Wiring car light relays with dimmable switches

Thread Starter

Elliott Balsley

Joined Aug 31, 2016
21
Almost, but the winch switch is still connected too. If the hazard button is on, then pressing the reverse button illuminates both. And the same issue, if the winch switch is on, pressing the reverse button illuminates both.

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Thread Starter

Elliott Balsley

Joined Aug 31, 2016
21
If the winch switch is on and you press the Reverse switch does the winch LED come on also?
SG
Yes. With the reverse button off, the others work correctly. But the problem is the combination of that button with either of the others. I checked the diode with my meter on diode mode and it measures 0.9v in that direction and infinite in the other.
 

mvas

Joined Jun 19, 2017
538
Almost, but the winch switch is still connected too. If the hazard button is on, then pressing the reverse button illuminates both. And the same issue, if the winch switch is on, pressing the reverse button illuminates both.

View attachment 171413
I think, you need a Reverse Blocking Diode in EVERY new switch, including Winch.
I don't see a Reverse Blocking Diode there?
Now, does that fix every everything?

Also the internal Illuminated Diodes are actually in Parallel ( back-to-back ) and
not Series connected as shown in your diagram ( minor point )
 

Thread Starter

Elliott Balsley

Joined Aug 31, 2016
21
If the reverse and hazard buttons are both lit, and I switch the winch on, the hazard buttons gets dimmer and the reverse button gets brighter. This is a clue but I'm confused here.
 

sghioto

Joined Dec 31, 2017
2,363
If the reverse and hazard buttons are both lit, and I switch the winch on, the hazard buttons gets dimmer and the reverse button gets brighter. This is a clue but I'm confused here.
That makes perfect sense if the diode in series with the reverse switch LED is in backwards or defective.
EDIT: What type of diodes are you using?
SG
 
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Thread Starter

Elliott Balsley

Joined Aug 31, 2016
21
I added a diode on the winch switch, that doesn't make any difference.

I reversed the diode on the reverse button but that doesn't make any difference. When my multimeter is in diode mode I always assumed the red lead goes to the anode, but now I'm questioning that.

I had just grabbed some old diodes out of my parts bin, but looking closer I see the one on the reverse button is different. It's a 51B3 and the others are 1N4148. I can't find any datasheet on it. I'm out of 4148 so I replaced it with another unknown glass diode and I still have the same problem but all the buttons are much dimmer. This new diode measures 0.2v. I'll buy some new diodes this week.
 

mvas

Joined Jun 19, 2017
538
Almost, but the winch switch is still connected too. If the hazard button is on, then pressing the reverse button illuminates both. And the same issue, if the winch switch is on, pressing the reverse button illuminates both.

View attachment 171413
Verify that all three diodes are OK
Verify that all three switches ( Reverse, Hazard & Winch ) have a Diode ( 1N4001 ? )
Verify the Polarity of each diode is correct, BAND side points towards Dimmer ( light blue wire )
Verify that all three diodes are connected to exactly same point on the Dimmer.

YES, you do need a Reverse Blocking Diode for the Winch LED - must protect LED from >5 volts Reverse Polarity - it can happen!

The final schematic diagram should work as drawn.

Yes, plus one additional diode in series with the others leading to the dimmer.
Where is this ( 4th ? ) Diode located ?
 

mvas

Joined Jun 19, 2017
538
So with all 1N4148 Diodes, and not any zener diodes, are the Illuminated LED's in the Switches working properly when OFF & ON when?

I still stay ... You need a 1N4148 in the Winch LED circuit, too.
It is possible for your circuit to apply 12 volts Reverse Bias on the that LED and it will blow,
since LED's can only take 5 volts Reverse Bias.
 

Thread Starter

Elliott Balsley

Joined Aug 31, 2016
21
Yep with the new diode everything is working fine. I also added one to the winch switch for safety at your suggestion. Many thanks to both of you for helping figure this out.
I wonder if a simpler solution could have been to apply a high voltage to the button to burn out one of the LEDs, leaving the other intact.
 

mvas

Joined Jun 19, 2017
538
Yep with the new diode everything is working fine. I also added one to the winch switch for safety at your suggestion. Many thanks to both of you for helping figure this out.
I wonder if a simpler solution could have been to apply a high voltage to the button to burn out one of the LEDs, leaving the other intact.
Wahoo !
I doubt that we could blow one LED and not the other LED.
I think, as soon as you blow LED #1 with a "Too High" Forward Voltage, then LED #2 will blow from a "Too High" Reverse Voltage ???
If the Illuminated Switch was a DPST switch then the LED and Load would be separated when switched OFF and
then no Blocking Diode would be needed.
DPST = +12v to both Poles Input then Pole #1 output for the LED & Pole 32 Output for the Load.
Powering BOTH the Illuminated LED & the Load with a simple SPST Switch was the root cause.
 

mvas

Joined Jun 19, 2017
538
Using DPST Illuminated Switches , eliminates the blocking diodes.
Current limiting resistor for Internal LED, not shown.
Power wire from each "FUSE" through Relay N.O. Contact to the Load, not shown.

LED-BAR-3-small.jpg
 
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