Dimmer Switch Replacement

[Converterjoe]

I'm upgrading my 2002 Signature's G-4 halogen lights to LED.  Purchased dimmer switches that are LED compatible to replace the originals.  The new dimmer switches have 12V in (+ and -) and Out to Lights (+ and -).  However, the existing dimmer switch has only 3 connections.  In (+); Ground (1); and Lights.  I'm assuming that the single common ground is fine.  Here is what I don't understand:

With the dimmer switch in the off position, using a multi-meter with the positive lead to "In" and the negative lead to the common "Ground" it registers 12v as expected.  With the positive lead to "Lights" and the negative lead to the common "Ground" it also registers 12v.  Why is the output hot when the switch is in the off position???  It operates the halogens as expected.  What am I missing?  

Thanks in advance for any help.

UPDATE:  For clarification, I'm adding pictures of the switches I'm attempting to swap.  I'm clueless how to proceed.  The original switch has 2 wires each on the GND and +12V lugs.

Edited December 30, 2020 by Converterjoe
Add pics and clarify problem.

[Bill Morgan]

Perhaps the dimmer operates on the Negative side? Remember there is no "ground" in DC, just positive and negative.

 

[Harvey Babb]

Conventional dimmer switches supply power to two circuits. One circuit supplies the high beam bulbs, the other circuit the low beam bulbs. The two sets of bulbs are not usually active at the same time. The common terminal of the dimmer switch comes from power, one of the remaining terminals powers the high beams the other powers the low beams. There is no ground terminal.

I do not know how LED systems work but it sounds like both positive and negative are switched.  I would use the original dimmer switch to operate relays to switch the LED circuits.

 

 

[Converterjoe]

22 minutes ago, Harvey Babb said:

Conventional dimmer switches supply power to two circuits. One circuit supplies the high beam bulbs, the other circuit the low beam bulbs. The two sets of bulbs are not usually active at the same time. The common terminal of the dimmer switch comes from power, one of the remaining terminals powers the high beams the other powers the low beams. There is no ground terminal.

I do not know how LED systems work but it sounds like both positive and negative are switched.  I would use the original dimmer switch to operate relays to switch the LED circuits.

 

 

Thanks, Harvey, but for this project I'm replacing the halogen bulbs in the overhead puck lights in the living areas, not the headlights, although a headlight upgrade is also on the list.

[Harvey Babb]

Oops! That's what happens when I responded before  being fully awake.

 

[Hypoxia]

On 12/27/2020 at 5:54 PM, Converterjoe said:

I'm upgrading my 2002 Signature's G-4 halogen lights to LED.  Purchased dimmer switches that are LED compatible to replace the originals.  The new dimmer switches have 12V in (+ and -) and Out to Lights (+ and -).  However, the existing dimmer switch has only 3 connections.  In (+); Ground (1); and Lights.  I'm assuming that the single common ground is fine.  Here is what I don't understand:

With the dimmer switch in the off position, using a multi-meter with the positive lead to "In" and the negative lead to the common "Ground" it registers 12v as expected.  With the positive lead to "Lights" and the negative lead to the common "Ground" it also registers 12v.  Why is the output hot when the switch is in the off position???  It operates the halogens as expected.  What am I missing?  

Thanks in advance for any help.

Did that year have Multiplex lighting?

[Converterjoe]

Jim C - I don't see any mention of Multiplex in the manual.  I'll Google it.

[Guest Ray Davis]

4 hours ago, Converterjoe said:

Thanks, Harvey, but for this project I'm replacing the halogen bulbs in the overhead puck lights in the living areas, not the headlights, although a headlight upgrade is also on the list.

 

4 hours ago, Harvey Babb said:

Oops! That's what happens when I responded before  being fully awake.

 

I think G4 was the clue that it wasn't headlights but I missed it too.  I thought he was working on the headlights also.

The second wire on the ground is probably going to the next light supplying it's ground connection.  In other words the grounds are daisy chained.

Edited December 29, 2020 by Ray Davis

[Harvey Babb]

OK, not seeing any pictures but I understand the original hardware involved now.

Your original dimmer is electronic and, as is not at all unusual, has a very small amount of leakage current in the "Off" position. Electronic multimeters place an extremely light load on the circuit being measured and so the tiny leakage is still enough to read 12 volts. If connected to a real load (like an incandescent bulb) the voltage will drop to (very nearly) zero so it works as expected when in use. That will explain the confusing readings you are getting.

Get me some more information on the new lights/dimmers and let's see where that leads. 

 

[Converterjoe]

15 hours ago, Harvey Babb said:

OK, not seeing any pictures but I understand the original hardware involved now.

Your original dimmer is electronic and, as is not at all unusual, has a very small amount of leakage current in the "Off" position. Electronic multimeters place an extremely light load on the circuit being measured and so the tiny leakage is still enough to read 12 volts. If connected to a real load (like an incandescent bulb) the voltage will drop to (very nearly) zero so it works as expected when in use. That will explain the confusing readings you are getting.

Get me some more information on the new lights/dimmers and let's see where that leads. 

 

I'm not sure why the pictures didn't upload.  I'll try again.

[wamcneil]

Here’s an article explaining the various types of 12v dimmer. 
http://www.rv-project.com/gear/dimmers2.php

When I replaced the halogen lights, the dimmer circuits flickered horribly. And I couldn’t find a direct replacement for the 3-wire dimmer. Without easy access to the lamp wiring inside the panels, it wasn’t practical to change the configuration to suit a new dimmer. So I went through several LED bulbs before finding some that work acceptably with the old dimmer. I still get a little flicker at very low level, but otherwise works great. 
I also found that if I left one halogen in the circuit, so it might with to put a resistor in parallel with the load to smooth the output.

Cheers

Walter

[Converterjoe]

3 hours ago, wamcneil said:

Here’s an article explaining the various types of 12v dimmer. 
http://www.rv-project.com/gear/dimmers2.php

When I replaced the halogen lights, the dimmer circuits flickered horribly. And I couldn’t find a direct replacement for the 3-wire dimmer. Without easy access to the lamp wiring inside the panels, it wasn’t practical to change the configuration to suit a new dimmer. So I went through several LED bulbs before finding some that work acceptably with the old dimmer. I still get a little flicker at very low level, but otherwise works great. 
I also found that if I left one halogen in the circuit, so it might with to put a resistor in parallel with the load to smooth the output.

Cheers

Walter

Thanks, Walter; now my brain hurts lol 🤣 !  In looking at those diagrams and the pics of my existing dimmer, it would appear that I have a lo-side dimmer but I'm not going to wire anything until I can verify this.  I'm also wondering how difficult it will be to convert the wiring for my lo-side dimmers (if that is indeed what they are) to become hi-side?  

[Converterjoe]

Not sure why I didn't think of this first, but I did a Google search on the old switch (Module #9040 AEC) and found everything I needed to know.  That switch is indeed a low-side dimmer (thank you, Walter, for that illumination [pun intended]) and has been replaced by American Technology part number AH-SLD-5-LS01.  I verified with the manufacturer that it has the circuitry for properly dimming LEDs and that it should mount right where the old switches are, even though they look completely different.  I'll update with some before and afters when they arrive.  Happy New Year y'all!

[wamcneil]

Now that you've placed the order... Here's a 3-wire rotary dimmer that might fit in your existing trim panel.

Amazon.com: 12 Volt DC Dimmer for LED, Halogen, Incandescent - RV, Auto, Truck, Marine, and Strip Lighting - Short Shaft - Black: Automotive

I looked at these back when I upgraded the lights and they were a lot more expensive... so I elected to experiment with the bulbs instead. 

[Converterjoe]

7 hours ago, wamcneil said:

Now that you've placed the order... Here's a 3-wire rotary dimmer that might fit in your existing trim panel.

Amazon.com: 12 Volt DC Dimmer for LED, Halogen, Incandescent - RV, Auto, Truck, Marine, and Strip Lighting - Short Shaft - Black: Automotive

I looked at these back when I upgraded the lights and they were a lot more expensive... so I elected to experiment with the bulbs instead. 

I saw these but I'm not sure if they'll work in a low-side dimmer circuit.  I ordered the American Technology ones which are a direct upgrade from the existing switch for the same ($29.95 each) price from NW RV Supply.  Oddly enough, that's $13 each cheaper than ordering them directly from the manufacturer.  Here's a pic of the new switches.  They'll fit right into the existing holes and wiring will be very plug-n-play simple.

[hitechpete]

On 12/28/2020 at 5:22 PM, Bill Morgan said:

Perhaps the dimmer operates on the Negative side? Remember there is no "ground" in DC, just positive and negative.

 

Usually the ground is negative.