dudeman2009
Senior Member
- Joined
- Feb 9, 2016
- Posts
- 1,562
- Reaction score
- 208
- Location
- Arizona
- Ram Year
- 2001 1500 Sport with enough electrical modifications to make my brain hurt
- Engine
- Magnum 360
I had this problem myself, and noticed a few threads on here about it as well. It has to do with the way Dodge setup our lighting system. Unlike most every other vehicle manufacturer out there, they decided to use a positive ground setup on the bulbs, so everything is backwards from what any line of traditional thinking would have you believe. This is compounded by the lighting system being only partially positively grounded, the switch grounds are negative grounds but the bulbs are positive ground.
It took me a little while to figure out how to fix it back to factory with minimal alterations. I personally don't like the jumper method of tying in the fog lamps. Some common symptoms are dash indicator is always lit, the fog lamps won't turn on unless the high beams are also on, or the high beams won't turn on unless the fog lamps are on. On sport trucks with the quad high beams, it is also possible that any time you turn on your low beams your quad lamp high beams also come on and do not turn off, this may or may not prevent the operation of the fog lamps.
After figuring out why the problems were occurring and doing some math, i've figured and tested the solution to be installing a 10ohm 50W or greater wire wound resistor (50W suitable for install in engine bay, 100W required for southern states or dash install) in parallel with the high beam filament on the outboard lamps for sport trucks, and just on the high beam filament for non-sport trucks. Because wire wound resistors have some inductance by design, it is desirable to install a snubber resistor across the wire wound resistor. Otherwise, small voltage spikes up to about 40V may occur when the high beams are shut off, or spikes of about -32V when the lights are turned off.
There are two locations the resistor can be mounted, either in the engine bay by the lights, or under the dash mounted to the firewall. Contact of the metal case to chassis metal is preferred.
disconnect battery before install.
If installing in the engine bay, mounting on the passenger side is prefered as there is more room to work in. There are multiple options for splicing in the resistor, however my preferred method on wirewound resistors is to use spade connectors or solder. On sport model trucks on the passenger side outboard headlamp (9007) cut the wire back from the connector far enough that both the violet and red/orange wires can reach the terminals on the resistor where it will be mounted (you may need to add wire). On both the vehicle and bulb side, strip the violet and red/orange wires. After stripping the wires, pair wires of the same color and either solder each pair to its own side of the resistor, or put both wires into a butt spade connector. Installation of a 1Kohm .5W resistor across the wire wound resistor can be accomplished by inserting the .5W resistor into both the violet and red/orange spade connectors, or by soldering across the wire wound resistor with the two colored wire pairs. Lastly, strip the violet/white wire on both the vehicle side and bulb side and solder or butt connector in a piece of jumper wire.
Mounting inside the dash is mostly the same except instead of splicing into the violet wire, you will have to supply your own 5A fused battery supply to one side of the wire wound resistor. You are still splicing into the red/orange wire coming from the multi-function switch and a snubber resistor is still desired.
The reason both Bi-HID and LED headlights cause problems is due to the diode bridge used in 95% of all electronic boost converters. This diode bridge allows current to flow from the high beam circuit to ground through the low beam side of the circuit. This current is sourced through the dash indicator light and quad beam relay on sport models. When measured, most will have a forward voltage of about 1.5 to 2V at up to 4W of power. This is enough to not only illuminate the high beam indicator anywhere from dim to bright, but also trigger the quad beam relay. The resistor fixes this problem by providing a low resistance voltage source to the lighting boost converter so power is not drawn through the dash indicator light or quad beam relay. The addition of the power resistor will not cause abnormal operation during low beam use. It will however pass about 22.5W of power during high beam use, this is negligible as it is only passing 1.5A maximum current.
All power and current calculations are based at 15V operating voltage, this was intentional. As all power figures are estimated high, heat production is also estimated high, this means that all components should run in the worst case situations without problems. Resistance values should not be changed, however you can size the wattage of components to your desire, using 100W or 200W wire wound resistors will not cause any more current draw than a 25W resistor so long and the value of 10ohms remains the same.
It took me a little while to figure out how to fix it back to factory with minimal alterations. I personally don't like the jumper method of tying in the fog lamps. Some common symptoms are dash indicator is always lit, the fog lamps won't turn on unless the high beams are also on, or the high beams won't turn on unless the fog lamps are on. On sport trucks with the quad high beams, it is also possible that any time you turn on your low beams your quad lamp high beams also come on and do not turn off, this may or may not prevent the operation of the fog lamps.
After figuring out why the problems were occurring and doing some math, i've figured and tested the solution to be installing a 10ohm 50W or greater wire wound resistor (50W suitable for install in engine bay, 100W required for southern states or dash install) in parallel with the high beam filament on the outboard lamps for sport trucks, and just on the high beam filament for non-sport trucks. Because wire wound resistors have some inductance by design, it is desirable to install a snubber resistor across the wire wound resistor. Otherwise, small voltage spikes up to about 40V may occur when the high beams are shut off, or spikes of about -32V when the lights are turned off.
There are two locations the resistor can be mounted, either in the engine bay by the lights, or under the dash mounted to the firewall. Contact of the metal case to chassis metal is preferred.
disconnect battery before install.
If installing in the engine bay, mounting on the passenger side is prefered as there is more room to work in. There are multiple options for splicing in the resistor, however my preferred method on wirewound resistors is to use spade connectors or solder. On sport model trucks on the passenger side outboard headlamp (9007) cut the wire back from the connector far enough that both the violet and red/orange wires can reach the terminals on the resistor where it will be mounted (you may need to add wire). On both the vehicle and bulb side, strip the violet and red/orange wires. After stripping the wires, pair wires of the same color and either solder each pair to its own side of the resistor, or put both wires into a butt spade connector. Installation of a 1Kohm .5W resistor across the wire wound resistor can be accomplished by inserting the .5W resistor into both the violet and red/orange spade connectors, or by soldering across the wire wound resistor with the two colored wire pairs. Lastly, strip the violet/white wire on both the vehicle side and bulb side and solder or butt connector in a piece of jumper wire.
Mounting inside the dash is mostly the same except instead of splicing into the violet wire, you will have to supply your own 5A fused battery supply to one side of the wire wound resistor. You are still splicing into the red/orange wire coming from the multi-function switch and a snubber resistor is still desired.
The reason both Bi-HID and LED headlights cause problems is due to the diode bridge used in 95% of all electronic boost converters. This diode bridge allows current to flow from the high beam circuit to ground through the low beam side of the circuit. This current is sourced through the dash indicator light and quad beam relay on sport models. When measured, most will have a forward voltage of about 1.5 to 2V at up to 4W of power. This is enough to not only illuminate the high beam indicator anywhere from dim to bright, but also trigger the quad beam relay. The resistor fixes this problem by providing a low resistance voltage source to the lighting boost converter so power is not drawn through the dash indicator light or quad beam relay. The addition of the power resistor will not cause abnormal operation during low beam use. It will however pass about 22.5W of power during high beam use, this is negligible as it is only passing 1.5A maximum current.
All power and current calculations are based at 15V operating voltage, this was intentional. As all power figures are estimated high, heat production is also estimated high, this means that all components should run in the worst case situations without problems. Resistance values should not be changed, however you can size the wattage of components to your desire, using 100W or 200W wire wound resistors will not cause any more current draw than a 25W resistor so long and the value of 10ohms remains the same.
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