They won't while still connected to gfci. To test them take wires out of gfci outlet. There's something in those that keeps them from a true read that why when you check the hot wire to ground you get a reading I had the exact same thing this summer with mine for our pool. Replaced outlet and all is well. If the gfci trips alot they go bad quick.
Thanks!! Will try that as soon as I get off work tonight, oh and do 3 transfers...
that GFCI kicks off if i miss emptying the skimmer... LOL