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Author Topic: Location of ground wire for galley/dinette ceiling lights?  (Read 3649 times)

Dougie Brown

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Location of ground wire for galley/dinette ceiling lights?
« on: February 12, 2017, 01:34:23 AM »
Anyone know if the ground wire for the two tube ceiling lights for the dinette & galley areas in a 37G are next to the hot wire (i.e. behind the central panel) which is switched next to the sliding door into the bath hallway?

Dougie.

edit by staff - changed message icon to topic solved
« Last Edit: February 16, 2017, 06:29:31 AM by John Canfield »
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #1 on: February 12, 2017, 06:43:51 AM »
Generally speaking Winnebago usually runs positive and negative wires together. You can probably find the actual wire location on your 12V house wiring installation diagram.
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Great Horned Owl

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #2 on: February 12, 2017, 07:43:08 AM »
It is possible that the frame is used sor some of the negative runs.

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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #3 on: February 12, 2017, 07:55:08 AM »
The frame/chassis is the same electrical potential as -12V but I can't recall Winnie ever using frame/chassis for the negative side. I think that could cause problems with ground loops if some bonding failed at certain points. As an EE, I'm sure you can imagine a few more potential issues with that.



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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #4 on: February 12, 2017, 10:52:32 AM »
I checked the wiring installation drawings before posting, and they don't help. Reason for asking is I've fitted LED substitutes in the light fittings after removing the tube assemblies, and whilst they're awesome, they get very hot indeed due to the 13+V supply whilst on hook-up (max is 12). They pull 4A as I've fitted nine of them in parallel. After looking at (& playing with) various solutions e.g. zener diode, voltage regulator, resistors etc., I succumbed to ordering a cheap-n-cheerful (and clunky-n-ugly) 12V/8A dimmer which requires both pos and neg; it switches the pos and dims the neg.  I thought I'd ask before pulling the panels apart. Thanks.
« Last Edit: February 12, 2017, 10:54:55 AM by Dougie Brown »
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cbeierl

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #5 on: February 12, 2017, 11:30:13 AM »
Winnebago does label every 12V wire every few inches, so that is very helpful in figuring out which wire does what.

Looking at the Body, 12 Volt Wiring Diagram for your coach it looks like the hot wires are PURple and the ground ones are GReeN.  This diagram also identifies the physical location of each wire junction/plug, etc.   The Body, 12 Volt Wiring Installation for your coach will give you some idea of where the wires are run.

It's also helpful to refer to the Wiring Identification Guide to see what each wire does.
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JohnDale

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #6 on: February 12, 2017, 11:55:21 AM »
I checked the wiring installation drawings before posting, and they don't help. Reason for asking is I've fitted LED substitutes in the light fittings after removing the tube assemblies, and whilst they're awesome, they get very hot indeed due to the 13+V supply whilst on hook-up (max is 12). They pull 4A as I've fitted nine of them in parallel. After looking at (& playing with) various solutions e.g. zener diode, voltage regulator, resistors etc., I succumbed to ordering a cheap-n-cheerful (and clunky-n-ugly) 12V/8A dimmer which requires both pos and neg; it switches the pos and dims the neg.  I thought I'd ask before pulling the panels apart. Thanks.

I installed LEDs and may be the same dimmer.I had to remove the ground wire off the very front light that the switch by the door. Then ran that ground to the frame on the front AC and everything works great. If you need pics let me know.
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #7 on: February 12, 2017, 12:03:44 PM »
Here's a 5 amp buck-boost DC converter 6-35V. A whopping $8.66 (eBay) with free shipping.  :D
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #8 on: February 12, 2017, 01:48:37 PM »
Chris, your links are exactly the ones I've been using. Despite showing as purple, they are in fact yellow but that's ok. 🙄

John D, I've no plans to dim the front-end light on that door switch as it's never on long enough to get intolerably hot.

John C, thanks for the link! Hadn't seen that piece of advanced technology so I'll have a look at one.  Here's what I bought from Amazon although they're on eBay too (I can't afford the kind of money you spend :D). I'll be hiding it behind the panel and showing only the spindle & knob.
« Last Edit: February 12, 2017, 01:51:44 PM by Dougie Brown »
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #9 on: February 12, 2017, 04:26:49 PM »
John C, thanks for the link! Hadn't seen that piece of advanced technology so I'll have a look at one.  Here's what I bought from Amazon although they're on eBay too (I can't afford the kind of money you spend :D). I'll be hiding it behind the panel and showing only the spindle & knob.
You did good with that purchase,  it's probably a buck version of that buck/boost module I referenced. Somebody put a scope on the device you purchased and it uses pulse width modulation to vary the voltage output.
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #10 on: February 12, 2017, 05:49:02 PM »
Yep, the reviews are good. I did notice the PWM one.  Even if it lasts a year, I won't cry although I do expect better.
« Last Edit: February 12, 2017, 05:50:52 PM by Dougie Brown »
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #11 on: February 14, 2017, 06:04:15 PM »
So the dimmer switch arrived and it works well. Testing concludes 10.5V is the optimum balance between satisfactory brightness and acceptable heat. HOWEVER... it requires a pos & neg input and a pos & neg output. There is no neg feed beside the existing switched pos, so whilst I can create one nearby for the input, I need to run a neg wire from the dimmer switch output to both ceiling lights (each has its own ground).

Who's got experience of running new wires from the central control panel area into the dinette/lounge ceiling? The existing wiring runs above the polystyrene insulation but not directly (it goes to the passenger side over the fridge somewhere by the sounds of it). I could conceivably go through the insulation via aircon ducts but would like some guidance before I take a butcher's knife out.  Thanks.

Dougie.
« Last Edit: February 14, 2017, 06:06:55 PM by Dougie Brown »
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #12 on: February 14, 2017, 07:19:48 PM »
Bummer.  Can you measure the current the lights are drawing? I wonder if you have the air space (heat dissipation) to use a dropping resistor?  You can punch a channel in the ceiling insulation with an electrician's fish stick (hold the jokes.)  :D
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #13 on: February 14, 2017, 08:09:28 PM »
John, I've looked at resistors, zener diodes and the rest, and I'm sticking to the PWM switch which works a treat. Now I know what fish sticks are (thank you), I'll go that route. :)
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Gary RV_Wizard

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #14 on: February 15, 2017, 11:21:55 AM »
A simple rheostat type dimmer wouldn't need a ground side connection like the PWM type, but they waste power. Nor do they play well with leds, fluorescents or anything with a motor.

As I'm sure you know, the ground side in vehicle wiring typically goes to the nearest chassis/frame point, since that is the vehicle ground. Thus it doesn't usually pair with the hot wire. The good news is that you can use any convenient ground wire or frame spot, so I would look around for a way to "fish" a wire to some point that is grounded.
« Last Edit: February 15, 2017, 11:25:47 AM by Gary RVer Emeritus »
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #15 on: February 15, 2017, 11:53:09 AM »
A simple rheostat type dimmer wouldn't need a ground side connection like the PWM type, but they waste power. Nor do they play well with leds, fluorescents or anything with a motor...
Once you know the current draw of the light strips, the desired load voltage then it would be easy to figure out the resistor size and wattage (I^2 R) required. Wouldn't need a pot or rheostat. Say the source voltage was 14, desired load voltage was 10 and current is 5 amps. We need to drop 4 volts. R=E/I or 4/5 - 0.8 ohms. Resistor wattage would be 5^2 x 0.8 - 20 watts. That's a big honkin' resistor and you would probably need to use nichrome wire around a ceramic form for that low of resistance. Bad idea, forget I mentioned it Dougie  ;D. That would be a huge waste of power like you say Gary.

Using a resistor in series with an LED strip light should be fine - there shouldn't be an inductive component. It won't play well with any inductive load as you mentioned. A traditional ballast fluorescent light would be inductive (the transformer) as of course a motor. Thinking out loud...   I might try to breadboard a test using a sine wave for a source voltage with a resistor in series with an inductive load, it would be interesting to see what happens.
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Gary RV_Wizard

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #16 on: February 15, 2017, 12:28:15 PM »
The other problem with a fixed resistance is that the voltage varies if you ever run off battery instead of shore/converter power. You really need a an adjustable dimmer in RV lighting.

Leds are very voltage sensitive, so the range of usable voltage is usually quite narrow and they start blinking or change color as they get near their threshold voltage.  That's why PWM is the way to go with leds. Rheostats (aka pots) often don't have the finesse for subtle voltage variation, but there are surely some available that would be ok.
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #17 on: February 15, 2017, 12:39:11 PM »
John, the conclusion of your line of thought made me lol, just because you sounded the same as me over the last few days.:D "Ah.... so if I.... and then.... oh wait...... DOH".  The current draw on all relevant lights is 4 amps; I tried a 50Watt load resistor in series which I had, but which roasted itself in a few seconds.  Tried it in parallel out of interest and it reduced the voltage to 9.25 which dealt with the LED heat but made them too dim.

So I'm sticking to the PWM "dimmer" which does a nice job (or will once I go fishin'....). Home Depot awaits....
« Last Edit: February 15, 2017, 12:41:34 PM by Dougie Brown »
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Lou Schneider

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #18 on: February 15, 2017, 02:18:01 PM »
So the dimmer switch arrived and it works well. Testing concludes 10.5V is the optimum balance between satisfactory brightness and acceptable heat. HOWEVER... it requires a pos & neg input and a pos & neg output. There is no neg feed beside the existing switched pos, so whilst I can create one nearby for the input, I need to run a neg wire from the dimmer switch output to both ceiling lights (each has its own ground).

Are you sure the dimmer won't work if you only send the positive wire through it, along with grounding the negative?  I.E. let the lights use their existing ground wire?

+ ---------- +               +-------+
Source           Dimmer           Lamp
- ----------- -                -          - -------------- Existing Ground
« Last Edit: February 15, 2017, 02:20:18 PM by Lou Schneider »

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #19 on: February 15, 2017, 06:38:20 PM »
John, the conclusion of your line of thought made me lol, just because you sounded the same as me over the last few days.:D "Ah.... so if I.... and then.... oh wait...... DOH".  The current draw on all relevant lights is 4 amps; I tried a 50Watt load resistor in series which I had, but which roasted itself in a few seconds. ..
Out of curiosity what was the value of the resistor? I'm amazed you smoked a 50 watt resistor.

Thinking about the problem like Lou did, open up the box the circuit board is in and see if in and out negative (or ground) isn't common. I'll bet it is and you can run +12 from the switch to the dimmer input and then +12 out and -12 (or ground) to the LED strips. Somewhere in your light fixture there has to be a ground or negative the old light picked up.

Forgot to comment on Gary's post..
The other problem with a fixed resistance is that the voltage varies if you ever run off battery instead of shore/converter power. You really need a an adjustable dimmer in RV lighting.
Not really, the +12v to the fixtures will vary from 12.6 up to over 14 with the engine running. They will change brightness a little bit but my eyes are so old I can't see much of a difference any longer  :D

Quote
Leds are very voltage sensitive, so the range of usable voltage is usually quite narrow and they start blinking or change color as they get near their threshold voltage
They are sensitive to too much voltage or current and if you look at a voltage/current chart, there's a 'knee' voltage where they will turn on. I have no idea about the razzmatazz blinky multicolored LED strips, never played with them.
« Last Edit: February 15, 2017, 06:47:46 PM by John Canfield »
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #20 on: February 15, 2017, 09:10:17 PM »
Are you sure the dimmer won't work if you only send the positive wire through it, along with grounding the negative?  I.E. let the lights use their existing ground wire?

Yes, it's a PWM, not an actual dimmer, and it requires both pos & neg inputs and outputs to work. First thing I tried when it arrived although I already knew the outcome.

John, the load resistor rating was 6 ohms. I just happened to have it in a drawer.  Regarding ignoring or not minding the brightness variations, I'm (un)fortunately not yet old enough not to care! :o As I mentioned above, the inadequate resistor put out 9.25 volts whilst in parallel which over-dimmed the lights. Subsequent testing with the new "dimmer" showed that 10.5 volts was a satisfactory balance between reducing the heat enough but not reducing the brightness too much. So the issue of boondocking versus shore power voltage fluctuations was important enough for us to go for the dimmer option despite the accompanying difficulties.

Anyways - whilst looking for fish sticks today, I stumbled across a 48"x3/8" flexible drill bit designed for - yep - making routes for electrical cables! It's awesome (and $7.99 -v- $24.99 for the fish stick)!! So, the installation is complete (lots of polystyrene but not too much blood....) and it's sweet. 8) Definitely worth the effort so as always, thanks for all the assistance.

Dougie.
« Last Edit: February 15, 2017, 09:25:52 PM by Dougie Brown »
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Gary RV_Wizard

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #21 on: February 16, 2017, 05:19:42 AM »
Quote
Not really, the +12v to the fixtures will vary from 12.6 up to over 14 with the engine running.

Since batteries discharge, it's more like 11.5v-14.5v, which will produce light anywhere from dull yellow to bright white. Dougie probably won't want to dim it at all if the voltage is much at all under 12.6.  But your mileage may vary...
Gary
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John Canfield

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #22 on: February 16, 2017, 06:26:47 AM »
...Anyways - whilst looking for fish sticks today, I stumbled across a 48"x3/8" flexible drill bit designed for - yep - making routes for electrical cables! It's awesome (and $7.99 -v- $24.99 for the fish stick)!! So, the installation is complete (lots of polystyrene but not too much blood....) and it's sweet. 8) Definitely worth the effort so as always, thanks for all the assistance.
Everytime I see one of those long flexible bits it's all I can do to keep my hand away from grabbing one off the rack. At our old stick house in Florida I watched our alarm installer use one of those in an inside corner and somehow steer it into the attic, I was impressed.

Glad you got 'er done.
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #23 on: February 16, 2017, 09:54:03 AM »
Everytime I see one of those long flexible bits it's all I can do to keep my hand away from grabbing one off the rack.

Life's short enough as it is. Listen to your inner self. Grab it by the price tag. 😂
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Dougie Brown

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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #24 on: February 17, 2017, 08:52:20 PM »
One small irritation now is the high-pitched whine which emanates from the lights, at its loudest about the mid-way setting and disappearing when completely undimmed.  That's the disadvantage of wave modulation.
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Re: Location of ground wire for galley/dinette ceiling lights?
« Reply #25 on: February 18, 2017, 06:19:43 AM »
Try a 470 uf electrolytic cap across the +- on the LED strips.
--John
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