2021 Ram 1500 Classic Express fog and park lights

[HK1837]

Hi all. I asked this in my build thread but may have been missed by most.

I'm fitting a replacement front bar, which has 20W clear LED floods for the parkers and 40W Amber spots for the fog lights.

I have a spare bar with a harnesses in it, so I was going to cut the plugs (two for parkers and one for fog lights) and make up new harnesses so it all plugs into the factory harness.

I did some searching on the site about possible BCM problems with this, and found some possible information in post 28 of this thread below - is this all I will need to do? The two changes Snowblind indicates? Or will I need some resistors as well?

AlphaRex looking for customers with errors

My lights have been installed for a week now and have been error free. I installed HID bulbs so I had to make that change with AlfaOBD. Sent from my iPhone using TapatalkAny pictures of the light output with the hids ? And which hids did you get? Sent from my SM-T387V using Tapatalk

www.ramforum.com

Here is the bar for interest's sake. The light bar is being done with a relay with the coil driven off the LH headlamp high beam wire.

 

[Wild one]

Hi all. I asked this in my build thread but may have been missed by most.

I'm fitting a replacement front bar, which has 20W clear LED floods for the parkers and 40W Amber spots for the fog lights.

I have a spare bar with a harnesses in it, so I was going to cut the plugs (two for parkers and one for fog lights) and make up new harnesses so it all plugs into the factory harness.

I did some searching on the site about possible BCM problems with this, and found some possible information in post 28 of this thread below - is this all I will need to do? The two changes Snowblind indicates? Or will I need some resistors as well?

AlphaRex looking for customers with errors

My lights have been installed for a week now and have been error free. I installed HID bulbs so I had to make that change with AlfaOBD. Sent from my iPhone using TapatalkAny pictures of the light output with the hids ? And which hids did you get? Sent from my SM-T387V using Tapatalk

www.ramforum.com

Here is the bar for interest's sake. The light bar is being done with a relay with the coil driven off the LH headlamp high beam wire.

View attachment 499833

Curious on why you wouldn't run them off individual switches and relays,instead of tying into the trucks harness.In heavy fog,you're usually better off running just the fogs with-out headlights or driving lights.I'd set them up so each added set of lights was on it's own circuit,so you could mix and match what you want on at any given time or under any given circumstance.

 

[HK1837]

Not sure I understand the question? The parkers already have a switch position (in between off and headlights on). The fog lights are turned on and off by pressing the light switch, they come on with parkers only and operate independent of the headlamps. The light bar will be turned on and off with high beam but can also be turned on independently with a new switch inside the cabin.
All I wanted to know is what needs to happen with the BCM if there are any issues with different wattage parkers: 2 x 20W LED rather than 2 x 5W traditional. And 2 x 40W LED fog rather than 2 x 51W halogen.

I also meant to ask, some Rams have extra buttons down below the TOW/HAUL buttons. I assume these are Canbus switches? Anyone know what they operate or how to access what they operate? See image below.

Edit - I found the answer. 4wheelelectronics sell a kit. Contacted them to see if they can make one as they are OOS.

 

[Wild one]

Not sure I understand the question? The parkers already have a switch position (in between off and headlights on). The fog lights are turned on and off by pressing the light switch, they come on with parkers only and operate independent of the headlamps. The light bar will be turned on and off with high beam but can also be turned on independently with a new switch inside the cabin.
All I wanted to know is what needs to happen with the BCM if there are any issues with different wattage parkers: 2 x 20W LED rather than 2 x 5W traditional. And 2 x 40W LED fog rather than 2 x 51W halogen.

I also meant to ask, some Rams have extra buttons down below the TOW/HAUL buttons. I assume these are Canbus switches? Anyone know what they operate or how to access what they operate? See image below.

Edit - I found the answer. 4wheelelectronics sell a kit. Contacted them to see if they can make one as they are OOS.
View attachment 499847

The way you're going about it,you're going to need diodes so you don't back feed the high beam system.Personally i wouldn't even wire them to the trucks system.A simple switch and relay is all you need to have a simple set-up,that won't mess with the trucks headlight system,and doesn't require diodes,but that's me,i'm old and believe in the "Kiss" principle,"keep it simple stupid",lol.

 

[HK1837]

Having a separate switch is fine to disable the light bar, but useless for high beam switch on/off. It needs to come on and off with the high beams hence the relay tapped into the high beam circuit. I still don't see how the high beam circuit can be back-fed though by simply having a small relay hanging off it? The light bar will be off the relay contacts, just the relay coil will be in parallel with the high beam circuit. Is this where you mean I need a diode, ie on the coil?

The parkers and the fog lights are all separate circuits too so there shouldn't be backfeed issues with those, just possible BCM issues with the different lamp loads. I have seen that vendors like Diode Dynamics sell inline modules for LED conversions, those might work?

 

[Wild one]

Having a separate switch is fine to disable the light bar, but useless for high beam switch on/off. It needs to come on and off with the high beams hence the relay tapped into the high beam circuit. I still don't see how the high beam circuit can be back-fed though by simply having a small relay hanging off it? The light bar will be off the relay contacts, just the relay coil will be in parallel with the high beam circuit. Is this where you mean I need a diode, ie on the coil?

The parkers and the fog lights are all separate circuits too so there shouldn't be backfeed issues with those, just possible BCM issues with the different lamp loads. I have seen that vendors like Diode Dynamics sell inline modules for LED conversions, those might work?

Your call,but with the issues these trucks have with the canbus system,i personally wouldn't screw with tapping into the trucks head lights,when a simple switch and relay fed off the battery is all you need.Why are you hung up on tying into the trucks high beams if you're going to run a master over ride switch that'll need a diode,if you want to turn the bar on while your on low beams. I would think if your idea is to run in Australia's outback,you'd want to keep it as simple as possible,can't get anymore simple then a switch and a relay,and you can keep a couple spare relays in the console,lol. Just my opinion though,you do it,the way you want.

 

[HK1837]

I understand your reasoning, and appreciate the help but i'm not going to tap in, just use a HB3 patch lead, like $5-6, to pickup the switch wire for high beam. Little relays come standard with diodes across the coil so hopefully it doesn't screw with the BCM, but easily removed if it does. They only draw about 0.15A at 12V.

I also don't want the lightbar to come on on low beam, only to come on when high beam is on AND the switch inside is on, that is the switch inside disables the light bar not turns it on - high beam is for that. The switch inside is in series with the relay contacts off the high beam. I don't want to have to dip the lights and turn off a switch.

Similarly with the parkers and fog lights, I'm not cutting the harness, just plugging into it. I ordered some Diode Dynamics 9005/9006 canbus anti-flicker modules to try with these. I'm pretty sure these will match the 40W LED fog lights to the truck's 51W HID OK and/or with maybe the help of AlfaOBD to select LED floods. Not sure how I'll do with the 5W parkers updating to 20W LED. I just want these to work as per normal off the vehicle controls.

 

[Wild one]

I understand your reasoning, and appreciate the help but i'm not going to tap in, just use a HB3 patch lead, like $5-6, to pickup the switch wire for high beam. Little relays come standard with diodes across the coil so hopefully it doesn't screw with the BCM, but easily removed if it does. They only draw about 0.15A at 12V.

I also don't want the lightbar to come on on low beam, only to come on when high beam is on AND the switch inside is on, that is the switch inside disables the light bar not turns it on - high beam is for that. The switch inside is in series with the relay contacts off the high beam. I don't want to have to dip the lights and turn off a switch.

Similarly with the parkers and fog lights, I'm not cutting the harness, just plugging into it. I ordered some Diode Dynamics 9005/9006 canbus anti-flicker modules to try with these. I'm pretty sure these will match the 40W LED fog lights to the truck's 51W HID OK and/or with maybe the help of AlfaOBD to select LED floods. Not sure how I'll do with the 5W parkers updating to 20W LED. I just want these to work as per normal off the vehicle controls.

The reason for the diodes across the relay contacts,is to promote longevity of the relays contacts.They minimize the arcing across the contacts when the relay is switched on/off.

 

[HK1837]

The diode is across the coil not the contacts. As far as I am aware it is to stop voltage spikes on the circuit the coil is attached to caused by the coil's field collapse when it is turned off. Here is a copied and pasted example:

 

[Wild one]

The diode is across the coil not the contacts. As far as I am aware it is to stop voltage spikes on the circuit the coil is attached to caused by the coil's field collapse when it is turned off. Here is a copied and pasted example:
View attachment 499916

Years and years ago,back when i was big into slotcars,and building slotcar tracks,i was adding diodes across the coil contacts of the relays to prolong the life of the relays,as it's been a fairly common trick since i can remember,and as you stated it also provides protection from a back fed EMF field,but for the most part it helps prolong the life of the relays on a 12 /24 volt DC circuit.If you really want to capture all the backfed EMF you need to add a capacitor to the drop out side of the coil on the relay,and it'll absorb any stray back fed voltage spike


A diode across the coil provides a very low resistance, controlled path for the coil's current to travel instead of arcing. Since the resistance is low, it will take a while for the current to decrease and the relay will open slower than without the diode.



Yes, there is current with the sudden collapse when power is instantaneously removed, but there is the voltage spike (of reverse polarity); it can be of benefit or detriment, and generally, we want to remove it. Across the two terminals of the coil, magnetic collapse can produce a DC voltage magnitude of nearly 10x that of the applied DC voltage. …A reason why you could mysteriously get shocked while touching connections as a DC relay releases in a simple “12-volt” system.

When a semiconductor controls a relay coil or a solenoid coil, it must be protected from reverse EMF. A diode is best for suppression as it behaves as invisible during coil power-up, but clamps when there is reverse voltage from instant power-down and thus, a duration of milliseconds of current is contained. The clamp voltage is less than 1 volt as it can’t go for a wild excursion and the control transistor is saved and is protected from the detriment of the spike of death.

Sometimes, a diode-suppressed coil can still upset adjacent digital circuits or cause an audible pop in audio; a diode & capacitor can be useful to reduce EMI noise emission from relay or solenoid switching.

So what are examples of non-suppressed coils? Millions of horn relays and starter solenoid relays in cars from decades of pre-computer automotive production. No diodes used here. With non-suppressed coils, switch contacts exhibit a bit of sizzle and spark when released. That can slowly erode the metal contacts.

Benefit? The sizzle & spark can revive oxidized contacts; performance will improve with repeated operation but these contacts can’t live forever.

 

[HK1837]

Well so far so good. I connected a relay coil (with inbuilt diode, 68032 as per post 9) across the RH side headlight high beam circuit. Haven't got the bar and light bar on yet but the truck has no issue (so far) with the coil across that circuit. The light bar will come straight off the battery via a fuse and the relay contacts so will have no impact on the high beam circuit.

 

[crazykid1994]

I ran my grill backlighting off a relay tapped off the park lights with no issues. Used an automotive fused relay and deutch connectors. Ran my fog lights directly off the factory fog wiring. Only thing is be aware the factory wattage. I’m running diode dynamics ss3 sae/dot yellow fog pro. They are 36 watts. The factory bulb is 55 watts. Had no issues with the truck throwing light out messages and I have no resistors. My step lights are wired directly into the cab footwell lighting but I’m running a very low wattage led tape light. I think it was 3w/ft so 15 watts per side. Only thing I needed resistors for was my switchbacks I put in the front turn signals for a white park light. It only throws a light out message on the turn because of the reduced draw from the park light dropout with the switchbacks. I installed a 20w resistor.

 

[HK1837]

Thanks for the help. My fog lights are 51W and the bar's LED fogs are 40W so hopefully that will be OK. The one I think I'll have trouble with is replacing the 5W parking lights (in the fog lights) with 20W cubes on the bar. Whee did you add 20W resistors in the circuit?

 

[crazykid1994]

Thanks for the help. My fog lights are 51W and the bar's LED fogs are 40W so hopefully that will be OK. The one I think I'll have trouble with is replacing the 5W parking lights (in the fog lights) with 20W cubes on the bar. Whee did you add 20W resistors in the circuit?

At the actual headlight in the headlight wire harness.

 

[HK1837]

In series with or across the headlight?

 

[crazykid1994]

In series with or across the headlight?

Parallel to the turn signal. I had to figure out which wire was the turn signal. The ground is the only black in the set of 3 to the turn signal bulb so that’s easy. You won’t need the resistor if you use a standard amber 3157 led because the park light and turn signal both stay on when you Use the turn signal. The switchback has the dropout feature which cuts the wattage down and that’s what sets the truck off.

 

[HK1837]

Cool, thank you.