Strange Electrical Issue

I am having a strange electrical issue with my 2003 Winnebago. Twice in recent months I have noticed the generator periodically surging and then it died while driving with the basement heat pump running. When hooked up to 50a shore power everything seemed to be working fine, then I noticed the panel says incoming power is 30a. Watching the monitor, when the heat pump kicks on it goes to the normal apx 17a draw. Then when the second compressor kicks in it fluctuates wildly, then settles on 2a rather than apx 23!  Again, the heat pump unit appears to be operating normally. So I unplugged and checked the outlet, power cord, etc with a multi-meter and  confirmed that normal 50a current is making it into the motorhome ...two lines of 120v 50a current. So I used an adapter to step the input down to 30a. Everything operated normally, including normal amps display on both one and two compressors. I removed the 30a adapter, went back to the normal 50a power cord, and again have apx 17a on first compressor and 2a with both running ...same is true whether running heat pump or ac.

What are the possibilities that are causing the monitor to read 30a when 50a is present? ...and why the very strange 2a reading with both compressors running??

2 Amps with 2 compressors running ???    Could be reading the neutral wire current.

If you are getting the amp reading off the Powerline (aka Intelletec) panel and connected to 50A service, it is indeed showing neutral wire amps. It is not supposed to display amps when handling 50A shore power, cause the neutral wire amp reading will always be incorrect in that case. On 30A shore power, and probably on generator (is it an Onan QD 7500?), the neutral wire reading will be accurate.

The neutral wire carries the net current between the two 50A hots. Since they are out-of-phase, the net will be near zero if both hot wires are powering something (one compressor each, for example). The genset power and 30A shore power are in-phase, so the neutral amps are correct.

After today's messing with it I believe the ATS is hanging on one leg.

When I went to check it again I found the display showing the normal 50a incoming power (rather than 30a as it said when I left it before). I ran ac/heat pump and all appeared normal, including the amps reading on one compressor and then on two compressors. I had NOT tried running on the generator, so I started the generator and shut off the breakers to the 50a outlet. When I got back in the coach I found the display telling me I was on BOTH 50a AND generator. I went out to the power bay and did several fist whacks on the ATS box. Back inside, and the display reads generator only. I ran both the ac and heat functions and all worked as normal. Then when I shut down the generator and turned the 50a breakers back on, the display is back to reading 30a incoming power rather than 50a.

I believe the ATS hanging with one leg on 50a and one leg on generator would explain the 2a reading when the 2nd compressor kicks in on 50a power ...as mentioned above, it is reading the neutral leg. AND it would explain the generator bogging down/being killed when the 2nd compressor tries to kick in on generator power ...one leg is hung up on the dead 50a connection. This Parallax ATS model 5070 was new in January 2007 after a lightning strike damaged the original.

Do you have a meter that reads frequency. Sound like it might be a little off on the generator also check the ground conections

In checking online I found that the Parallax 5070 I had was obsolete and the current replacement was the 503. I ordered it almost a month ago, but have not had time to get it installed until yesterday. We went to a rally a couple of weeks ago and since the display showed we had good 50a shore power before I unplugged at the house we did not run the generator driving to and from in hopes the ATS would maintain that position. All went well.

Replacing the 5070 with the 503 was definitely not a "direct bolt-in" replacement. After removing the 5070 I had to create a longer mounting board (3/4" plywood). Because all the connections were moved inside the 503 I stripped all incoming cables back several inches to get more wire length. I mounted the 503, and discovered I needed to get more wire length yet. That was a real challenge with the cable running into the coach ...the "load" cable ...but finally I managed to get enough wire to make the connections. The 5070 had all wires from each cable (line, load, gen) located together where that cable entered the box. The 503 groups the connections by L1, L2, and Neutral so when finished all red wires are together, all black wires are together, and all white wires are together. The ground connections are hidden behind all that by an insulating flap. That grouping made it harder physically to do the connections (had to have enough wire to reach the length of the box, leaving bunched wires in the middle), but easier to ensure I was not making a wrong connection.

When completed I exercised loads on both shore power and generator, watching the panel when switching from one to another. All operated normally.

I partially dis-assembled the old 5070 as you cannot see the points when the box is installed. I found no burned points, connections, etc. (also found no loose connections when taking it out). Everything looked good. Only thing I can figure is that one of the relays that do the switching was going bad.