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Topic: Diode in bathroom fluorescent wiring? (Read 639 times) previous topic - next topic

Diode in bathroom fluorescent wiring?

1998 U-320 36'

Today I was looking over the fluorescent ceiling fixtures in preparation for adding LED light strips and I came across some wiring I don't understand.

Our bathroom ceiling light (the one between the shower and closet) has a diode connected between the positive and negative wires at the butt crimps where the coach's 12 volt feed wires connect to the ballast wires.  This is the light that is activated from a switch in the bedroom, and also by a switch in the bathroom.

Does anybody know why a diode would be placed here?  Is this standard on all coaches?

Thanks,
Chris

Re: Diode in bathroom fluorescent wiring?

Reply #1 –
On Fri, Apr 14, 2017 at 8:56 PM Numbers via ForeForums  wrote:

Quote

1998 U-320 36'

Today I was looking over the fluorescent ceiling fixtures in preparation for adding LED light strips and I came across some wiring I don't understand.

Our bathroom ceiling light (the one between the shower and closet) has a diode connected between the positive and negative wires at the butt crimps where the coach's 12 volt feed wires connect to the ballast wires. This is the light that is activated from a switch in the bedroom, and also by a switch in the bathroom.

Does anybody know why a diode would be placed here? Is this standard on all coaches?

Thanks,
Chris

1998 U-320 36'

Hi,

Possibly to prevent "back EMF" (electromotive force) from spiking other lights (such as the floor illumination). The water pump does this on my coach. We are also used to separate multiple switching choices.
Jim

2002 U320 42'
Jim Frerichs
2002 U320 42'

Re: Diode in bathroom fluorescent wiring?

Reply #2 –
Chris,

That would be a Zener diode.  This is old school for voltage control.  The ballast in the fluorescent light can't stand the voltage swings in the 12VDC system so this is there to keep the magic smoke in the ballast.

And yes they are hid all over your coach, ours too, along with others. 

Pamela & Mike

Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Diode in bathroom fluorescent wiring?

Reply #3 –
Thank you both for the replies!

Would you recommend keeping these diodes in place if the ballasts are being removed, and the light changed over to 12 volt LED strip lights?  Seems to me that it wouldn't hurt to keep it in the loop.

It's been a long time since I released smoke from a circuit.

Chris

Re: Diode in bathroom fluorescent wiring?

Reply #4 –
When we went to LEDs we left ours.

 By the way I checked the breaking point and they should break around 12.6 - 12.8 volts. This will help the driver on your LED to not have to work as hard.

Seems like I posted a link some time back that had a simple explanation of the Zener diode but I don't seem to be able to find it tonight. Could have been on another forum though.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Diode in bathroom fluorescent wiring?

Reply #5 –
On Fri, Apr 14, 2017 at 9:19 PM Numbers via ForeForums  wrote:

Quote

Thank you both for the replies!

Would you recommend keeping these diodes in place if the ballasts are being removed, and the light changed over to 12 volt LED strip lights? Seems to me that it wouldn't hurt to keep it in the loop.

It's been a long time since I release smoke from a circuit.

Chris

1998 U-320 36'

I agree with the zener diode use. Sorry I misunderstood.
Jim
Jim Frerichs
2002 U320 42'

Re: Diode in bathroom fluorescent wiring?

Reply #6 –
Thanks Mike and Jim.

Below is a photo.

This is the only fixture where a diode is visible.  At first I thought it was because this light was setup with 2-way switches, but the light in kitchen area is also setup with 2-way switches and does not have a diode wired in like this.

For those not familiar, the diode is the black barrel looking thing connected between the white and black wires.

Chris

Re: Diode in bathroom fluorescent wiring?

Reply #7 –
Quote from: Numbers –
At first I thought it was because this light was setup with 2-way switches, but the light in kitchen area is also setup with 2-way switches and does not have a diode wired in like this.

Chris,

The one in the kitchen light is in the wiring conduit. (unless they hid it somewhere else in your '98) If you have enough slack you can pull the wire and the diode is hid about 3" back. I have seen several coaches that you don't have enough wire to be able to pull the diode clear of the end of the conduit which makes it a pain to deal with.

Man it was a long day yesterday, no wonder I couldn't find the post as my spelling had went to bed last night early. Here is a link to the post I had mentioned.  Diode  for you to look over in your spare time.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."