Electric circuit testers troubleshooting

It's hard to follow what you were measuring. Were you measuring from the hot to ground or hot to neutral? Or were you measuring across the vacant fuse contacts?

If you are reading from hot to neutral, readings of 120 on one phase and 109 on the other would indicate a bad connection on the phase that's reading 109 volts. Please read my earlier post and make all the measurements I suggested. If you're not sure what's what, then you would be wise to leave it to a licensed electrician.

A reading of 1 volt rms on a digital multimeter is probably noise, indicating an open circuit. The input impedance of the meter is so high that it will measure voltage just from the noise picked up by the wiring. The receptacle tester has a lower input impedance and requires a certain amount of voltage to operate. Understand, however, that the purpose of the receptacle tester is NOT to determine if the circuit will provide adequate current. It is only meant to check that the receptacle has proper polarity and is grounded.

If you were reading across the two contacts for a single fuse, then you were not making a meaningful measurement. All voltage measurements must be made to a reference, usually neutral or ground (which should be the same).

In the case of reading across the fuse contacts, you can get readings anywhere from zero to 120 volts, but they are totally meaningless. For example, if all the loads on that phase are turned off, you would read zero volts, regardless of whether or not you have power. Turn on one load, though, and you'll read 120 volts even if there is a bad connection in the circuit.

I recommend you call an electrician on this. I'm afraid you're going to hurt yourself.

Charles

This is a great example of the amazingly good information you can get on this site---in case anyone didn't notice.

All the best, Stan

Do the following AC voltage checks:

Hot to Hot (should be ~240 Vrms)
Hot A to ground (should be ~120 Vrms)
Hot B to ground (should be ~120 Vrm)
Hot A to neutral (s/b ~120 Vrms)
Hot B to neutral (s/b ~120 Vrms)
neutral to ground (s/b 0 Vrms)

Check first with no load (breakers off), then with a load (breakers on). If at any time you get readings significantly different that what they should be, start looking for a bad connection.

Ive seen loose or unattached Neutrals happen so Id be checking the integrity (look for loose or arcing connectiions) at each n every Neutral connection in the panel and meter base etc.

Im unsure of the service entrance and panels n sub panels there, but you might wanna use a regular two wire tester or simple two wire voltage indicator lamp n check for voltage between the hot feeders n equipment grounds n neutrals at various locations to help track down the problem, but another problem is just cuz a low curent test lamp will glow dont mean the connections are good enough to work under normal higher amperage conditions.

John T