Relays

Relays

The wiring on old cars like the Maverick have a design where full power is moved thru the switches in the cabin. Fore example, when you blow the horn or turn on the headlights, all the power goes from the battery thru the switch in the car then back out to the horn or lights. This puts full power on the switch. Which can be a safety and fire hazard. So to that end I put in some relays to reduce the power going to the switches. 

 


Here is the relay I used. Its called a Bosh 87a style relay. It has one Normally Open and one Normally Closed set of contacts and one coil.  The battery positive is connected to pin 30 and  the load (i.e. horn) to power is connected to pin 87. This supplies the high current to power the load. The switch for the load, horn button or headlight switch. is then connected to pin 85 and pin 86 is grounded (this can actually be reversed too with the switch on 86 and 85 grounded). This puts a LOW amp draw from the headlight/horn switch that engages the coil, thus putting the high amp load thru pins 30/87 to power the load.

 


Here you can see the relay wired up. Notice how the high current stays going thru the relay only, which is activated by low current going thru the switch. This makes it much safer by not putting high current draw thru the switch in the car cabin.

 


I got a set of relay and holders. The small relays are the Bosh 87 knock-offs, and the bigger relay with white writing is a 10sec delay relay. 

 


I then made a wire harness to go across the car since I mounted the relays on the passenger side and the existing wire harness for lights and horn were on the drives side. Why didnt I just mount the relays on the drivers side? Because you want to keep your relays close to the power supply, which in this case is the battery.

 


I then wired it all together using blue butt splices. I am not really a fan, so I hope they hold. The color tape is just until I get the load side wired up. The big black bar is a common ground, and the big red bar is a power bus. The littel red thing on the left is a 30AMP circuit breaker that is inline to my fan.

Once I have the load side done, turning on the headlights will trigger the low current side of the relay which will then allow high current power to flow to the headlights.

The relays are for left to right.. 1)Fan 2)Horn 3) low beam lights 4) High beam lights.

 

Click here for more pictures