Do i need a relay?

[sweetpeet]

I'm thinking about setting up an aux fuse box. Do i really need to get a relay too or can I just connect it to the main box with wires?

 

[PoliceMonkey161]

What do you plan to run off of the aux fuse box?

 

[sweetpeet]

What do you plan to run off of the aux fuse box?

Everything that's not on the main. Lights, radio, cb,

 

[PoliceMonkey161]

I would not "jump it" from the current fuse block. Consider runing new wires from the battery including a main fuse in-line. Not sure why you would need a rely prior to a new fuse block unless the new block where only powering circuits that required a "key on" circuit? I that case, yes you would need a main relay or independent relays for each device.

 

[sweetpeet]

I would not "jump it" from the current fuse block. Consider runing new wires from the battery including a main fuse in-line. Not sure why you would need a rely prior to a new fuse block unless the new block where only powering circuits that required a "key on" circuit? I that case, yes you would need a main relay or independent relays for each device.

Yah, I'd need a key on and I could prob jump that too but it's probably better to not redneck it.

 

[PoliceMonkey161]

It's not as hard as you think......... You'll still run the new wires from the battery as described, you'll just be adding a mini relay to the postive line. The coil to the relay (A and B) can be enregized by any circuit works during the "key on" position. If you only need a "key on" and not a "acc. on" fuse block, you could use the igintion wire. Regardless, you have several options as the control wire for the new relay.....ie: feed wires to wipers, radio etc.

 

[greg92jeepxj]

Question ? For every relay added , should each be preceded by a fuse ? I would have to closely read a wiring diagram , but I think the terminal 85 and 86 circuit have fuses , don't remember the 30 & 87 circuit having a fuse , am I right ? Well , in this case , should a secondary power supply being added be wired with a fuse before each relay , 85 & 86 as well as 30 & 87 be added ?
Recently , I added a relay to a car for an electric fan added on . May want to gang a second relay like some factory installations . But I never pre-fused the switched circuit or the power circuit ! Shame , I know . And I know better ! I think I got a job this weekend before the hot weather gets here and the fan really starts kicking in ! Guess I will have to run fuses to each circuit , 85 ,86 & 30,87 ? Don't want this to go wrong , I don't do things like that ! Glad I saw this post , any advice regarding much appreciated ! Thanks in advance , Greg92jeepxj.

 

[greg92jeepxj]

Just checked my service manual , couldn't rest knowing a potential mistake could've been made . Yes, switched circuits 85,86 are fused ( from what I read ) and 30,87 are fused with the larger fuses . Now realizing the need for mini and MAXI fuses . Red face .

 

[greg92jeepxj]

It's not as hard as you think......... You'll still run the new wires from the battery as described, you'll just be adding a mini relay to the postive line. The coil to the relay (A and B) can be enregized by any circuit works during the "key on" position. If you only need a "key on" and not a "acc. on" fuse block, you could use the igintion wire. Regardless, you have several options as the control wire for the new relay.....ie: feed wires to wipers, radio etc.

More thoughts on this ; the car , an '85 olds cutlass 3.8 ltr. RWD needed a pusher fan in front of the condenser to help cool better . Not having a factory electric fan , I added it . Now will just tee in fuses to the 85,86 circuit & 30,87 circuit .

 

[Turbogus]

Hey Peet, ltns! I'm finally getting to that PDB i pulled from a mid '90's Ford truck;



...and made a small discovery, all of the relays on the backside of this PDB have their signal wire connected to a corresponding fuse. Saves me some time fusing each circuit and keeps it all nice and compact in a single box that fits on my inner fender near the battery. This PDB has a 4 gauge (I think) primary connector that I'm linking directly to the battery. Will post photos when it gets done.

 

[PoliceMonkey161]

More thoughts on this ; the car , an '85 olds cutlass 3.8 ltr. RWD needed a pusher fan in front of the condenser to help cool better . Not having a factory electric fan , I added it . Now will just tee in fuses to the 85,86 circuit & 30,87 circuit .

Not sure what you're asking? Are talking about a 85 Olds or a XJ? Not certain what circuits 85,86,30 and 87 are? Are you running two fans on one engine/vehicle?

 

[PoliceMonkey161]

Question ? For every relay added , should each be preceded by a fuse ? I would have to closely read a wiring diagram , but I think the terminal 85 and 86 circuit have fuses , don't remember the 30 & 87 circuit having a fuse , am I right ? Well , in this case , should a secondary power supply being added be wired with a fuse before each relay , 85 & 86 as well as 30 & 87 be added ?
Recently , I added a relay to a car for an electric fan added on . May want to gang a second relay like some factory installations . But I never pre-fused the switched circuit or the power circuit ! Shame , I know . And I know better ! I think I got a job this weekend before the hot weather gets here and the fan really starts kicking in ! Guess I will have to run fuses to each circuit , 85 ,86 & 30,87 ? Don't want this to go wrong , I don't do things like that ! Glad I saw this post , any advice regarding much appreciated ! Thanks in advance , Greg92jeepxj.

Regardless on the application, each relay needs its own fuse on the supply/positive line. Ideally, the fuse would be 25% larger than the total draw or highest single use device.

 

[greg92jeepxj]

Not sure what you're asking? Are talking about a 85 Olds or a XJ? Not certain what circuits 85,86,30 and 87 are? Are you running two fans on one engine/vehicle?

Hey thanks for the reply . Real sorry to cause confusion . I was just using the '85 olds as a reference to a job i did but my real question is in general , when you add a relay , should you install fuses to the power supplies for terminal 30 and for terminal 85 ? I did not and feel that since all that is in line to the added pusher fan is wiring and a relay . Power from ignition terminal to 30 and power from temperature sensor to 85 to make the fan run . Done right or need fuses ?

 

[greg92jeepxj]

Regardless on the application, each relay needs its own fuse on the supply/positive line. Ideally, the fuse would be 25% larger than the total draw or highest single use device.

Hey , you answered my question before I could write my post . LOL ! I better learn to tape faster ! Terminals 30 and 87 connect to component you want to power but cannot without the help of terminal 85 and 86 . 85 and 86 create a magnetic field in the relay to close a switch for 30 and 87 to carry the current to the component . Sorry for the confusion and greatly appreciate your reply ! Thanks again , Greg 92jeepxj

 

[PoliceMonkey161]

Gotta ya! 85 and 86 would be the coil (often A and B in a generic schematic). If the coil of the relay (85 and 86) are energized by the ignition, you would not need an addition relay, the stock circuit would already have one and the AMP draw of the relay coil is minimal.

Anytime Brother!

 

[greg92jeepxj]

Thanks again ! That makes me feel a lot better ! That's why I ask someone with more experience with volts than me . I can rig up a system but am lacking some in electrical theory . I needed to know exactly that , what the line carries and as you said the ignition will regulate that . Thank you sir , I just know you guys will keep me out of trouble and not burn down the house when left home alone ! I really appreciate an experienced how to guy making sure I learn right . Thanks big brother ! Greg92jeepxj