I don't know how the jack is wired, but I'd check the cables at the battery first.  Take them all off, clean them, put them back on and make sure they're tight.

TT

I'm not sure about the 171, but the power panel in the 179 has two 40A fuses in the middle. Check those. Then check to see if there are any lights beside any of the fuses on the right side (12V). Also, check all the wires for the 12V side to make sure they are in the right place and solidly attached. After making sure no live 110V power is connected, take the cover off the power panel to check this. I had one wire break off and although it looked attached, it wasn't.

Edit: Did you have power for the jack while the TV was attached or is power there when the TV is not attached also? Do you have a voltmeter? If so, please check your battery. If power was while the TV was connected, you could have a dead battery. If the battery/batteries check out, then wiring is likely an issue.

Have you checked your connections?  They can look good but not be.  At least try to wiggle each end of every cable.  (They shouldn't wiggle.)  The wiggle test isn't conclusive. 

TT

Originally posted by JoeSaint To eliminate the possibility of a bad disconnect switch, I took a car jumper cable and went across the two terminals and still nothing. The two fuses I checked were the 40 amp polarity fuse and the 30 amp main 12v fuse, both are good

Okay, how did you do that? Did you take one of the pair and connect one clamp to each terminal? Did you use one clamp to bridge both terminals?

My suggestion was to remove the switch from the circuit, not jumper it. Connect the RV's red positive cable to the battery's positive terminal and the white negative cable to the battery's negative terminal directly.

Do you have a multimeter? If not, head down to your local hardware place (Lowe's, Home Depot, Ace, Harbor Freight) and pick up an inexpensive multimeter. HF would probably be the least expensive place to get a cheap one that will be adequate for this purpose.

Take a DC voltage reading across the two battery terminals. If you have >12V, your battery is probably good. If <12V, it could be weak or dead. However, you say your jack works, so the battery is likely good.

While you are at it, check to see that you have the red wire from the R-Pod connected to the positive + terminal and the white wire to the negative - terminal. It is okay to take a jumper from the negative terminal to your cut-off switch and then connect the trailer's white wire to the other terminal. This is the safest way as the rule of thumb is connect negative last, disconnect negative first.

Set the meter for Ohms. Disconnect the switch. Take a reading across the terminals with the switch in the off position. The meter should give a reading of 1   . if there is no continuity (Cen-Tech Digital Multimeter used for reference set to 200K Ohms). Turn the switch to the On position. The reading should change to 00.0 Ohms. If it remains at 1, then the switch is bad. If the switch is good, then reconnect your jumper from the negative terminal and reconnect the trailer's white wire to the other terminal. Make sure no wires are shorting out against the frame. I don't know where your switch is mounted, but make sure nothing is shorting with it or its mounting either.

How did you check the 40A fuses (should be two)? Did you do a visual check or use a meter? If visual, use the meter to check each fuse. It can appear to be good but in reality be blown. I've had that happen. If, while you were putting in your battery cut-off switch, you managed to reverse the polarity, even for a second, one or both of those are blown to protect your converter.  The two are to the left of the larger stack of 12V fuses for the various appliances, lights, refrigerator, etc. If one is or both are bad, replace them with new 40A fuses.

For the regular stack of fuses, on mine, if a fuse is blown and there is still power available, an LED light will show next to the blown fuse. If you remove one of the fuses on the main stack, say the one for the Bathroom or Porch light for example, do you see an LED light next to the socket?

I just remembered that WFCO has a troubleshooting chart for their converters. You can find this http://wfcoelectronics.com/wp-content/uploads/2015/11/New-Flow-Chart-for-WF-8900-Series.pdf - flow chart for the WF-8900 here . The same chart is suitable for other WFCO models as well. That might be the better way to proceed with troubleshooting your power problem.