No solar input

 So far our trip has been uneventful due to having electric hook ups most nights.  But now we're past that part of the trip and need solar to charge batteries.  Last night the batteries got down to 77%.  We arrived just north of Tucson @ 92% after shutting off the  Ford motor the input light on our battery monitor shut off.  No solar in Tucson???  I don't think so!!  Am I missing something, a reset switch or fuse something else?

You do not describe what brand of charge controller or battery monitor system you are using nor the size of the solar panels.

There may be a fuse near where the wires from charge controller go to the battery.

Of course the other problems with solar panels is shading. Even if a small shadow is on the array you will not get any charging..

How far did you drive before shutting down the Ford?  77% to 92% seems odd to me unless it was a very short hop.  Normally if I drive a few hours batteries are back at 100%.  Just wondering if there is something else going on here.

Please let us know what monitor panel you have and what solar package.  There is a fuse in the solar feed line but unless something shorted out I don't see it blowing.  You can test by putting a meter on the feed lines.  Mine is under the kitchen sink but yours might be someplace else depending on what unit you have.

I have the two standard 150W panels PC installs with the Samlex solar charging kit and the Tri-metriC TM 2030-RV monitor.  We drove about 3 hours from point A to point B yesterday.  I've got a 2018 2552.  It just sat out in the Tucson sun for about 5 hours and lost 4%.  I don't have any of those electrical meters, it seems as if I need to purchase something and learn to use it.  What do you suggest?

I have the two standard 150W panels PC installs with the Samlex solar charging kit and the Tri-metriC TM 2030-RV monitor.  We drove about 3 hours from point A to point B yesterday.  I've got a 2018 2552.  It just sat out in the Tucson sun for about 5 hours and lost 4%.  I don't have any of those electrical meters, it seems as if I need to purchase something and learn to use it.  What do you suggest?

That tri-metric is really all you need to monitor the batteries.
Of course it must be set up properly, PLEASE read the manual for trimetric.
The push button switch in the middle allows you to switch the reading from your Ford battery voltage, if they wired that in, RV battery voltage, Current -Amps charging of - discharging and % charge.

So if you put in sun with set switch set to read amps you should see + flow of current, (with no shadows from anything, antenna, A/C or vents or trees) if battery is not fully charged you should get  +10 amps.
Look at RV battery voltage it should show 13.2v when fully charged or 14.7 v if batteries are charging.

A volt-ohm meter is (in my opinion) a required item for an RV tool kit.  You can easily pay $200 for a fancy one but you can get a functional one that does all you need for less than $20.  Harbor Freight has them as do most home centers / hardware stores.  I strongly suggest reading the manual completely if this is your first meter.

The three functions you will use are AC volts, DC volts and ohms.  Ohms is a measure of resistance and in this application is used mostly to determine if a wire is broken.  No resistance = good connection.  100% resistance = bad connection.  Middling resistance = something strange: call an electrician.

If I were diagnosing this I would set the meter to DC volts and start at the panels testing the plus side to ground at each point in the chain.  That should show you the voltage coming off the panels.  It should be in excess of 14 volts in full sun.  If you have voltage there then go to the next accessible point which is likely at the solar controller.  Again test.  If you have voltage then try resetting the controller.  If no voltage then you have a bad connection (or blown fuse) between the panel and the controller.  If there is voltage at the controller inputs then test the controller output.  If voltage there then test where the controller output connects to the battery, you will need to disconnect the controller from the battery in order to do this test.  Note that you can start this process in reverse as well start at the batteries then the controller.  All we are trying to do is isolate where the issue is.

*****  All this is meant as what I would do.  But I've been playing with electricity since I was 10 years old.  If you feel uncomfortable or not sure you can perform those tests SAFELY then get an electrician or RV mechanic to look at it.  It is 'only' 12 volts but that is more than enough to seriously harm if the amperage is high enough.  And you can also ruin gear if you stick the meter probes into the wrong place.

Well, we took the rig to an RV repair facility and found out that both panels are good but that there ls a short in the wire leading from the passenger side panel.  As soon as they disconected that panel we had input.  So we'll get by on one panel and have PC fix it right.  Thanks for all your input.  Jatrax, I'll look for the proper testing tools at a place that can show me how to use them safely.