 Auxiliary Headlight Relays, Installing H4's |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
  |
| Artfrombama |
 Sep 14 2026, 11:50 AM
Post
#1
|
|
Artfrombama  Group: Members Posts: 482 Joined: 21-January 24 From: One of the chosen few Member No.: 27,870 Region Association: South East States 
 |
I've decided to install a pair of H4 headlights with a little more power (55w low, 100w hi beam).
Will I need an auxiliary relay in addition to the factory one above the fuse block? Thanks! (IMG:style_emoticons/default/pray.gif) |
   |
 
|
| Dave_Darling |
Sep 15 2026, 04:06 AM
Post
#2
|
|
914 Idiot Group: Members Posts: 15,364 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
|
You may not need to, but it's a good idea to. The stock setup runs all of the headlight current through the ignition switch, which does it no favors.
If you set up the relays correctly, you can use the old power wires just as triggers to switch the relays on, and then run battery power (through a fuse!!) to the relay and then from the output of the relay to the bulb. Either one relay for the high beam circuit and one for the low, or if you're ambitious you could do one for each side for each beam... --DD |
|
|
|
| Shivers |
Sep 15 2026, 07:17 AM
Post
#3
|
|
Senior Member Group: Members Posts: 3,589 Joined: 19-October 20 From: La Quinta, CA Member No.: 24,781 Region Association: Southern California |
QUOTE(Artfrombama @ Sep 14 2026, 10:50 AM)  I've decided to install a pair of H4 headlights with a little more power (55w low, 100w hi beam). Will I need an auxiliary relay in addition to the factory one above the fuse block? Thanks! (IMG:style_emoticons/default/pray.gif) I'm doing that now. I really do not like adding to the electrical system. I put in a duel relay and some fused links if I want to add something later, in a box. I ran a #10 wire run from the battery to the relay box inside. Trigger wire inside from the switch will draw an amp or two. I put it inside to protect it. I have a single relay says it is waterproof that goes in the engine compartment for the rear fog light.    |
|
|
|
| anderssj |
Sep 15 2026, 09:38 AM
Post
#4
|
|
Dog is my copilot... Group: Members Posts: 1,801 Joined: 28-January 03 From: VA Member No.: 207 Region Association: MidAtlantic Region
|
There’s a thread here about using the JWest relay kit for early 911s; see second post:
www.914world.com/bbs2/index.php?showtopic=364705 I followed these steps and did the same to my car (‘72). And these relays also play nice with the JWest fog light flasher module. Hope this helps! |
|
|
|
| barefoot |
Sep 15 2026, 11:06 AM
Post
#5
|
|
Senior Member Group: Members Posts: 1,550 Joined: 19-March 13 From: Charleston SC Member No.: 15,673 Region Association: South East States
|
Why not convert to LED bulbs instead, there are the out there that plug into H4 sockets, then don't need more relays & get better lighting.
|
|
|
|
| Jamie |
Sep 15 2026, 11:45 AM
Post
#6
|
|
Senior Member Group: Members Posts: 1,225 Joined: 13-October 04 From: Georgetown,KY Member No.: 2,939 Region Association: South East States
|
QUOTE(barefoot @ Sep 15 2026, 09:06 AM) Why not convert to LED bulbs instead, there are the out there that plug into H4 sockets, then don't need more relays & get better lighting. That's what I did, and better light with less draw on the old wiring system. Plug and play! (IMG:style_emoticons/default/confused24.gif) |
|
|
|
| Artfrombama |
Sep 15 2026, 03:20 PM
Post
#7
|
|
Artfrombama Group: Members Posts: 482 Joined: 21-January 24 From: One of the chosen few Member No.: 27,870 Region Association: South East States
|
QUOTE(Jamie @ Sep 15 2026, 12:45 PM) QUOTE(barefoot @ Sep 15 2026, 09:06 AM) Why not convert to LED bulbs instead, there are the out there that plug into H4 sockets, then don't need more relays & get better lighting. That's what I did, and better light with less draw on the old wiring system. Plug and play! (IMG:style_emoticons/default/confused24.gif) 1. Old fart/old school 2. H4's were a gift 3. Prefer the classic look 4. Serviceable 5. Get off my lawn! |
|
|
|
| Ishley |
Sep 15 2026, 03:36 PM
Post
#8
|
|
Member Group: Members Posts: 366 Joined: 4-October 21 From: Clarendon Hills Il Member No.: 25,957 Region Association: Upper MidWest
|
I installed them without a relay. No issues
|
|
|
|
| Ninja |
Sep 15 2026, 07:06 PM
Post
#9
|
|
Member Group: Members Posts: 311 Joined: 25-September 25 From: Granbury Texas Member No.: 29,004 Region Association: Southwest Region |
Relays always!
Does two things. Saves your fragile 50-year-old switchgear by removing amperage from it. Relays (at least good ones) pull almost nothing. Voltage drop to your load is greatly reduced and "available" voltage at the load is maximized. I am positive that adding a properly wired relay will make even the original light bulbs brighter than they were when new. I upfitted a 73 240Z with H4s, eurospec bulbs, Bosch 40 amp relays (2), 12g wiring and bulb sockets. I reduced the wiring run to the filaments by 15 feet, and sourced power from the alternator power lug. The little fuse/relay pack I made was VERY similar to the previously posted one. Cost me WAY more than $18 to make... Original owner was blow away at how bright his lights were. The lights would MELT snow falling in front of them 10 feet away when stopped. Flame throwers... Old school halogens, done right, Kick ASS! |
|
|
|
| Dave97 |
Sep 15 2026, 08:26 PM
Post
#10
|
|
Member Group: Members Posts: 57 Joined: 25-July 17 From: Calif Member No.: 21,285 Region Association: None |
How about adding the relays next to the fuse box? Put the relay in between the fuse box and the wiring going to the headlights
|
|
|
|
| Artfrombama |
Sep 16 2026, 06:39 AM
Post
#11
|
|
Artfrombama Group: Members Posts: 482 Joined: 21-January 24 From: One of the chosen few Member No.: 27,870 Region Association: South East States
|
QUOTE(Dave97 @ Sep 15 2026, 09:26 PM) How about adding the relays next to the fuse box? Put the relay in between the fuse box and the wiring going to the headlights looking at the wiring schematic, there is a white wire (hi beam) and a yellow wire (low beam) that run from the column switch to the fuses. Looks like an ideal location to add relays, and no wires need to be cut. I would need to run a 10-12ga. batt+ to the auxiliary relays. |
|
|
|
| cdn914 |
Sep 16 2026, 12:31 PM
Post
#12
|
|
cdn914 Group: Members Posts: 209 Joined: 15-March 04 From: Winnipeg, Canada Member No.: 1,801 Region Association: Canada
|
I have used the H4s on my 1970 (914-6) since the mid 1980s and never had a problem.
|
|
|
|
| 914Sixer |
Sep 16 2026, 04:48 PM
Post
#13
|
|
914 Guru Group: Members Posts: 9,570 Joined: 17-January 05 From: San Angelo Texas Member No.: 3,457 Region Association: Southwest Region
|
Read the factory manual instructions. Euro cars came with H4. Does not need extra relay. Click to open page.
Attached thumbnail(s) 
|
|
|
|
| Dave_Darling |
Sep 17 2026, 08:37 PM
Post
#14
|
|
914 Idiot Group: Members Posts: 15,364 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
|
I don't think the factory option H4s were 55W / 100W. That's a bunch more power to be putting through your ignition switch.
It will definitely work in the short term! In the long term? --DD |
|
|
|
| 914Sixer |
Sep 18 2026, 01:57 PM
Post
#15
|
|
914 Guru Group: Members Posts: 9,570 Joined: 17-January 05 From: San Angelo Texas Member No.: 3,457 Region Association: Southwest Region
|
DD, I missed the 100W on high, Factory H4 55/60, my bad.
|
|
|
|
|
2 User(s) are reading this topic (2 Guests and 0 Anonymous Users)
0 Members:
|
Lo-Fi Version | Time is now: 20th September 2026 - 07:19 AM |
Invision Power Board
v9.1.4 © 2026 IPS, Inc.