a flash light. Be sure it is not burned or blackened

in any way. This can be a source for low power or failed breakers.

go to napa and get some ''electrolytic grease'' It comes in a tube like toothpaste

Put a dab on the slot in the breaker body and a dab on the blade and

re-install the breaker and check to see that the screw in the end is tight

against the wire.

Check this about once a year WITH THE SHORE POWER UNPLUGGED. and tighten

all the screws with wires under them.

There will be a ten cent charge for this advise. You can pay me later ...

Seajay the sailor man

[tbutler]

While you are unplugging the shore power, you did unplug the shore power didn't you?? Be sure that the generator isn't running and won't run if you have an automatic start on your generator. Also, be sure your inverter is turned off before starting any electrical repair on the 120V AC current in your motor home. Any one of the three sources mentioned here could make for a very unhappy ending. After making sure you have no current coming from any of the three sources, use a test meter to determine that you absolutely have no AC current before touching any electrical component. Better safe than sorry!

[seajaycecil@yahoo.com]

Gooooooooooooood advice Tom. I dont have an ''auto start'' on my generator or a ac inverter so I failed to mention them. Thanks for the input on this and I reduce my ''advice price'' to five cents and I can be paid later ...

Seajay the sailor man

[dlmead@earthlink.net]

Here is update.... I finally had to engage the services of a competent RV tech - after considerable trouble shooting, we concluded the transfer switch box had some "phantom" problem , could not determine what it was but replaced the whole transfer switch box and that solved the original problem with the 120 circuit.

As luck would have it , now I may have a problem with the inverter ! With shorepower and generator off and the inverter on , the circuit voltage goes crazy - up to 140 volts and then back down to 125 over a period of time.

Is this a sign of failing inverter ????

don

[tbutler]

Don, thanks for the update. It helps us all to find out what the solution to your problem was. Now we have another suspect to put on our list of possible faulty electrical components. Unfortunately, it sounds like a trip back to a competent RV technician is in order. If the inverter isn't failing, it is surely malfunctioning.

[ClayL]

Here is update.... I finally had to engage the services of a competent RV tech - after considerable trouble shooting, we concluded the transfer switch box had some "phantom" problem , could not determine what it was but replaced the whole transfer switch box and that solved the original problem with the 120 circuit.

As luck would have it , now I may have a problem with the inverter ! With shorepower and generator off and the inverter on , the circuit voltage goes crazy - up to 140 volts and then back down to 125 over a period of time.

Is this a sign of failing inverter ????

don

If you have a MSW inverter and you are trying to read the inverter voltage with a digital voltmeter some inverters can cause some strange readings. The waveform will change with changes in load and the reading can vary quite a bit.

You really need to use a true RMS meter to get an accurate reading because of the distorted waveform.