Your tester is meaningless. The amount of leakage to trip a GFCI is tiny. Does the thing trip when nothing is plugged into the receptacle? Are you using an "in use" cover? Are the cover and the box installed properly? Where is the charger sitting in all this?

If the breaker trips when you move the cord around (or plug or unplug), my guess is that you've got something touching inside the box (probably a neutral-to-ground fault). It's rare that a GFCI breaker goes bad. You can't replace it with a non-GFCI breaker unless you're assured tthat you have GFCI protection everywhere on the circuit that needs it. You have a very uncommon situation. At the time when the code permitted the bathroom and outside receptacles to be on the same circuit, GFCI breakers rarely were used. Someone has done some retro hacking on the stuff.

Thanks Ron. It's been working fine for a number of years. Just recently it started tripping the breaker. The charger for the cart is in a shelter logic shed with the cart. The extension cord is in some weeds/plants to that area. Haven't noticed that it trips if nothing is plugged into an outside GFCI outlet.

I'm assuming the box and cover are installed properly. My husband replaced the old one last week. That previous one was replaced by an electrician. Both of them are occasionally tripping the inside breaker. It only happens sometimes. If I didn't mention it, the bathroom also has a GFCI outlet. It's my understanding that the wiring to these places has been the same since the place was built in the 1970's. It's just strange that nothing has changed, except the GFCI breaker has started tripping.

Thanks for your help.

DH says copper.

As Ron said, GFI breakers seldom fail. GFI receptacles are another story, they are notorious for failures. So it could be the GFI, but more likely the GFI is telling you that something is really wrong.

Basic troubleshooting is in order. Ideally you'd measure the actual leakage current, but there's a simple if less accurate way.

If the GFI never trip when nothing is plugged in, disconnect the charger from the extension cord and plug the cord into the outdoor receptacle. If the GFI trips with the cord plugged in but the charger disconnected, most likely it's the cable; replace it.

A cable lying on the ground and/or in the sun for years will deteriorate and its insulation will fail. A much better and safer solution is to have a proper receptacle installed in the shed.

If the cord alone doesn't cause tripping, plug in the charger. If the GFI now trips, have the charger serviced or replace it.

A charger stored in a protected outdoor area can get all kinds of junk inside it -- cobwebs and mouse excreta and/or nests for example. These can get damp and cause leakage current.

If a mouse mama raised her babies in there, you'll probably decide to junk the charger. Cleaning up mouse urine and the resulting corrosion ain't no fun, and could be a health hazard.

Thanks David. You have some good suggestions. The shelterlogic shed doesn't leak, but there is a lot of dust and wasps, etc. I can see into the vents and it doesn't look too bad. I will try to plug the charger directly into the exterior GFCI, but that means I will have to leave it outside. We live in a very rural area, with a lot of wildlife, but they probably couldn't hurt the cart for a night or 2.

Like I said, my husband replaced the exterior GFCI last week and put a weatherproof cover over it, and we're using a new heavy duty extension cord, but it still intermittently trips the GFCI breaker. We aren't real mechanical people, so I wouldn't want to open the charger to clean it, but would it be okay to use an air compressor on it, or could that ruin it? Thanks for your help! We'll certainly call an electrician if we can't easily figure this out. I realize it's nothing to mess with for very long.