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Headlight relay question

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budk1953

budk1953

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I've been trying to figure out the proper relays to use for headlights (without buying an expensive kit) and the more I read the more I get confused.
30 amp or 30 amp with load open (40 amp)?
4 pin or 5 pin?
With diode or without diode?
SPST or SPDT?

And what would be used in other applications - horn, brake lights, cooling fan, etc.?

I've attached a link to a site that sells relays if it helps...
Relays

Thanks,
Bud
 
A SPDT will have other terminals to make parallel and isolated connections. You will need two SPDT relays. No diode is required.
 
Bud,

Think of it this way, one relay for the low beams and one for the high beams. On Bugsy my '68 Sprite I use a 30 amp fuse in an in line fuse holder for each relay connected to a lug I bolted down to the battery cable running directly to the solenoid. I mounted the relays approx where the MC would be if this was a RHD Car. It's a simple connection to the I believe Blue White and Blue Red wires that come out of the harness and go down to the headlights. Both the Hi and Low Beam share a common ground wire, Green I believe. Someone please correct me if my memory is fuzzy on those wiring colors.

Tip, before all is soldered and mounted and heat shrinked together. Make sure the Hi Beam indicator comes on with the high beams. Don't ask me about needing to take it all back apart after I had all fixed nice and neat. Don't forget to zip tie it all together as well to keep wiring neat and secure. Trevor showed me some nice black wire loom wrap cloth available from JEGS that really neatens up everything when you have it all working together.

A soldering iron, heat shrink, and a little cogitation and it will all come together.
 
Visit the Advance Auto Wire site. (Formerly owned by the family of Dan Masters who posts on this board).
https://www.advanceautowire.com/

On the left side of the screen you'll see a link for "Headlight Relay Kit". Click on that link to see what they offer in kit form. They have been kind enough to show their schematic on the page. If you decide to make your own relay board, their schematic is elaborate enough to show the terminal numbers on the relays. The relay terminal numbers are consistent with those used on the common ISO/Bosch 30 Amp relays you can buy in parts stores... or from places like:
www.bgmicro.com
(search using keyword "bosch" to find relays and sockets).
or
https://order.waytekwire.com/
(a bit harder to navigate their web site but lots of good electrical supplies)
 
Bud, I just did mine and while it took some time to get my brain around it, once you do that (and have a diagram taped to your wall), it isn't difficult. I made a supplemental wire harness with the relays on it that is almost invisible. I used 4 relays - 1) low beam 2) high beam 3) horns 4) driving light. The headlights come off a direct line from the solenoid and there is one wire running to the dash (driving light the switch is the "spare" forward/backward switch on the wiper stalk) everything else is basically ahead of the rad. The power for the horns and the driving light both come from the old horn wire. I can talk you through it if you want. I also strongly suggest you use the harness (tails) as well as the relays. Bosch is the most common relay brand but mine are no-name 40 amp.

BTW if you PM me, I also have the Classic Motorsports article scanned from teir Midget resto. It's somewhat helpful
 
Morris said:
Check it out:

https://cgi.ebay.com/ebaymotors/10-PACK-3...sspagenameZWDVW

or

https://cgi.ebay.com/5-PACK-12V-DC-30A-40...1742.m153.l1262
Click to expand...

Looks like a deal to me. It would be nice to know if they are a name brand; maybe the seller can tell you.

I bought a bunch of Panasonic automotive relays, 40A SPST without connectors for about $4 each from Digi-key electronics some time ago. See https://www.digikey.com, part no. 255-1828-ND. These have a tab that makes them easy to mount, and I just use 1/4" push-on terminals.

Whatever you do, don't pay $15 each or whatever they charge to get them from the usual LBC parts outlets. Total ripoff!
 
Anyone tried this from VB? For $30 you can hardly build your own. Headlight Harness
 
But for about the same money you can build one that is much better quality and have the exact wire lengths you desire.

I've seen that kit and the wire is cheap and the covering is pretty flimsy.
 
I have not seen the VB kit before. I think it is very well priced and complete. All it appears to lack are inline fuses. I may order one for my project Spitfire. Thanks for posting.
 
These seem like they will do the trick.

SPDT Relays with 5 wire sockets

I'm buying some now. I put in Halogens a couple weeks ago, so I had better protect my light switch!
 
I was looking at the old headlight harness. It's pretty chewed up, sockets at the headlights are also crappy, I may need it all which makes this kit compelling.
 
Here are my thoughts... You WILL end up modifying any "universal" harness that you buy. You will very likely not be happy with the quality of the components. You may not like the color of the wire wrap (the one I saw was bright yellow).

You will have a better looking installation if you buy the components and wire yourself (you can even retain Lucas color codes).

I have nothing against VB, but that universal harness is $30 for a reason.
 
You could be right. Might be more work but will likely be better, look better and "fit" better, and cost a little less.
 
I redid the harness for Bugsy so I could put a quick disconnect together for the front tilting BE Bonnet. I was able to buy properly color coded wiring from British Wiring, same people who build harnesses here in the states by the meter. I gave them the list of all of the wire colors I needed and they supplied new OEM type wiring and correctly color coded. It may not be you who needs to trace a wiring issue in the front end some time in the future but be nice to the future owner who needs to solve an issue you might have inadverently created. All of the connector, wires, and miscellaneous parts and pieces I needed to go from where the turn signals, horn, and headlight wires come out of the harness came to < $50.00. Do it right and do it with the proper materials. You'll thank yourself years in the future.

PS Get yourself a proper wire stripper, crimper, and soldering iron along with some heat shrink and tie wraps. BTW a trailer harness plug and socket makes a dandy waterproof quick disconnect for all of the wires needed up front.
 
I went to a wrecking yard and got 5 pin GM Delco relays- any GM car- look for early 90's and older Buick, Oldsmobile, Chevrolet, Pontiac, Cadillac or GMC- as the OEM Delco brand relays are getting hard to come by ( Since Delco/Delphi are not made in the USA anymore, aftermarket replacement ones are made by a foreign supplier and are not sealed and are succeptible to moisture). I can pick up a bunch of them and the relay sockets cheap (all with a set of wire cutters, the willingness to spend some time walking around the wrecking yard and all I can grab for 20-25 bucks.

On my 79 Midget I used the GM relays for the following:

1 Low beam headlights.
2. High beams
3. aftermarket Electric fan
4. Electric fuel pump.
5. Horn.

All the 5 pin GM relays OEM are 30 AMP min rated.
 
On my Morris I used a single relay for both high and low beam. It can be done if you stare at the diagram for awhile and think it over.

Glen
 
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