RB26powered74zcar Posted January 28, 2007 Share Posted January 28, 2007 Hey guys, I'm looking for some simple help here. I'm installing a complete new 12 circuit harness in my Z tomorrow, from headlights to taillights.... What I need right now is to simply be shown how to wire up a auto relay. I bought 10 new 40a Bosch 5 blade relays, but don't know the basics to hooking one up. So if I were to for example want to wire a electric fuel pump to one, what wires go to which blades on the relay? I'd have to go outside a dig them out of the car, but for example, each terminal on the relay has a number on the spade connector. Can you tell me how to wire one up using the blade numbers please? BTW, I searched here but didn't see anything relavent> http://forums.hybridz.org/search.php?searchid=758588 Quote Link to comment Share on other sites More sharing options...
vashonz Posted January 28, 2007 Share Posted January 28, 2007 the only thing the 5 blade relays have is an 87a that is optional to use. what it does is when the 86-85 circuit is completed the relay switches from 87a to 87. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted January 28, 2007 Author Share Posted January 28, 2007 Ok vashonz, thank you very much for the diagram, its very helpfull. I'm still confused though. If I were hooking up a fuel pump to the relay shown above, where would the + wire of the fuel pump hook to, and where would the - wire from pump hook to? Quote Link to comment Share on other sites More sharing options...
jimzdat Posted January 28, 2007 Share Posted January 28, 2007 In the upper right of his diagram, where it says "fuel pump" and all that?--the wire that comes off of terminal 87 would be the positive wire to the fuel pump. The ground for the fuel pump would simply be attached to the body, or run up to a central ground point if you choose to use one For standard relays-- Terminal 87 is "normally open"; the circuit closes when power is applied to the relay coil Terminal 87A is "normally closed"; the circuit opens when power is applied to the relay coil--this is used for ignition cut-outs and that sort of thing Be careful of buying relays at Autozone and the like that are in their foglight section--some of them have two 87 terminals, but they appear to be a 87 and 87A Quote Link to comment Share on other sites More sharing options...
jimzdat Posted January 28, 2007 Share Posted January 28, 2007 Here's a link that might help explain the relay a little better too: http://www.fordfuelinjection.com/index.php?p=42 Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted January 28, 2007 Author Share Posted January 28, 2007 Thanks for the great pic refernces guys!! I still don't get the part in that pic that shows 85 going to ground and 87 going to ground. So, would # 30 hook to the battery constant hot. And # 86 hook to a 12v switched power source And # 87 hook to the 12v + lead on the fuel pump So what would # 85 hook to from the relay, and 87a ? Quote Link to comment Share on other sites More sharing options...
Warren Posted January 28, 2007 Share Posted January 28, 2007 85 is a ground for the relay itself, connect a wire from 85 to ground (the body) Terminal 87A is "normally closed"; the circuit opens when power is applied to the relay coil--this is used for ignition cut-outs and that sort of thing... 87A can be left open, with no connection...it's NOT necessary to use it. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted January 28, 2007 Author Share Posted January 28, 2007 Awesome!! I think it finally sunk into my thick scull...lol Thanks for the replys - joel Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted January 28, 2007 Share Posted January 28, 2007 I hope that I do not cause additional confusion with this but... the primary function of a relay is to allow you to to use a low load source to complete a high load circuit. A good and common example of that is using a relay for your headlights, if you look at the drawing that vashonz shows you can see how to connect a wire from your battery to your headlights, when the relay is off (no power from the switch to blade 86) you have an open circuit in the relay and no electricity can flow, when the switch is turned on power will flow through the coil between blade 86 and blade 85 causing the contacts between blade 30 and blade 87 to close and your headlights to come on with current directly from the battery. What you have done in this excercise is used a very low current load through blades 85 and 86 to connect a path for a high current load between blades 30 and 87. This allows you to use less heavy gage wire and switches in your car and reduces the likely hood of melting wires by overloading them when you put in a 30 amp fuse instead of a 10 amp fuse (not saying you are going to do that but I see it all the time and everyone knows someone who has done that). Dragonfly Quote Link to comment Share on other sites More sharing options...
Careless Posted January 31, 2007 Share Posted January 31, 2007 I hope that I do not cause additional confusion with this but... the primary function of a relay is to allow you to to use a low load source to complete a high load circuit. A good and common example of that is using a relay for your headlights, if you look at the drawing that vashonz shows you can see how to connect a wire from your battery to your headlights, when the relay is off (no power from the switch to blade 86) you have an open circuit in the relay and no electricity can flow, when the switch is turned on power will flow through the coil between blade 86 and blade 85 causing the contacts between blade 30 and blade 87 to close and your headlights to come on with current directly from the battery. What you have done in this excercise is used a very low current load through blades 85 and 86 to connect a path for a high current load between blades 30 and 87. This allows you to use less heavy gage wire and switches in your car and reduces the likely hood of melting wires by overloading them when you put in a 30 amp fuse instead of a 10 amp fuse (not saying you are going to do that but I see it all the time and everyone knows someone who has done that). Dragonfly i just think of it as a switch board in another room. when i turn this light on, you go do this for me. Quote Link to comment Share on other sites More sharing options...
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