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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7649
Experience:  Proven Professional 48 years Experience
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Blue wire when changing from magnetic to electronic ballast

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Why do I have one extra blue wire when changing from magnetic ballast to an electronic ballast single lamp?
Hi, I'm Mike and I'll be glad to assist you. The 2 ballasts wire differently. The new ballast is a T8, I would assume and the old one was a T12 - correct?
Customer: replied 5 years ago.
No, I positively have a proline called GE 140RS120-diy and it says T12 at the end.
two red to the lamp, two blue to the lamp and then it has one white wire and one black wire. On the old ballast there is one less blue wire.
There should be a diagram on the ballast. It is wired withe reds to one socket and the blues to the other socket. The black and white are the 120V Line.
Customer: replied 5 years ago.
This is exactly how it's been done. This is no help so far. By the way I have changed out the light sockets but the light still doesn't come on.
Customer: replied 5 years ago.
schematic is too small to read and the "view full image" only brought back "Bad Request"

Our schematic does not match what you have sent.
You must have a bad connection. The ballast wires exactly as instructed. See the link below and enlarge the picture to see the diagram.

GE 72110 GE140RS120-DIY LFL ProLine Electron - -
Customer: replied 5 years ago.
The diagram is the same as the old ballast. I still do not know why I have one extra blue wire on the new T12 ballast.
Customer: replied 5 years ago.
I have it hooked up exactly as the diagram. I have a wire tester and I am not receiving a hot feed.
Do you have a 2 wire voltage tester? If so check to see if you have 120V on the feed. Then check the lamp for continuity between the pins on each end. The last thing to check is that the wires are connected properly in the wire nuts.
Customer: replied 5 years ago.
I have 120V on the feed. We put new lamp holders and we've tried new and checked lamps. All of the wire nut connections aregood. I only have power in the black wire.
The socket you installed are they shunted or not? T8 need shunted sockets and T12 don't. They look the same. The differenceis that the 2 wires on a socket either are idependant of each other or are shunted together. You'll need to check the wires on each socket for continuity - let me know.
One more thing - The color of the label indicates the voltage of the ballast. 120V need to be Yellow.

72110 - Specifications - GE Commercial Lighting Products
Customer: replied 5 years ago.
We have already installed two others in two other fixtures that work, same model same everything. I checked the continuity of the sockets in question and not getting any reading.
There are only a few possibilities left.
  1. bad connection on the wires
  2. No ground to the fixture
  3. Bad Ballast.

If you wired the others with the same ballast, did they have an extra blue wire?

Customer: replied 5 years ago.
When we switched the other two sets of lamp holders we used the original ballast, not one of the new ones. Have double checked my ground it seems to be good but at this point there is no doubt that I have a bad connection some where....What are the possibilities of this brand new ballast being bad from the factory?
With all the junk we get from China, very good possibility.
Customer: replied 5 years ago.
If I'm not receiving a volt reading in the red wires does that mean that the ballast is bad or is there some other way you can tell me how to check the ballast?
That would indicate it failed.
Mike G. and other Electrical Specialists are ready to help you
Customer: replied 5 years ago.
Are you willing to wait until we replace this ballast with a new ballast that we have on hand to make sure that the problem is the ballast?
What ever you feel comfortable in doing.
Customer: replied 5 years ago.
Thank you for your help. The new ballast produced light. That was definitely my last resort but it was hard for me to belive that a brand new ballast would result in this much trouble. We also found that three of the lamps in a ten pack were also bad. Again thank you for your time and patience.
You're welcome. I can't count the number of times I've had bad parts.