Outlet tester shows faulty ground but only when associated circuit has a load on it..

[roy25101]

During a residential inspection of an out building, every outlet tested shows a faulty ground but only when there is a load on the circuit. If all loads are removed the ground shows to be fine. Any input on this one would be greatly appreciated. An interesting note, when a load is placed on the circuit, the tested resistance between the neutral and ground increases.....
Thank you..

 

[Little Bill]

Since there is no "how to" question, I'll allow this.

 

[kwired]

Low enough impedance in the EGC to test good, but high enough that voltage difference between neutral and EGC changes too much with a load on the neutral and it gives a fail on your tester.

One possiblilty I see is that you don't have a low resistance EGC all the way back to the system/main bonding jumper. This could very well be the case if you have the EGC tied to a ground rod and nothing else going back to the source - or something similar.