2020 px3 Ranger fx4 Left high beam turning of when lightbar piggybacked onto it.

[FX4owner2020]

Hey team looking for advice or if people have had similar issues when piggybacking a lightbar onto their highbeam. This is on my 2020 px3 ranger fx4.
I'm using a stedi smart harness which is also connected to a stedi 8 pin piggyback adapter which is plugged into the Left side factory LED highbeam.
Is supposed to activate the lightbar when using the highbeams however when I use the switch whilst in highbeams the L highbeam shuts off, no fault showing on the dash.

When I switch the lightbar switch off then also switch the highbeams off then on both highbeams work.

Any advice or discussion would be much appreciated.

Cheers

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[airline tech]

The BCM is triggering (FET) protection of the circuit, no fault lights will appear on the dash but if you scan for codes using a scan tool or Forscan you would see High Beam circuit codes.

The lighting output circuits from the BCM are monitored internally by the BCM and it's killing the power when both lights are sharing the power. the High Beam Bulb is about 60 Watts and usually you have a small variance (window) of about 5 Watts, your lightbar I image exceeds that also note that the LEFT and RIGHT lighting circuits are separate runs from the BCM.

You can add a relay and use the (High-Beam) power as the trigger for the relay but the actual power feed for the lightbar must be from another source (Battery) or a separate fused source
or
wire the switch separately and get off the High-Beam circuit

The bottom line is - too much current draw for the (Left High Beam) circuit to have both lights

 

[FX4owner2020]

Hey man thanks for the reply, I have the stedi smart harness which has a relay and a trigger switch to the piggyback, would that still trigger the BCM to cut power to the High Beam?.
Apologies for my lack of knowledge.

These are the harness, piggyback and harness that im using.

https://www.stedi.com.au/plug-and-p...__3Ua3eZGHBxNTFNlU8NSp7ha5Ieq7lbkXx9nbRxwcw2m

https://www.stedi.com.au/ford-ranger-raptor-everest-piggy-back-adapter.html

 

[airline tech]

Since I cannot find or locate any install instructions for the harness, I have to assume that the relay is powered (externally) from the (High-Beam) and if that is the case then

I think I see what's happening - The (Included) relay is back feeding into the (High-Beam) circuit when the Lightbar is powered. The BCM picks it up and shuts down the light driver,

The smart harness is allowing a small amount of voltage to feed back into the high-beam circuit, and the BCM detects that reverse voltage as an abnormal condition and electronically shuts down the left high-beam output to protect itself.

The Stedi harness is designed for vehicles where the high beam circuit is protected by a traditional fuse, but the Ranger's high beam circuit is controlled and protected by the BCM and the BCM monitors that circuit for any voltage anomalies and instead of blowing an independent fuse it disables the power feed

If this is wired the same as the US Version Ranger's, there are (2-Fuses) that feed into the BCM for lighting outputs - Fuse 62 (All LH Side Lighting) and Fuse 67 (All RH Side Lighting) and they are 50-Amp fuses and internally inside the BCM the power is distributed to each light source separately with a (circuit monitor) for each known as the FET - Field Effect Trans Transistor, which is basically a electronic circuit breaker

The relay stays energized because once the high beam initially triggers it, the relay is powered by its own fused battery feed, so even though the BCM shuts down the headlamp output, the light bar continues receiving power independently.

The proposed fix:
The fix is to install a (Diode 3 to 5 amp) in line with the trigger wire from the (High-Beam) feed (Between the T-Connector and the Relay) this will block any back feed of power into the BCM
The Diode will have an (arrow >) on it - install the diode so the arrow is pointing towards the relay
The trigger wire should be feeding (Pin #86) at the relay (referencing the harness pic you posted)

 

[tentspast]

I had this setup with my PX3, and it worked perfectly. Have you reached out to Stedi? possibly a faulty adaptor?

 

[FX4owner2020]

Yeah I have they sent me a new piggyback adapter under warranty and it behaves the same way, they didn't seem to think it was anything to do with the smart harness.

 

[airline tech]

A few confirmations

What is the total wattage of the Lightbar?

Since there are variations on (Connector) pinouts at the headlights (ROW-Rangers) have you confirmed that the Internal (Pinout) of the harness matches the factory (Pinout)?

Is the adapter you are using (Specific) to the Ranger, since the link provided is a dead link, it appears to be correct - but you have LED lights and the harness adapter may be wired for Halogen, and the pins may not be matching (Pin to Pin)

Is the harness long enough to try the RH (High-Beam)? to see if the same result follows as the RH side may not be as sensitive

Can you post how you have everything wired - for verification its wired correctly and also ensure both of the Harness Connections (Power & Ground) are good and clean as well as the Lightbar (Ground)

I know this is labeled as a (Smart Harness), but I think that the issue is when the relay closes (when you flip the rocker switch) you are getting a back feed of voltage into the BCM this is where the Diode will help (it will block that from happening) I think this is the best option as you are not splicing into any factory wiring (only the adapter harness)

You also have the option (via Forscan) to disable the light outage monitoring for the High Beams (it's just an option) I personally do not recommend it

 

[FX4owner2020]

Hey, so the lightbar is 240 W total; the adapter has been confirmed by the manufacturer to work with the LED headlights; the harness isn't long enough to try the RH headlight (I could buy an extension, as they do make them).

I have wired it as below:

*The positive wire connected to the battery pos also has a 60A fuse, which I have checked, and its not blown.
*negative wire to vehicle earth next to battery (initially, when first installed, I had it on battery neg, which produced the same symptoms).
*Harness output connected to lightbar via Deutsch plug.
*The second harness output isn't plugged into anything. I'm told that shouldn't affect anything; however, I'm not sure.
*The trigger wire is connected to the headlight piggyback adapter.

 

[airline tech]

Knowing how finicky the BCM is when tapping into lighting sources I actually suspect it does not like the secondary light source (even as a relay trigger) and you have 3 options

1. Add a Diode (Inline) between the (High Beam) Trigger and the Stedi (Relay),
This will eliminate any back fed voltage into the BCM

2. For a better option, add a (Isolation Relay)
Wire it:
Pin 86: (High Beam Trigger --Diode --Pin 86
Pin 85: Chassis Ground
Pin 30: Tied into the (Fused - Stedi Positive Cable)
Pin 87: Trigger feed for the Stedi Adapter (Relay-Pin 86)

This option gives you a (Clean & Stable) power switch when the relay closes and it's not seeing a (fast high current draw) on the Isolation Relay like it currently is (with the Stedi-Relay)

3. Move off of the (High Beam) as a trigger and use a (Switched Power) source

The sensitivity of the BCM (lighting circuit) is what is triggering the issue, if you intend on using the High Beam circuit, then you need to (add) something to the (Smart Harness) to help block the BCM from seeing it as a problem circuit, so that's what Option 1 or 2 may or may not help, but it's the most logical ideas I can think of as a (cure) for the issue you have


To Test if my theory is accurate - you can verify what is happening by the following tests

See if the STEDI harness is feeding voltage back when the high beams are off.
Using a Meter

1. Stedi-Adapter (Plugged In)
2. High Beams (Off)
3. Back-Probe (High-Beam) Trigger Wire
4. KOER - Key - On Engine Running
5. Measure the Voltage to (Body Ground)

Should read (0-Volts) anything above (0.3 volts) indicates back feed


If you get any voltage reading - do the same test with the (Stedi Adapter) disconnected
and note if the (Voltage Reading) dropped to zero


Now check the circuit at the (Time of the event)
The meter may not be quick enough to see the (voltage) spike but a Scope will catch it

1. Stedi-Adapter (Plugged In)
2. Back-Probe (High-Beam) Trigger Wire -Red Lead and (Black Lead to Ground)
3. KOER - Key - On Engine Running
4. High Beams (On) - note voltage reading
5. Lightbar (On) - note for a quick voltage (drop or spike or bounce) before it drops off
Normal would be (0.0 to 0.2) volts for the relay coil

TIP: If your meter has a (Min / Max) function use it to catch the voltage anomaly


Voltage Decay (Test)
Test with (Stedi Adapter) plugged in and unplugged

1. Back -Probe - (High Beam) Trigger
2. High beams - ON
3. High beams -OFF

Watch how fast the voltage drops to (zero) and note if it takes longer with the (Stedi Adapter)


Optional:
Use an Amp Clamp on the (High Beam) trigger wire to measure the current instead of measuring for voltage
or
Connect meter (In-series) DC-Amps (10-Amp) port
1. Disconnect the (Harness Tap)
2. Red Lead - To the (Truck Side) T-Harness (High Beam-Trigger)
3. Black Lead- To the (Stedi Adapter) (High-Beam - Trigger)
4. While watching the meter
5. Turn on (High Beam)
6. Turn on (Lightbar)

Note: the amperage current differences when the Lightbar is turned on
You're looking for (Under 0.25 to 0.30 amps)

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