Problem installing Sucro headlight relay kit

Russ in VA · 09-13-2005, 05:20 PM

Before anyone says "do a search" I have just burned an hour doing just that to no avail. Either my car is unique OR I am just dense. Please read about my problem and help me figure out which one it is!

Based on the instructions that Marcus provided with the kit, there should be one fuse for low beams and one for high in the factory fuse box that are to be re-routed using his kit.

My '84 Carerra has FOUR headlight fuses: one for left side low beam, one for right side low beam, one for left high and one for right high

Ultimately, it seems that I should really have four relays to keep all these routed separately. Since I want to finish this tonight, I am trying to decide if I should:

A) route one side of the low beams through Marcus's relay and one side high beam through his other relay, leaving the stock wiring for the opposing side and thus reducing the load on the headlight switch to just over half of what it was stock

-or-

B) route both of my low beam wires out of Marcus's single relay and both of my high beams out of Marcus's high beam relay

I'm leaning to option B.

Any suggestions will be appreciated!

Thanks,

Russ

lagrassa · lagrassa's Garage

Given your options, I'd do B. That is eesentaily what is done when there is one fuse per high beam and one fuse per low beam. I have done this to my '70 T and it works great.

Nathans_Dad · Nathans_Dad's Garage

How long did it take to get your kit? I paypal'd him about a week or so ago and haven't heard anything by e-mail...

Russ in VA · 09-13-2005, 05:28 PM

Well, I bought it about a year ago but it seems like I got it pretty quickly. Obviously I was not really in that much of a rush so I might have been a week or two and I would not have noticed!

RoninLB · 09-13-2005, 05:48 PM

if you want the safety of all seperate circuits buy another 2 relays.

jyl · jyl's Garage

I think I did B on my Carrera.

FrayAdjacent911 · 09-13-2005, 06:18 PM

I don't think there'd be any harm in bridging the circuits (connecting both the left and right circuits) , unless the wiring is old, and could overheat.

It would be safer to separate them and use a relay for each side, though. That's probably how I'll wire mine up when I get a round tuit. Probably when I get around to doing the H4 upgrades... but I much much work to do before I get to that point!

RoninLB · 09-13-2005, 06:37 PM

member bell did a nice post on the 4 relay install.

I use only 2 relays and carry a spare relay and bulb.

'78 SC · '78 SC's Garage

Yeah, option B. The fuses are bridged on one side (the side originally wired to the headlight switch), so all the current will flow through the relays, but lights will be individually fused (one fuse per filament).

The current load should not be a problem. Even if you installed 100 W hight beams, the current through the relay would be less than 20 amps (100 W / 12 volt x 2 ). What are the Sucro relays rated for?

deoxford · 09-13-2005, 09:34 PM

Russ,
Can you tell em more about this kit, what it does and were to find it. I think it sound like it will fix my headlight prroblem.

Wil Ferch · 09-14-2005, 01:16 AM

78SC:

OK...so you're up to about 20A with a 100W bulb, but the possible problem won't be with the "cube" style relays...mostly rated at 30A or such..it will be the wire gauge from the fuse box to the headlights. I'm not in front of my notes at the moment, but 100W would be my self-imposed limit with this set up and wire sizes.

To the original poster...you can go with B.) where a input power goes to a pair of headlight fuses ( either low-pair or high-pair as Marcus Sucro suggests in his install write-up). Of course, 4 is better.

For those going with monster wattages...don't just upgrade the power feed wire gauge to the lights...upgrade the return ground wire size too...otherwise you've done less than 1/2 of the job.

Wil

'78 SC · '78 SC's Garage

Wil,

Absolutely, you have to take a whole system view. I don't recall the existing fuse ratings; is the wiring (including grounds and sockets) adequately protected if you stay stock from the panel out?

Wil Ferch · 09-15-2005, 07:06 AM

yep.....

Wil

Joeaksa · 09-15-2005, 08:12 AM

Good thread!

Jadams1 · Jadams1's Garage

Here's another link to a two relay setup wired for 80W/100W H4's.

Headlight Upgrade Pics

DW SD · 09-15-2005, 08:28 AM

Go with option B! That will be fine. Remember, in your stock setup, though you have individual fuses, they all are still switched through the headlight switch, which is what you want to avoid. Two relays absolutely avoids using the headlight for switching larger currents.

Doug

steve911 · steve911's Garage

When I did the Sucro relay install, I also added an inline fuse between the battery and the relays. It was suggested by RoninLB in this thread . He suggested a 25A fuse.

911S Targa · 911S Targa's Garage

I used 4 relays when I did my upgrade to 80/100Watt H4's

Mysterytrain · 09-15-2005, 12:38 PM

Ok, so I'm wondering why not use one 5 pin relay? 87a, the normally closed postion would be the low beams and 87 when energized would be the high beams. You would need to run one wire up to energize the relay, most likely in my case the connection from fuse 8. [which is also the feed for the dash indicator lights. Am I missing something with this method? If the 100 watt bulbs are your max then each headlamp would be drawing about 8 amps..so figure about 16 amps total on the high beam contact (87) and 85 watt low beams would draw collectively about 13 amps on 87a. This is all based on 13.5 volts. After looking at all the old threads on this subject and the pano article I'm also that the power sourced from the battery should be fused before the relay or relays and again on each feed to the bulb filiments..so four fuses on the relay outputs. Ok, smack me around on the one relay method??

RoninLB · 09-15-2005, 04:16 PM

Quote:

Originally posted by Mysterytrain

. Ok, smack me around on the one relay method??

creativity and personalizing is what our cars are about imo.

meanwhile, the normally closed lows would be on all the time, even when parked.

my bright idea was to trigger both high and lows in the Hi switch position. Both filimints overloaded the single common bulb ground.
Both left & right went kaput within 5min of each other. This all happened on a black road with no moon as I was testing my bright idea. Other than the kaput part, both filimints on at the same time seemed pretty nice.