Hi last time away in my motorhome the pleasure battery was not charging from the solar panel and the voltage showing on the controller was jumping all over between 11 and 17 volts. When home I cleaned the panel which did increase the voltage. But the controller is only showing 12.7 volts at the terminals for the solar panel input on the controller but if I remove the wires I am getting 20volt when putting the voltmeter directly to the wire ends. Note it was very overcast when checking. Is this a fault on my controller,
No, it is more likely a fault in your panels or panel wiring. If you have a poor connection with a high resistance it can let enough power through for a voltmeter reading (this needs a very tiny current) but as soon as you try to charge the batteries not enough power ets through so the voltage drops to 12.7V, the battery voltage.
I disconnected the solar positive wire from the controller and had 20 volts at the end of the wire but as soon as I put it back in the controller and put volt meter to the screw in the contrit dropped to 12.7 volts as I said it was a very overcast day. I will check again on a brighter day and check the voltage again.
It sounds like a fault in your solar panel.
If you were to connect a power supply with approximately the same volts/amps that are expected out of the solar panel, this would be one way to test to see if the problem is with the solar charge controller. If the solar charge controller perks up and starts sending current to the battery, then it’s your panel.