Headlight Assembly Question

I'm dealing with that exact same problem with a Prius I'm working on so I just ordered the halogen bulbs and plugs for them online. Way more reliable way to go than those garbage HID ballasts that fail often and are expensive to replace.

 

The HID lights have a constant (large current) bulb and high or low is just a mechanical shutter that blocks some of the light. The shutter is controlled by a (small current) solenoid via the high beam switch. This solenoid circuit is too small to directly feed a halogen light.

Halogen lights are wired with two separate (large current) feeds- one for low and one for high. It turns either one on when you move the switch.

So you have to use a relay (one per side) that is triggered by the hi beam solenoid circuit to switch the large current power feed between the low and high beam terminals on each halogen bulb.

Search the forum for "HID to halogen conversion" to find the thread that explains everything.

Posted via the PriusChat mobile app.

 

I'm actually just about ready to do this conversion to halogen on a Prius with LID and I'm unclear on the need for a solenoid circuit? There was one guy who simply wired the new plug for halogen bulbs with the wires upstream of LID Ballast and he had no need for anything other than some butt connectors, socket and bulbs? Can you help clarify? I've yet to find a functional link to the additional "hi-low beam switch" as some call it or "solenoid" as you call it. So not sure what to buy, or if it's even necessary?

 

I was passing on info from a post (#20) I had come across here:How to convert from hid to halogen | PriusChat
This could make sense to do that way to limit heat build up in wiring connections or the headlight itself. However...

Since you mentioned it I looked at the wiring diagram and I am not sure now that the relays are needed. The HID lights turn on and when you move the turn signal lever to change "high" or "low" beam the combination switch (aka the hi-low beam switch) sends a signal to the BCM, which in turn triggers the "Dip" relay. That relay sends power to a "shade actuator" or shutter "solenoid" on each headlight assembly- the shade just moves to allow more or less light to shine out on the road- that's how you get a "low" beam or "high". (the halogen bulbs have two separate filaments to accomplish that) I had assumed that the circuit for the shade actuator wasn't able to supply enough power for the high beam filament on a halogen bulb, but apparently it is (or should be). At least the diagram shows the same circuits were used for both types of lighting. I had also assumed that the factory halogen used one filament for low beam OR the second for high, but apparently it uses BOTH for high.

So yeah, it looks like you could just remove the HID's and wire in the halogens- that's it, no additional parts.

 

Thanks for that... Been procrastinating on that one...