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Discussion Starter · #41 ·
That's my question, if I have switches that are rated for 30 amps each and properly fused do I need relay's, I've read many opinions doing it both ways. The two pusher fans are 10 amps each and the puller fan is 12 amps so I'm wondering if a 10awg wire is ok or if I should be running 2- 12awg wires to the switches or relays?
 

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OK. Tough love time.

Adding an extra wire from the battery to the alternator does nothing to solve the problem with the ignition switch.
REMOVE ALL THE HIGH AMPERAGE ACCESSORIES FROM THE FUSE BOX!!!

The fuse box gets its power from a single 12 gauge wire which is barely sufficient for a stock car. This is why Pontiac added second 12 gauge wire to run pwr seats and windows, and a third to operate the A/C.

Operating high amperage accessories without a relay will in turn burn the contacts on your toggle switches unless they are rated for 20 amps or more.

Relays are one of the simplest wiring jobs to do. Read the material others and I have suggested and educate yourself before that beautiful car of your is no more than burn't sheetmetal
 

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Since your car is far from original, just add an auxillary fuse block. Easy enough to do. Supply the fuse block with a 12 Volt source independent of the car's wiring harness, add you connections/switches/fuses and you are done. Added a fuse box and auxillary box to my brother's 1948 International seeing they did not have fuse boxes and I rewired the entire truck adding fuses to protect all the wiring like a "modern" car.

Pic #1 is the power wire that is tied into the battery/starter lug and goes into the truck to power the fuse box.

Pic #2 is the fuse box. You can see the red power wire at the base of the box. I used the modern spade type fuses and when they burn out, they have an LED light that will glow telling you which fuse popped. Above that is a power strip/junction. The fused wiring from the fuse box then goes to my power strip/junction. Then on the same lug/connection of the power strip/junction, the wire goes to the light (s) and powers those lights. Makes it easier for me to connect the wires using soldered ends, as well as fast individual testing should I have a light (s)/wiring failure or issue, and makes it easier to replace an individual wire should the need arise.

Pic #3 is a manual 12V shut-off switch I installed between the battery cable coming off the battery, to the switch, then to the starter lug on the starter solenoid. A 12V shut off switch should be wired into any of out older vehicles to protect them from wire fires - which can happen even if you are nowhere near. I have too much time/money invested in my vehicles to have a short catch it on fire and burn it to the ground whether I am in the car or not. And if you put your ride in a garage, is it worth taking a chance in having your house burn up with the car?

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Discussion Starter · #44 ·
OK. Tough love time.

Adding an extra wire from the battery to the alternator does nothing to solve the problem with the ignition switch.
REMOVE ALL THE HIGH AMPERAGE ACCESSORIES FROM THE FUSE BOX!!!

The fuse box gets its power from a single 12 gauge wire which is barely sufficient for a stock car. This is why Pontiac added second 12 gauge wire to run pwr seats and windows, and a third to operate the A/C.

Operating high amperage accessories without a relay will in turn burn the contacts on your toggle switches unless they are rated for 20 amps or more.

Relays are one of the simplest wiring jobs to do. Read the material others and I have suggested and educate yourself before that beautiful car of your is no more than burn't sheetmetal
Ok I get that but the wire to the alternator was suggested here and can't hurt now that it's in place and now that I've found my boneheadded mistake I will be correcting it and my switches are Doorman oval ones with the indicator light that are rated at 30 amps, I've heard of relays burning out too since they only cost 3.99. I'm going to run two 12awg wires instead of one 10awg. I'll check what I have plugged into the fuse panel but I'm pretty sure it's low amp stuff like a glove box light, the stereo head unit not the amps, those have a 2awg right to the battery. Thanks for the help.
 

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One reason to use relays is to eliminate the need to run heavy gauge wires from the source to a switch and then to the load. If you use a relay the heavy gauge wire is not needed to the switch.
A low current is used to pull the relay which completes the circuit to the high current device which is wired with the heavy gauge wire.
So follow the advice add an external junction box and wire the relays and fans from this.

So instead of running two 12 gauge wires from the fans to the switches in the car just use relays.
 

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Discussion Starter · #46 ·
Got it, well I already ran the heavy wires from the fans when I installed them so now I was going run more wires from the battery for a power source instead of trying to tap power out of the fuse box which isn't right, does that make sense?
 

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Got it, well I already ran the heavy wires from the fans when I installed them so now I was going run more wires from the battery for a power source instead of trying to tap power out of the fuse box which isn't right, does that make sense?
The point is if you used relays you would not need to run any more heavy wires to the switches or the fans.
If you have the correct wires to run the fans what you would do is connect each fan to a relay the switches you have can then be connected to the switch side of the relay.
You will need to run a heavy gauge wire to each relay as the source. So you more than likely have enough wire to complete this since you do not need to run this all the way to the switches.

Instead of lights imagine your fans

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I use Bosch (made in Germany) relays in all my electrical work. They come in different amperages according to load. Never had one fail.

I think you're on the right track B65. It's your personal preference to use the 30 Amp switch or relays.
As mentioned, with relays, you'll reduce your big wire runs and voltage drops. With relays you can run a single 14 gauge wire from the battery terminal on the fusebox, daisy chain to each switch, and then a 14 gauge to each underhood relay from each switch. You want to keep the high amperage wire runs as short as possible. Install the relays after the circuit fuse as shown above. Jims pictures of a fuse panel would work well.
Mount the relays to the outer fender lip just behind the battery. Short wire run. You can mount the fuse panel on the inner fender near the battery and under the outer fender to reduce clutter.

The extra wire from the alternator to the battery is a good thing too but wasn't totally related to the ignition switch overheating. In doing all this, your solving several different problems.
Good winter project! Send pictures of your installation progress and we'll make sure your not fubaring it.
 

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Discussion Starter · #49 ·
Ok I understand, I'll have to see where I can mount the relays out of site and then have to tear apart my wiring to the fans that I hid neatly to do this, that's why I thought it might be easier to run a couple of wires from the battery to the dash switches and if I decide to use relays I would stick them under the dash but your right it's better to keep the power runs short as possible. If I was starting from scratch I would have done it differently....now that I get the concept I'll figure it out, thanks(y)
 

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Discussion Starter · #50 ·
So I'm going to do it right and use the two 30 amp relays and mount them behind the battery for a short battery power run then I can use my two wires that run to the switches as relay triggers. Only thing I have to get straight is getting power to the switches for the indicator lights, looking at diagrams I can pull power out of the fuse block for that to the 12v side of the switches then the acc terminal on the switches is my relay triggers, and keep my switches grounded to chassis like they are now, I'll hack into the fan wiring to install the relays using a chassis ground out there and a short peice of 10awg to power the relays, hopefully that's a big enough wire because I have about 32 amps with all three fans....does that sound right?
 

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Sometimes a drawing is easier to describe.

Switch wiring. 12 volts from the fusebox, Battery terminal if you want to operate fans with the key off or Acc with key in the Acc or Run position. OK to use fusebox terminal since the relay load is very small
Connect 12 volts from one switch terminal to the other.

Light is powered from the load (relay) side, other side to ground.

Add additional switches the same way


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Discussion Starter · #52 ·
Maybe my light bulb hasn't gone on yet but is the diagram missing a terminal, shouldn't there be 4 terminals? Where you show relay 1 relay 2 is that going to the fans or is that my short power lead from the battery?
 

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Discussion Starter · #55 ·
Ok so I'm rewiring my fans and have a couple questions for you experts, the power from the battery to the #30 terminal on the relays should that be a separate wire to each relay or can I go to one relay then jump to the other relay? The two pusher fans are 9 amps each and the puller fan is 12 amps. I'm thinking that's to much amperage for one #12 wire since those are rated for only 20 amps. Second question is the relay for the two pusher fans has two #87 terminals so do they both close the same so I could put a fan on each one?
 

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I would use 2 12 gauge wires from the bat / fuse one to each relay pin 30, now each relay can provide 20 amps with 12 gauge wire. If you wanted to you could use 14 gauge for the single fan relay.
For the relay to control the two fans use a switched 12 volts to pin 86 this can be a small gauge wire 16 or 18
Pin 85 is ground for the relay coil this can be the same smaller gauge wire as the switched input.
Run a 12 gauge wire from Pin 87 to the first fan + terminal and another 12 gauge wire from this fan to the second fan + terminal. For the ground connections on the fan use 12 or 14 gauge.

For the single fan do the same as above but you can use a step down in gauge for pins 30 and 87 if you want as it is drawing 12 amps 14 gauge is rated for 15 amps

I hope this helps
 

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Discussion Starter · #57 ·
I would use 2 12 gauge wires from the bat / fuse one to each relay pin 30, now each relay can provide 20 amps with 12 gauge wire. If you wanted to you could use 14 gauge for the single fan relay.
For the relay to control the two fans use a switched 12 volts to pin 86 this can be a small gauge wire 16 or 18
Pin 85 is ground for the relay coil this can be the same smaller gauge wire as the switched input.
Run a 12 gauge wire from Pin 87 to the first fan + terminal and another 12 gauge wire from this fan to the second fan + terminal. For the ground connections on the fan use 12 or 14 gauge.

For the single fan do the same as above but you can use a step down in gauge for pins 30 and 87 if you want as it is drawing 12 amps 14 gauge is rated for 15 amps

I hope this helps
I would use 2 12 gauge wires from the bat / fuse one to each relay pin 30, now each relay can provide 20 amps with 12 gauge wire. If you wanted to you could use 14 gauge for the single fan relay.
For the relay to control the two fans use a switched 12 volts to pin 86 this can be a small gauge wire 16 or 18
Pin 85 is ground for the relay coil this can be the same smaller gauge wire as the switched input.
Run a 12 gauge wire from Pin 87 to the first fan + terminal and another 12 gauge wire from this fan to the second fan + terminal. For the ground connections on the fan use 12 or 14 gauge.

For the single fan do the same as above but you can use a step down in gauge for pins 30 and 87 if you want as it is drawing 12 amps 14 gauge is rated for 15 amps

I hope this helps
Yes it does thanks, and I knew after I asked about the battery leads to the 30 terminal just was wanted a second opinion. I'm not sure if I got it straight on the two fan relay, it's a 5 pin with two # 87 terminals so I have it wired with each positive from each fan to the two #87 terminals will that work?
 

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Discussion Starter · #58 ·
After researching it some looks like I need a double output relay with an 87 and 87b so I don't end up with three relays....I'm understanding this now, thanks.
 

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Discussion Starter · #59 ·
I have a double output relay from Grainger ordered be here Monday and I separated the battery leads and installed the appropriate fuses, getting there 👍
 

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Discussion Starter · #60 ·
So here's an update on the rewiring of my fans the correct way, waited a week for the double output relay, had to hook the switches to battery because it was the last two terminals left on the fuse block. Also installed a new 140 amp alternator with an #8 wire directly to the battery and new belt, I went with black to match the steering pump but I'm not a 100% sure it looks better than the polished one, oh well. Ran it for about 20 minutes with the fans on and nothing got warm and no fuses blown so hopefully it's all good but we'll see next summer, thanks everyone for the great help in avoiding a disaster, some before and after pix
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👍
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