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Adding a relay fuse box?


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#1 Aman

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Posted 12 September 2017 - 05:59 PM

Right now I have a 6-circuit fuse block getting its power from the 16AWG or possibly larger black/white wire from the fuse box. It doesn't have a relay, but I've only run a radar detector off of it, so I guess I've never really pulled too much power from it. I ran through the electrical manual and it looks like this wire is ignition on, and powers the coil and the main relay, as well as many other bits from the fuse box. I'd like to add a relay since I'm going to be powering injectors and coils off of it with MS3, but I'm not exactly sure how to go about that. I do know how a relay works though. Here's what I'm thinking.
1. Run the wire from black/white to pin 85 of the relay
2. Run the wire from pin 86 to chassis ground
3. Run pin 87 directly from battery
4. Run pin 30 to the fuse block.

So here's what I'm missing. The injectors use a 10 amp fuse, the coils run a 25 amp fuse. Do I need to, in some way, fuse the black/white signal wire? Also, my mind says run a 40 amp fuse for the block power, giving me some room to also run gauges. Is 40 amps big enough?

Send help, I'm scared of setting things on fire
1987 Chrysler Conquest - Originally Shetland beige - JDL EL divided T3 - Genuine HX35 8-blade - CXracing intercooler and piping - Trunk mount Optima Yellow -
TiAL 38MM MVS x 2 - Maxboost MPI running MS3 - CNP ignition - Stock head (Yeah, yeah, I know.) - Stock bottom end with 50K original miles at stock
levels, sat in garage for 30 years
2000 Ford Expedition- Oxford White - Waiting on the Quest to be done to get a BTS transmission - Daily driver





#2 Turbo Cary

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Posted 12 September 2017 - 06:50 PM

You should run a relay for each seperare circuit that receives power from that fuse block IF the circuit requires it.

For example fuel pumps have a relay so they are switched on when the ignition is turned on.

Usually pin 87 and 30 are the switched ones. 87 being the load side of the relay. (Ex fuel pump) the 85 is fused battery voltage (the size fuse you need for the circuit amp) and then 86 ground. The 30 pin would be the switch side.

#3 Aman

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Posted 14 September 2017 - 01:44 PM

But would I be safe running the black/white to one side of the relay and the other side to ground? I won't burn anything will I?
1987 Chrysler Conquest - Originally Shetland beige - JDL EL divided T3 - Genuine HX35 8-blade - CXracing intercooler and piping - Trunk mount Optima Yellow -
TiAL 38MM MVS x 2 - Maxboost MPI running MS3 - CNP ignition - Stock head (Yeah, yeah, I know.) - Stock bottom end with 50K original miles at stock
levels, sat in garage for 30 years
2000 Ford Expedition- Oxford White - Waiting on the Quest to be done to get a BTS transmission - Daily driver

#4 Turbo Cary

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Posted 14 September 2017 - 08:47 PM

View PostAman, on 14 September 2017 - 01:44 PM, said:

But would I be safe running the black/white to one side of the relay and the other side to ground? I won't burn anything will I?

I think this may be a question for the Multiport/Tuning section. Without seeing a wiring diagram it is hard to say. You should list where each color wire is coming from to help determine how it needs to be wired.




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