[dobiefloyd]

I have 4 year old husky air compressor that quit working. I thought the motor burned up so took it in to have fixed, hooked up power and worked fine. The guy says it's my power source. It's a 240v motor 15 amp wired directly to my panel with separate breakers. I have 119 volts at each wire through the pressure switch and to the motor. Plenty of power so I take it back. He puts power to it and no problem. Anyone??

[crigby]

Hi,
Might seem like a stupid question butyou say you have 119 V to each wire. I assume that is to neutral; how about to each other? Is it 238 V, the sum of the voltages as it should be?
Peace,
Clarke

[dobiefloyd]

That is was the guy at the shop asked. I don't get anything between them. I'm not sure if my meter is in the wrong setting or?? But if I had power from both wires from two separate breakers I would have to have the 240? It was fine and then quit.

[crigby]

Hi,
Well, a bit mysterrious here. Yes, you should get a reading that is the sum of the voltages, a out of limits, or a no connection reading. If you get no reading, it would indicate the last one.
One must look at the facts! It does not work for you on your site. It does work at the shop. This would lead one to believe that it is a problem a local problem, not an equipment failure.
Now the electrical side, the wires(sight unseen) should probably be black, red, white and green, or some semblance. The black and the red wires should have the voltage potential on them(the 120V) when each is measured to the white(or green) wire(s.) The white wire is termed the neutral wire(meaning the voltage flows back through it, and it is virtually at ground - the green wire.) This said; measurements black to white and red to white should be 120V, and measurement black to red should be 240V. Remember this is a measure of potential(the voltage available) and not actual flow.
Now you say it did work; has anything changed(other than not working?) The way that breaker boxes are made, the breakers must be side-by-side, or have two spaces between them. The spaces alternate in the breaker box. 240V comes in and is split for normal household current. Ranges, dryers, water heaters, etc. require two breakers or a double to get their 240V.
You can measure the voltage at the breakers by removing the cover(care MUST be exercised as there are "live" circuits there. With the cove removed, you will see many wires. Black ones(and maybe red) will fasten to a screw at one end of the breaker. These are termed the "Hot" wires. The white wires will fasten to a neutral buss bar at the top or bottom of the box usually. Measurement from the breaker(s) in question to the buss bar should be 120V. Measurement to the "Hot" screws of the two breakers should be 240V.
Breakers do go bad. They can break good contact where they plug into the "Hot" buss bars, yes there are two of them also that are generally concealed by the breakers themselves.
Power should be OFF before proceeding with an examination of the breakers. Generally they anchor and pivot at the centermost end and are pivoted horizontally at the outermost(left or right) edges. Main breaker should be turned Off, and verified with meter that voltage is not present. Only then can you unfasten the "Hot" wire to the breaker and pry it out. Look for burned or discolored contacts at the end where the wire fastened. One will probably have this if the problem lies there. Breaker boxes and breakers are brand specific; there are more than one design, and must be replaced with like breakers. Always take the old one with you for comparison, assistance.
Now, if any of this sounds like something you do not personally want tackle; then by all means do not.
The evidence that you have given me tell me that the problem is local and not with the equipment. If something works one time and then does not; the appropriate question, in this case, is: "What has changed?"
Hope that helps!
Peace,
Clarke

[dobiefloyd]

Clarke,
Been through all that. I have tested the voltage at the breakers, both good. When I test both my meter in the same setting reads 0 just like it wasn't hooked up. I know it a good connection because it works for wire to ground. My meter isn't the best but regardless I know I have power in the wires, Right? I have a black, red, and green wires, only 3. There is one space between them when I installed them in the box but what would that matter? This doesn't make any sense to me, Thanks for the help.

[crigby]

Hi.
If you put a space between the breakers it puts them on the same 120V circuit, they alternate. That would give you a 0V reading since that is what you have. Green is also functioning as neutral in your case.
Peace,
Clarke

[dobiefloyd]

Okay, I will buy that but it did run fine like that for 6 months?

[dobiefloyd]

Clarke,
Just went out to the garage and put the breakers side by side, works fine. Thank you! I have wired a lot of a/c units and sub panels but have never spilt the breakers before (usally use a double pull) causing this problem. I was sure that was how it was hooked up but I may have changed it because /i am short breakers so I have to borrow a couple when I need the compressor. I guess it would be imposible to run like I had them with the split? Again Thank You very much... I learned something new today, and very important when messing with wires!
Al

[davewee]

This condition can also be indicative of having one 120V line down. Measuring my failed AC outside unit showed me exactly this condition. 120V on each line to ground, but 0V between them. As it had worked for a few years and I'd made no electrical changes I knew it couldn't possibly be that the two hot lines were on the same phase. It was only when I pulled the fuses and checked each that I found one was blown. The 120V appearing on the 'dead' line was voltage fed back to the line through the capacitor/start/motor circuit.

[hkstroud]

Welcome Dave.
You have to look at the date of postings. This one is 1 1/2 years old.

[davewee]

Fair point, Harold, but when you search the net it doesn't generally give results by date, but by relevance. So anyone searching for answers to a similar problem on Google is actually more likely to come across an old thread than a new one. That's how I found this thread originally, in fact, before I figured out what was happening myself... I only signed up to possibly help out the next person to search for that particular situation, not just the original poster. I came across a similar problem on another forum that was from 2001! The answer was still relevant, though.

It's been a long time since I worked on mains voltage equipment with AC motors and relays and stuff, rather than solely on low voltage electronics as I do now, but it came back to me why I used to carry two meters, a dvm and an old analog meter. The lower input impedance of analog meters often drops stray and inducted voltages enough that that they disappear, but that digital meters display. In my case, I bet an analog meter would have shown instantly that one of the legs was down, whereas the dvm puts almost zero load on the circuit and therefore sometimes displays a 'phantom' potential.