Getting strange reading when I test a recepticle

[OutThere]

I have moved back to my house i was born in some 60+ years ago. Most of the original house's electrical receptacles are 2 prong with the center screw that holds the cover plate on as ground. They all test, OK. My parents had an addition installed on the second floor sometime around the mid to late 60's. Then we also had a second addition for a TV room and storage area 1st floor and 2nd floor. so this second addition was done by a neighbor up the street in the early 70s, that did this type of work for a living. So all the outlets the receptacles they installed (3prong) and lighting seems to be 120vac from neutral to hot, around 90vac from hot to ground. approx. 30vac neutral to ground. I plugged in a receptacle tester and both yellow lamps came on indicating correct wiring. So what do you think?

 

[davesparks]

I would suspect an earthing/grounding issue, either with the earth rods themselves or with the neutral/earth link.

 

[OutThere]

I would suspect an earthing/grounding issue, either with the earth rods themselves or with the neutral/earth link.

could it be at the fuse box? i know if i short one of the receptacles that the circuit breaker will trip.

 

[Megawatt]

I have moved back to my house i was born in some 60+ years ago. Most of the original house's electrical receptacles are 2 prong with the center screw that holds the cover plate on as ground. They all test, OK. My parents had an addition installed on the second floor sometime around the mid to late 60's. Then we also had a second addition for a TV room and storage area 1st floor and 2nd floor. so this second addition was done by a neighbor up the street in the early 70s, that did this type of work for a living. So all the outlets the receptacles they installed (3prong) and lighting seems to be 120vac from neutral to hot, around 90vac from hot to ground. approx. 30vac neutral to ground. I plugged in a receptacle tester and both yellow lamps came on indicating correct wiring. So what do you think?

To start with if you change your receptacles to 3 prong without a grounding conductor then by code you have to install GFCI receptacles with a sticker indicating no equipment ground. If the receptacle is reading correct with your test instrument then someone has installed a jumper to the ground screw from the neutral which would fool your tester to indicate that that they are wired correctly and has an equipment ground.