• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Halogen head lights

Share this page

Hello Dave,

I understand what you are saying, but as the main harness to the lighting switch is heavy gauge, a relatively short run and no bullet connectors for the most part. The majority of the voltage loss to the headlights is from the main lighting switch, through the dip switch and out to the front of the car.

Alec
 
And most importantly it does work. Like I mentioned previously, driving Bugsy at night would have been better with that 2 D Cell Flashlight held out the window. Now I actually have other driver's flashing at me to "Dim My [censored] Lights." This is a cheap safety issue that I was able to fix for < $20 and a few hours of time. Oh and make sure you connect the hi beams to the same power wire that connects the hi beam indicator on the dash. Check it all works before doing final soldering, don't ask me how I know.

Oh and it is possible to change that Hi Beam indicator from White to Blue. A blue file folder translucent/page protector sheet and a hole punch along with 3-4 blue dots pushed in from the inside and you've now got a blue hi beam indicator.

Seeing in the dark once again.
 
Alec, the main harness may be somewhat heavy gauge, but when the lights were on there was enough voltage drop to be noticed on the other accessories. Yes the headlights were getting a drop from the headlight switch, dimmer switch, and headlight wiring, but what I'm saying is the main harness had a significant voltage drop, too. If it didn't, then there would have been little or no difference when the lights were on. Instead, when the headlights were on the blower motor ran slower, the wipers ran slower, the rest of the lights were dimmer, and the turn signals would stop blinking. Now that the headlight current is coming through a different path, these problems are gone. The wipers run at the same speed, the blower motor runs at the same speed, the dash lights are brighter, and the rest of the lights don't dim noticeably when switching between the parking lights and headlights.

Maybe there were other issues with bad connections in the wiring harness, but for whatever reason there was a significant amount of resistance in the main harness.
 
Hello Dave,

"Maybe there were other issues with bad connections in the wiring harness, but for whatever reason there was a significant amount of resistance in the main harness.",

what you describe is not typical and you have, I think, answered the problem with your last paragraph. Also, is it possible that you corrected this by disturbing something when you did the modification?

From your nickname I have to assume that you are electrically knowlegeable and understand that voltage in this context is equal to resistance (cross sectional area), current carried and length.

Alec

Alec
 
Hi surely,as the supply to all accessories and lights originates from the same supply wire,this would be similar to me having a shower and when someone turns the hot tap on somewhere else the water went cold,by putting a dedicated feed to the shower ,it doesn't happen now.Same with the dedicated headlamp wiring from source, the current is allowed to flow freely and hence brighter lights,and enough current allowed to flow to the other accessories to keep them happy.
 
OK - I think I'm getting this - forgive me for sounding a little dense. The relay is the switch and I presume that relay switch is actually turned on/off by the original headlight switch?

Therefore

original headlight switch and current from original wiring harness provides current to switch on/off relay which in turn turns on/off headlights which are now wired independently of the original wiring harness presumably lowering the load (draw) of the whole harness.

assuming this is correct, where does the new (headlight) wiring originate? Battery? Fuse box?

thanks again all
 
I came off the battery connection on the regulator and added a new fuseblock.
 
One last question - OK 2

1. I was at the surplus store & they had Bosch 12v relays - I presume the 12v refers to the switch & not the current to the headlights - ie. I could (for whatever reason) run 24v circuit with a 12v switch - right?

2. How do high beams work? Is there an added line?

thanks all
 
Don't know about the relay but think so.

However, there is a high beam wire.
 
12V refers to the nominal voltage needed to close the relay's switch contacts. They're not picky about this--if you system hangs around 14V or droops to 10V, that's just fine. The important thing is the current rating for the contacts. It is extremely important not to exceed this; in fact, I'd leave about 30% margin (e.g., use a 40 amp rated relay to handle up to 30 amps). DC current will fry any kind of switch contacts really fast, if you exceed their rating.

I use Panasonic automotive relays for this kind of thing. They are cheap (like about $4 each) and the contacts are rated at 40 amps, which will handle pretty much anything in a Sprite. You can get them with a mounting tab and 1/4" spade lugs for the electrical connections. They are available from Digi-Key, https://www.digikey.com, and look for part no. 255-1828-ND. I think this is the one I got; unfortunately, there are a whole lot of different ones, each is about 1% different from the other. You can see one in my Sprite in a picture here: https://www.nonlintec.com/sprite/electrical/mods_3252.jpg.

The 40 amp contacts seem to be a de facto standard for automotive relays; other manufacturers make relays to specs virtually identical to the Panasonic ones.

If you're planning to add a headlight relay, it would be a good idea to get a wiring diagram for your car. That will answer a lot of questions.
 
There are 4 wires going to the headlights on the P.S. of the car. Off the top of my head I seem to recall a Blue /White & Blue /Red plus two ground wires.

Fused Power Wire goes to I used solenoid screw as 12VDC Power Source.

Need 2 Fuses, 2 Relays,

Wire fron dimmer switch is the input to the relay when headlight switch is turned on it turns on the relay

That closes the relay to pull power direct from the battery.

This is the Blue/White & Blue Red. This is the control for each relay.

Think of the relay as the switch that turns the headlights on and connect directly to the battery. Since there is a Hi and Low Beam you need two switches and as always a ground wire to complete each circuit.
 
Back
Top