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 Post subject: relays or no relays
 Post Posted: Fri Jan 19, 2007 9:54 am 
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heres what I got, street legal race car. will run battery in right rear, safety switch in right rear taillight lens, welding wire 0 gauge up to shifter area were there will be high amp painless kill switch, from there to pasenger side firewall ford type solioid. From soliod to starter and from soliod to painless fuze panel pro street type. all race circuites pluss some street legal stuff. I will have fuel pump,waterpump,fans,line loc,ign,starter,lights headlights and brake lights and turn and maybee horn that will be it. Should I use relays or not? My wire will come from fuse panel that has fuses and will go into jegs panel with off on toggle switches. the fuse panel has a in wire for power that is 10 gauge ken it was already installed. It will see very little street use, and safety clean and simple is what I want So what do you all think?

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 Post Posted: Fri Jan 19, 2007 10:00 am 
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This is my reply I sent him via PM when he requested info.

Mark I don't normally use relays because they are just another thing to have to look at when problems occur. Example, if the water pump stops working, is it the relay or the switch or the pump fuse? See where I'm going? However, I'll admit there is possibly a reason a relay might be in order. Extremely high current draw (30+ amps) would be the only reason, IMHO.

Most all parts of your electrical system will do fine with 14ga wire. Tail lights, turn signals will be fine with 16ga. Headlights need 14 at a minimum.

The wire gauge you run from the power soruce to your fuse panel should be larger. That needs to be large enough to handle power requirements of "several" items running at once, ie, water pump, fan, igintion circuit, CD player, etc. and would require 8 or 10 ga at a minimum. If you're going to add A/C and heat in the mix then 8ga probably would work best.

Remember, if you're going to have this car at an NHRA race track and have to pass tech then a master disconnect must be installed in the rear and it has to kill the engine to pass tech.

And to be on the safe side, I'd pm someone else and get some input from another source. You can NEVER have too much information when you're working on a project like this. If you want to start a thread on this I'll move this message over there so others can give their opinion.

Later bud!!

Post edited to remove stupid statements! =;

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Last edited by Ken0069 on Fri Jan 19, 2007 11:59 am, edited 1 time in total.

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 Post Posted: Fri Jan 19, 2007 10:06 am 
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so ken I beieve you are telling me to power up that fuse panel from the battery side of that kill switch at the shifter instead of the soliod ford type, even though all power to soliod will come through the kill switch, does it matter?

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 Post Posted: Fri Jan 19, 2007 11:55 am 
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spib wrote:
so ken I beieve you are telling me to power up that fuse panel from the battery side of that kill switch at the shifter instead of the soliod ford type, even though all power to soliod will come through the kill switch, does it matter?


Hummm, I think I had a brain fart. Yes, you can pull power for your panel from the solenoid as it will be shut off when the disconnect is switched off.

Sorry, it's the charging wire on your alternator is what I was thinking about. If that wire is connected to anything between the solenoid and your disconnect switch then the engine will still run on alternator output even though the battery is disconnected. It is a good idea to run a one wire alternator for this also as if you run a 3 wire, one of those has to have a diode in it go keep the engine from running on. I ran into that problem with my Studebaker.

Yeah, that's what I ment. My original post was made from bed this morning! O:) I guess I wasn't awake enough to be thinking clearly. =; It's hell to be retired! What day is it anyway? =;

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 Post Posted: Fri Jan 19, 2007 1:04 pm 
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will buy 1 wire alt and run all the way back to battery box.

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 Post Posted: Fri Jan 19, 2007 1:14 pm 
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Ken0069 wrote:
spib wrote:
so ken I beieve you are telling me to power up that fuse panel from the battery side of that kill switch at the shifter instead of the soliod ford type, even though all power to soliod will come through the kill switch, does it matter?


Hummm, I think I had a brain fart. Yes, you can pull power for your panel from the solenoid as it will be shut off when the disconnect is switched off.

Sorry, it's the charging wire on your alternator is what I was thinking about. If that wire is connected to anything between the solenoid and your disconnect switch then the engine will still run on alternator output even though the battery is disconnected. It is a good idea to run a one wire alternator for this also as if you run a 3 wire, one of those has to have a diode in it go keep the engine from running on. I ran into that problem with my Studebaker.

Yeah, that's what I ment. My original post was made from bed this morning! O:) I guess I wasn't awake enough to be thinking clearly. =; It's hell to be retired! What day is it anyway? =;



You can look at my other post but I'll save you the time...To day is Friday =;

I like relalys as It takes all the load off the switch... So you don't need a 14 size wire from the switch....I would use a relay for the fuel pump and put it as close to the pump as possible and make sure you fuse the power wire to the relay..... =;

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 Post Posted: Fri Jan 19, 2007 2:01 pm 
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If you use a good quality switch and don't exceed it's current rating relays aren't necessary. The one exception I would make is the fuel pump. There is going to be some drop in the length of wire you run back to the pump even if your switch is rated high enough. the battery is right there near the pump and with a relay there you get almost no drop.

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 Post Posted: Fri Jan 19, 2007 3:27 pm 
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Yep. Basically what Chuck and Barry said. If you use relays you can use lighter gauge wire which is easier to work with and lighter. But you really need to have the fuel pump on a relay for the reason Chuck gave. I use 2 relays...one on the fuel pump and one for my alternator. The one for the fuel pump is a 30 amp and the one for the alternator is a continuous duty 85 amp. On the old car I had a knife switch on the positive battery post for the alternator but then if we forgot whether the switch was on or not we had to pull the deck lid to check it out. Now I have a switch mounted on a subpanel with a little green light on it that tells me when the alternator is on. I like to kill it so there are no hot wires for a dropped wrench to find around the front of the motor. Do not use a Ford type solenoid for this as they are not rated for continuous duty. They are rated for a high amperage draw for a short duration. A continuous duty relay is just that. It's rated to handle the rated amperage indefinately or until it burns up...which ever occurs first. =;

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 Post Posted: Fri Jan 19, 2007 4:12 pm 
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=; I got a belt drive fuel pump! O:) =; \:D/

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 Post Posted: Fri Jan 19, 2007 4:46 pm 
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Ken0069 wrote:
=; I got a belt drive fuel pump! O:) =; \:D/




power sucking belt pump O:)

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 Post Posted: Fri Jan 19, 2007 6:23 pm 
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My fuel pump has two relays, per manufactures instructions. I like relays, but you must buy good ones.

I think Ken is lost in the 60s with that big wire, big switch theroy, It will work though and work well, just need to be careful selecting switches.
Greg =;

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 Post Posted: Fri Jan 19, 2007 6:42 pm 
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Hell I know a few guys around here that wired up cars with NO FUSES!! O:) Tweren't me though. I do use fuses.

And while we're talking about fuses, do you fuse the circuit that activates the relay? If not, then why not? It's a seprate circuit isn't it and could short out somewhere along the run in the harness and catch fire.

Do you also fuse the feed to the relay? If not why not? It is a seprate circuit just like the one that activates it and could catch fire if over loaded or is shorted out!

So if you run relays, IMHO you still need to fuse the circuit that activates that relay as well as the relay circuit itself. So if that device doesn't work, then there are actually two circuits you have to trouble shoot and two fuses to check.

Not saying that either way is right or wrong. Just that the less complicated you can make something, the better off you are in the long run, especially on race day, like between rounds and something isn't working. It might make the difference in making the next round, or loading up and going home cuz you missed the call working on the car.

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Last edited by Ken0069 on Fri Jan 19, 2007 6:45 pm, edited 1 time in total.

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 Post Posted: Fri Jan 19, 2007 6:45 pm 
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no fuses for us, will put the wires out rather than loose the race!! [-( let "em smoke their is new ones where the old ones came from.. we are surrounded by water though so it will not go too far. #-o =;

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 Post Posted: Fri Jan 19, 2007 6:50 pm 
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tonyy358 wrote:
no fuses for us, will put the wires out rather than loose the race!! [-( let "em smoke their is new ones where the old ones came from.. we are surrounded by water though so it will not go too far. #-o =;


Yeah well I'd bail out of a burning boat at speed, after all, there is plenty of water around you!! =;

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 Post Posted: Fri Jan 19, 2007 6:55 pm 
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I fuse the wire that feeds the the switch side of the circuit. Then I have a buss bolt in fuse..80 amp that feeds everything on the car. It worked flawless for 3 seasons until the last race last year. During the burnout it blew the big fuse, I have not found any problems and have pulled everything out of the car an checked it. I think it may have been due to vibration? It will not have one next year at all.

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