HID relay harness diagram

[TeeShock]

I ordered a replacement ddm kit after my first kit if 3 years failed. The new kit (same wattage) flickers and I don't want to wait for their dinky harness to ship from China so I'm gonna wire one up this weekend. Im going to use my old kit's connectors to build a true pnp dual relay harness and tidy it all up behind the bumper support. Does this look correct? All input is appreciated!

[BERNIE MOSFET]

Any reason for two relays?

[TeeShock]

Any reason for two relays?

When a relay decides to crap out I will still have one headlight. Or should I wire them as 1+1 active redundancy? Or am I overthinking the whole enchilada?

[BERNIE MOSFET]

I don't think the redundancy is a bad idea. I was just curious about whether that drove the design decision.

You could make it an active redundancy, but then you need some indicator that the primary failed. That's probably more work than it would ever be worth.

[TeeShock]

I don't think the redundancy is a bad idea. I was just curious about whether that drove the design decision.

You could make it an active redundancy, but then you need some indicator that the primary failed. That's probably more work than it would ever be worth.

What should I expect to crap out first, the line/load fuses or the cheap autozone relays? I'm trying to prevent having to take it back apart to tinker with it. How would I go about wiring the failure indicator? I like making things complicated.

[shumpertdavid]

The load will be the same on each side of the relay, if the hid only needs a 15 amp fuse, then a single 15 amp fuse near the battery should be sufficient.

[TeeShock]

Im thinking of wiring the diagnostic led light between the load side and the ground on the relay. So if my ballast fuse fails I will still see the led. If the relay fails my led will be off. Typical for both relays. Why would I not fuse between relay and ballast, David?

[BERNIE MOSFET]

Relays will fail first.

If I wanted to make the system more robust,
I might consider a quality DPDT primary
relay that, when energized, relays power to
lights and breaks ground from the
secondary. If the primary fails, failure mode
energizes secondary and the indicator.
Since you are installing this in the bumper,
maybe mount a narrow angle LED so that it
illuminates the ground on condition of
primary relay failure.

Have a look at this. I realize it's oversized, doing this on my phone. Not going to make it smaller.

[BERNIE MOSFET]

LED is backwards. I'm showing the anode grounded.

[TeeShock]

Since I didnt have a DPDT relay on hand and needed to get my headlights operational asap i went ahead and just did a 1+1. I probably wont have the car long enough to see the relays fail. But I want to try that schematic for my kegerator project since the relay and controllers will all be readily accessible. Ill save the details for the build thread. Thanks for your help!

[shumpertdavid]

Why would I not fuse between relay and ballast, David?

The amp load before and after the relay will be about the same. The only reason I could see for having the fuse between the relay and the ballast would be to help you diagnose which side of the system has the problem if one blew.

[TeeShock]

The amp load before and after the relay will be about the same. The only reason I could see for having the fuse between the relay and the ballast would be to help you diagnose which side of the system has the problem if one blew.

I agree fusing at the power source but another concern was if the relay fries is there potential to cause ballast damage?

[BERNIE MOSFET]

Since I didnt have a DPDT relay on hand and needed to get my headlights operational asap i went ahead and just did a 1+1. I probably wont have the car long enough to see the relays fail. But I want to try that schematic for my kegerator project since the relay and controllers will all be readily accessible. Ill save the details for the build thread. Thanks for your help!

Right on. Glad to offer input.

[TeeShock]

Update. Everything has worked fine until Sunday night I stopped for gas and when I re-energized the headlights they didn't come on. This fuse housing is rated to 30 amps and it had a 25 amp fuse in it. Not sure what cause it but I replaced it with the same model and only a 20a fuse. Seems to be okay just thought I'd share

[shumpertdavid]

I would guess that the terminal didn't hold tightly to the fuse blade. High resistance caused heat to build which allowed the terminal to loosen more, and higher resistance and more heat causes the melting. You might take a pair of pliers and tighten up the female terminals on the new fuse holder some die electric grease will also fight off corrosion and moisture damage.