jbplock
10-31-2004, 04:02
There are several well documented methods to implement an All-Headlights-ON modification (i.e. JK Harness, diodes at BCM output, etc..) and here is yet another one… :eek: :rolleyes:
The Helms manual shows both DIMMER-SWITCH (DS) and FLASH-TO-PASS (FTP) circuits are activated by grounding their respective BCM (Body Control Module) inputs. Pulling back the turn signal lever actives the momentary FLASH-TO-PASS switch and applies a ground to FTP input, which in turn activates all 4 headlamps. Pushing the turn signal level forward activates the high beam switch and applies a ground to the BCM DS input. Seeing these features of the BCM inputs, the thought was to use the High beam position of the Dimmer switch to activate – ground – the FTP input. So, yesterday while my neighbors were raking leaves (which I probably should have been doing), I took some time and installed the Fast-Idle mod and tried this FTP headlight mod…. Both worked… (Special thanks to mdrag and modified for the great Fast-Idle instructions).
On my 2003 2500HD the DS and FTP wires are located on two separate BCM connectors. THE BCM is located directly below the steering wheel under the dash. To access the connectors, remove the black plastic air duct and strip back some tape on the wire harness. The DS input is Pin B9 with a Light Green wire on the BROWN C3 Connector. The FTP input is Pin A2 with a Yellow wire on the BLUE C4 connector. To access these wires disconnect both battery ground cables and remove the BCM connectors. The pin numbers are labeled on the back of the connectors. Each connector has more than one yellow and green wire so it’s important to remove the connector to get the correct pin/wire. Once the connectors were removed I used an Ohmmeter to verify the DS and FTP switches by looking for continuity to ground when the switches were activated. The simplest way to implement this mod is to cut the green (DS) and yellow (FTP) wires, then connect the green wire coming from the DS switch to the yellow wire going to the FTP input on the Blue C4 connector. I added a SPDT switch so that the High/Low beam operation could be set back to the OE configuration. The following links show a schematic and installation pictures.
Schematic (http://community.webshots.com/photo/63497470/208208065GeYZJI)
BCM C3 and C4 Connectors (http://community.webshots.com/photo/63497470/208207906OONlLD)
Switch Wired (http://community.webshots.com/photo/63497470/208208311ZkGUWW)
Switch Installed (http://community.webshots.com/photo/63497470/208208148XhriMc)
While this method is relatively simple, there are two disadvantages. 1) It disables the momentary FTP feature on the turn-signal lever. 2) Since the FTP circuit is ALWAYS active, shutting down with the Dimmer Switch in the High-Beam position WON’T shut off the headlights – you have to switch to the Low-Beam Position. If the secondary SPDT switch is added it can be used to return to the OE configuration. A DPDT switch could also be wired to switch both High/Low beam and FTP functions back to stock configuration.
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On edit, since the FTP switch and the High Beam switch can never be on at the same time it's not necessary to break the cut the yellow FTP wire and break the FTP switch connection. The FTP can still function as normal… I plan to reconnect mine when I get a little time to tinker I’ll also update the schematic as well … There are times when I miss having the FTP working. smile.gif
[ 12-31-2004, 05:27 AM: Message edited by: jbplock ]
The Helms manual shows both DIMMER-SWITCH (DS) and FLASH-TO-PASS (FTP) circuits are activated by grounding their respective BCM (Body Control Module) inputs. Pulling back the turn signal lever actives the momentary FLASH-TO-PASS switch and applies a ground to FTP input, which in turn activates all 4 headlamps. Pushing the turn signal level forward activates the high beam switch and applies a ground to the BCM DS input. Seeing these features of the BCM inputs, the thought was to use the High beam position of the Dimmer switch to activate – ground – the FTP input. So, yesterday while my neighbors were raking leaves (which I probably should have been doing), I took some time and installed the Fast-Idle mod and tried this FTP headlight mod…. Both worked… (Special thanks to mdrag and modified for the great Fast-Idle instructions).
On my 2003 2500HD the DS and FTP wires are located on two separate BCM connectors. THE BCM is located directly below the steering wheel under the dash. To access the connectors, remove the black plastic air duct and strip back some tape on the wire harness. The DS input is Pin B9 with a Light Green wire on the BROWN C3 Connector. The FTP input is Pin A2 with a Yellow wire on the BLUE C4 connector. To access these wires disconnect both battery ground cables and remove the BCM connectors. The pin numbers are labeled on the back of the connectors. Each connector has more than one yellow and green wire so it’s important to remove the connector to get the correct pin/wire. Once the connectors were removed I used an Ohmmeter to verify the DS and FTP switches by looking for continuity to ground when the switches were activated. The simplest way to implement this mod is to cut the green (DS) and yellow (FTP) wires, then connect the green wire coming from the DS switch to the yellow wire going to the FTP input on the Blue C4 connector. I added a SPDT switch so that the High/Low beam operation could be set back to the OE configuration. The following links show a schematic and installation pictures.
Schematic (http://community.webshots.com/photo/63497470/208208065GeYZJI)
BCM C3 and C4 Connectors (http://community.webshots.com/photo/63497470/208207906OONlLD)
Switch Wired (http://community.webshots.com/photo/63497470/208208311ZkGUWW)
Switch Installed (http://community.webshots.com/photo/63497470/208208148XhriMc)
While this method is relatively simple, there are two disadvantages. 1) It disables the momentary FTP feature on the turn-signal lever. 2) Since the FTP circuit is ALWAYS active, shutting down with the Dimmer Switch in the High-Beam position WON’T shut off the headlights – you have to switch to the Low-Beam Position. If the secondary SPDT switch is added it can be used to return to the OE configuration. A DPDT switch could also be wired to switch both High/Low beam and FTP functions back to stock configuration.
-----------------------------------------------
On edit, since the FTP switch and the High Beam switch can never be on at the same time it's not necessary to break the cut the yellow FTP wire and break the FTP switch connection. The FTP can still function as normal… I plan to reconnect mine when I get a little time to tinker I’ll also update the schematic as well … There are times when I miss having the FTP working. smile.gif
[ 12-31-2004, 05:27 AM: Message edited by: jbplock ]