re:
Did you know all your GP's are wired in parallel?
(so, you'll have to totally remove the busbar or your (Ohmmeter) readings are essentially meaningless.)
Not 'meaningless'.
Say the GPs are 1.2 ohms each.
0 bad GP, 3 good will show 0.4 ohms
1 bad GP, 2 good will show 0.6 ohms
2 bad GP, 1 good will show 1.2 ohms
so you will know the condition of them, sort of. You won't KNOW which one is bad though
And of course there's the 'aging' effects,feed wiring condition, GP controller, as well as how accurate your DMM is. (You did short the leads to get the baseline resistance ,right ?? )
The better ( best ??) test is to split them apart, put an ammeter in series,one at a time, and see how much current the GP draws. I suspect about 10 amps is 'nominal'.