t_g_farrell

iTrader: (1)

Good point Pele. Thats exactly how I do all my vehicles. I guess that explains why
the last ignition switch I installed is still working.

So far I have relayed the headlights, electric fans and the fuel pump. Relays
are good things Especially for 30 year old vehicles.

85TIIDEVIL

iTrader: (2)

If the connection is good there shouldn't be any spark or arc, in other words the current doesn't have to work as hard to jump the gap. He says uptop there was a loose connection at his ignition wiring. Current being amperage, will go higher because the gap / loose connection / minimal contact area (whatever u want to call it) creates resistance, & when resistance goes up current goes up. If it's not enough to pop a fuse it will heat up your now undersized wire at the resistance point. Of course leaving things on when you switch the car on and off will add more circutry to be at chance for fault.

Just thinking out loud. I am an electrican, and electrical theory applies the same from whether it be commercial building wiring or electronics.

DivinDriver

iTrader: (15)

The act of closing (or oprning) a switch is what makes (or breaks) the connection - - when you turn something on, you are going from "no connection" to "connection."

If you do that under load with a DC circuit, you get an arc.

How much of an arc depends upon the size of the load, the voltage, and the nature of the contacting surfaces; material, cleanliness, speed & bounce (or lack thereof) of their mating. A good clean fast-closing switch making/breaking a small load will arc so little that you probably won't see it. Up the load while keeping everything else the same, and the arc gets bigger. But there's always an arc because the contact faces can't close infinitely fast.

This is why switches and relay contacts are rated at their maxmum SWITCHING current and voltage; defines how much load they can safely make or break without excessive damage to the contacts from arcing.



In a constant voltage (E) DC series circuit, when resistance (R) in one branch goes up, current (I) through that branch of the circuit goes DOWN - - Ohm's law. I= E / R , or in this case, E=IR - - as R increases, I has to decrease if E is constant.

85TIIDEVIL

iTrader: (2)

Ahhh.... I was thinking on the back end of the ignition switch where his wire was loose not the actual switching of the ignition itself. So it does make sense to shut down all accessories before shutting off and turning on the ignition over the 30-25 years it's been in use. I didn't see that point before.

And yep I screwed up. I jumped the gun in my thinking. I don't excercise my electrical theory much since school 10 years ago. doooh

But wait a sec:

^ Series circut... amperage is constant not voltage. My brain isn't in the mood to think this out. As long as Pele's point is cleared up in my mind I have a leg up for today.

85TIIDEVIL

iTrader: (2)

I apologize Drivin. I actually googled series and parallel circuts to brush up because it bothered me that I had to have such a brain fart to think out simple theory. Amperage is constant in a series circut "throughout the circut" but can be changed according to the resistance applied. Ohms law just like you said. Another dooooh for me.

DivinDriver

iTrader: (15)

No worries, compadre... can't tell you how many times I've punted that same one over the decades.

Amperage is 'constant' (as in 'the same regardless of where measured') throughout a DC series branch, is limited by the total resistance of the branch & available supply current, & is dependent upon the supply voltage.

Voltage across the entire branch is likewise "constant" in that increasing resistance of one series component increases the voltage drop across that one component & reduces the drop across all the others... but the total voltage across the branch doesn't change unless your supply saturates. Sum of supply voltage minus all voltage drops has to come out to zero.

So, when you have a crapped up switch contact & a fixed 12V supply, the switch starts developing excessive voltage drop across it, reducing what's available for the other components in series.

Meanwhile, since total branch resistance has risen, total current through the entire branch drops.

KansasCityREPU

iTrader: (9)

Sounds a lot like the theories we learned in BEE school in the Navy.

DivinDriver

iTrader: (15)

It should... I re-learned it in MCCES in the Corps, and then ended up teaching it there for a spell as well.

First learned it as a kid, dabbling with Heathkits and such. And I still get it wrong sometimes.

85TIIDEVIL

iTrader: (2)

Re-learning it sounds like something I would like to do. I think the first time around I was memorizing alot of formulas just to pass tests and get by instead of actually understanding the stuff throughly. A second time around I'm sure would be nice.

Next thing on the to-do list is to relay up my fuel pump. What Kentsu said, It's still stock wiring w/a Holley Blue and I definatly remember it measuring at 8.5V's last time I checked, definatly drops with power to the blinkers on, and is definatly loud. I hope it does indeed quiet it down. It couldn't hurt as a added precaution if I ever do get around to installing my n2o kit. Thumbs up to this thread.

etizz

i have a question in dealing with this diagram, from the 8 gauge wire to the 4-10 gauge wires do you just clamp em all together or did you use a block or what happened here, also what are the yellow wires that go from the red 10gauge to the 85 part on the relay? sorry for sounding stupid but i've had enough electrical problems with this car lol.

this can apply to headlights/power windows too right? and i can't seem to source an fc fuse block anywhere, can i use something generically bought?

Twilightoptics

iTrader: (1)

-Soldered with a 6 ga solder but connector.

The yellow wires are the wires that give the energize side of the relay power. When I clamped the 10ga terminal for the heavy supply side (red wire) for the relay terminal, I put an 18ga jumper (yellow) from 30 to 85. If you understand how a relay works it's not that confusing. Heavy power in and out that runs your device. Then you need power/ground to energize the relay. That's what the 4 terminals do. The engergize side takes very very little power. You could use smaller than 18ga I suppose, it's just what I had.

Yes, you can add relays to the headlights and PW. Since all the headlight power goes through the HL switch too. That's next on my agenda, but I'm going to go H4 or HID which most kits come with a relay kit. There's already a write up for adding relays to the PW. I forget if it's just archived or if it's in the FAQ.

I used a Mazda b TRUCK fuse box. Couldn't find an FC one myself.

Siraniko

iTrader: (13)

B-series fuse box is the same as the RWD 323; have less fuses than the FC ones.

Pele

iTrader: (28)

Additionally many of the loads in a car are inductive loads... Motors and such. (Anything with coils is an inductive load.)

Inductors resist change in current flow... That is, when the circuit is closed and current starts to flow, the inductor will try to prevent that current from flowing... However when you open the circuit up, it will try to keep the current flowing. Hence a much larger spark on an inductive load versus the same current resistive load.

Additionally, motors take lots of current on startup when they are not spinning. As they speed up from that dead stop, the current load goes down.

Lost of current on startup and the residual current flow when you shut it down equals lots of arcing.