val fulesday wrote:

I am wanting to keep the relays inside the car , on the fire wall

So you want the relays in the cabin. The power has to come from somewhere, and its best to have the relays up front near the battery so the wire runs are short and can be large gauge wire. It doesn't make a lot of sense to run the power into the cabin to the relays and back out again to the lights.
Maybe its best to ask what you are doing, why you want relays, and what lights will you be using? 

Last edited by Mach1Driver (1/13/2022 5:29 AM)

Here is a good "how to"
No need to buy a kit,  relays are available almost antwhere.
https://www.youtube.com/watch?v=bcY2CG07wi0

Rudi wrote:

Here is a good "how to"
No need to buy a kit,  relays are available almost antwhere.
https://www.youtube.com/watch?v=bcY2CG07wi0

I watched that video and it makes the process much more difficult than required.  If a person uses a harness like the one I linked to, then they don't need to cut any existing wires on the car.  All the work can be done under the hood.  Just unplug both headlights and plug the new male headlight connector of the harness into one of the existing female headlight plugs (it doesn't matter which one).  This connection will complete the trigger portion of the relays.  Then connect the new Red wire, that is already fused, to the battery (or hot post of the solenoid).  Connect the Black wires to ground.  Use the two new ceramic female headlight plugs to connect to the headlight bulbs.  The circuit is now functional.  Of course, the installer would have chosen how to route the harness so that it is not seen.  During this process, a suitable location for mounting the relays would have also been selected.
 

Last edited by Rufus68 (1/13/2022 6:53 PM)

Beware of the relays with clear plastic housings that show the coil and contacts. I used a harness that came with that type, and they self-destructed after they got wet. Best to use only good sealed relays like Bosch or OEM.

Thanks for the diode explanation guys. It help. Since I used relay part numbers from Bullet Bob’s cheat sheet, my ride may have the diodes!!  
 

Nos681 wrote:

The diode protects the relay contacts as well as any electronic sensitive equipment connected.

Although this video pertains to 5 volt system, it still applies to 12 volt systems as well.

https://youtu.be/oMjNsoG6ZIA

 
Great video Dan.
 

Dkralc wrote:

This is a good explanation of headlight relays.

http://www.gtsparkplugs.com/headlight-relays.html
 

 
Sizing wire was something I struggled with on the Mustang as I adapted circuits in the painless harness. In the end, it was some reverse engineering using the type of wire they supplied with the corresponding fusing. All wire insulations are not created equal with some… different insulations will allow more or less ampacity through the same size wire. The link from =10ptDkralc has a section for wire capacity with a link to a wire size calculator that could be very helpful.
 
Val, what did you decide on. If you want the relays under the dash somewhere, it’s possible.  

ponch0v wrote:

Beware of the cheap Chinese headlight wire kits that are on Ebay. The wiring is under sized. Looks like 12g wire on the outside but cut and strip and see there is about 1/2 the copper that is in a 12g AWG wire.
 

Also, if you build your own be careful with Auto Zoo or O'Reilie's or most other auto parts store wire.  I use only GXL insulated primary wire from Allied Wire & Cable.  It's top quality and will withstand the high and low temps found under the hood...depending on the season.  Also, if you solder it the insulation will not crawl back up the wire an inch to get away from the heat.  It will cost you a bit more but....well you know.

BB1

Right you are about soldering, Rudi...don't ax how I know.  But in some instances soldering is necessary, just don't bend the harness at those points. 

Preach it Sally!

Before I got fed up with archaic original wiring  I chased an intermittent ignition cut out for almost a year.
I lost ignition once on a  very busy  Pennsylvania thruway  with no shoulder to pull off on, I thought it was gonna be the end of my wife’s and my life. It started up and quit many times on that trip but we did make it home in the end.
I couldn’t pinpoint the issue till one day I was trying to find the problem and got so pissed off that slammed the driver door so hard it almost came off the hinges. With that shock to the body the engine quit running and a light bulb came on in my brain, hmmm vibration = engine stopped!!.
The engine started right back up, which it usually did after quitting and got under the hood and started to jiggle the wiring harnesses exiting the fire wall. Lo and behold the wires that went to the CD ignition control box had a joint. The joint was a crimped wire joining connection that had been soldered and double covered with shrink tubing. I cut the bad section out and redid the connection with no solder, just crimped and shrink tubed. Issue solved.
That winters project was a complete AAW kit.
Lesson learned, the hard way . . . .  as usual!

My 2-cents.
I avoid using insulated butt splices or ring terminals due to wire breakage at the end of the splice or ring terminal.  Using an uninsulated version, I then use heat shrink to cover the splice/ring terminal and about 1/2” of the wire.  This will stabilize the connection enough not to allow vibration to break the wire at the connection point.  I’ve seen insulated slices and ring terminals fail both in my work experience, and working on cars.
I apply solder to the crimped joint, especially if outside the vehicle’s interior, to keep out any corrosive elements from corroding the connection. 

JamesW wrote:

I'd like to see what tools people have and recommend for connector crimping.  I've got a couple but nothing I would recommend.  Especially non-insulated connectors that you heat shrink over.

Aerospace used ratcheting type that were pretty high dollar.  Not looking to spend 4 figures....

I have a very old Thomas& Betts plier type crimping toll #WT-111-M.  It was handed down from my father. I'm not sure if they are available 'new' anymore, but I see used versions are available on eBay. 
While I've used the rachet type crimping tool at work, I also do not want to spend the extra money for one.