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Wiring Harness
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59 in Calif
Posted 2015-08-27 2:53 PM (#488130)
Subject: Wiring Harness


Elite Veteran

Posts: 1102
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Location: Hayward, Calif
Hey Guys, 59 Chry, I'm checking out the circuits on this dash/wiring harness. I have a 12 ga wire from batt terminal on Ign switch going to the lite switch, which is connected to another 12 ga wire going to the volt reg, which makes this a constant hot circuit. The wiring diagram confirms this circuit. I just don't remember the volt reg having a constant hot terminal. So if I understand this correctly, when the gen is working the reg sends that amp's to the lite sw to the ign sw to the batt. Now I'm wondering if those 12 ga wires are going to handle a 50 amp alt. If I use a 35 amp alt. I don't think it will carry the draw from the A/C at eng idle speed. What is an ISO relay ? What does ISO mean ? Opinions at this point are welcome. Thanks, Jerry



(dash wiring 001.jpg)



(dash wiring 002.jpg)



(dash wiring 003.jpg)



(dash wiring 004.jpg)



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Attachments dash wiring 001.jpg (131KB - 110 downloads)
Attachments dash wiring 002.jpg (130KB - 106 downloads)
Attachments dash wiring 003.jpg (133KB - 142 downloads)
Attachments dash wiring 004.jpg (144KB - 122 downloads)
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ttotired
Posted 2015-08-27 7:33 PM (#488147 - in reply to #488130)
Subject: Re: Wiring Harness



Expert 5K+

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Location: Perth Australia
I saw in the other thread why you asked about an ISO relay

He means an isolation relay, basically, you use a relay like the start solenoid (here we call it a continuous duty solenoid) that you run one wire from the
battery + (or the start solenoid) and power all the non original loads directly off that

That relay/solenoid can be turned on by a separate switch or wired to your ignition, whatever

It is a way of adding another heavy power supply into your car without cutting up the original wiring

Still needs to be fused though:)

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jimntempe
Posted 2015-08-27 7:49 PM (#488149 - in reply to #488130)
Subject: Re: Wiring Harness



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Location: Arizona
<p>Not entirely sure I understand your question but if you aren't adding anything new that draws power thru the exiting harness it's not going to draw more power than it even did no matter how big an alternator you put on it UNLESS something shorts out. However, the part of the underhood wiring that feeds power to recharge the battery WILL draw more, when the battery is significantly discharged, if you put a bigger alternator on. That's the part of the electric circuit you may want to beef up, that underhood part that handles power TO the battery from the ALT. If you want better protection to the original circuits inside the car put a fuse (or fusible link) under the hood in the line that feeds main power to the inside harness. If you are adding AC I would not power the A/C from the original harness but would run a new circuit for it. When I added AC to my Dodge I ran a new circuit from the battery to the A/C Input Lead with a relay to control it. The relay turns on when the key is turned on. I also put a circuit breaker in the new circuit.</p><p> </p><p>An ISO relay is one of the little square relay with spade terminals sticking out.  Here's a blue one... http://www.ebay.com/itm/like/151658527555  If you did like I did you want one with the terminals for turning things ON when it's powered.  Some come with terminals for both, some with only one or the other (on versus off) terminals.</p>

Edited by jimntempe 2015-08-27 7:56 PM
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LD3 Greg
Posted 2015-08-28 12:02 AM (#488164 - in reply to #488130)
Subject: RE: Wiring Harness


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Location: Ontario, Canada
It has already been pointed out that with an alternator you won't need the wire from the old reg to the ign/light switch. You simply run a new charge wire from alt to the bat. This won't overload the old harness at all regardless of the new alt output.

The only significant additional current draw from an A/C system is the extra high speed blower motor. The original wiring is perfectly capable of handling this common option.

Who cares if there is a mild discharge at idle?!! I kinda thought that was one of the reasons cars even had batteries!! You know, to take up the slack in low generator output situations!

People like to cite the story that headlights will dim while idling. Again, who cares? Nobody needs full headlight brightness while idling at a stop light!!

Greg
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rushpowersystems
Posted 2015-08-28 2:06 AM (#488170 - in reply to #488130)
Subject: Re: Wiring Harness


Extreme Veteran

Posts: 524
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Location: West Jordan
I care.

Yes run a larger cable from the alternator to the battery but install a fuse on that line within one foot of the battery. I would run at least a 10 gauge but in my systems I run larger than I need, so I would use an 8 gauge. Go one step larger on your fuse, 50 amp alternator needs a 75 amp fuse, alternators make more power when cold.

OK I get that we are not talking about a daily driver so this is just educational so you can make an informed decision on your system.

When you come to a stop light and your alternator can’t keep up with the load at low RPM you will run off the battery. Generators are slow lumbering beasts, alternators react much faster. So when you discharge your battery at an idle because the alternator cant product enough power, when you step on the gas the alternator will full field or come close to it. Full fielding is when the alternator produces its max power output. That generates a lot of heat and by the time the alternator has recharged the battery you are stopping at the next light. So on a hot night the alternator never has a chance to cool down because it is always trying to catch up. when an alternator over heats the gap between the rotor and stator expands, when that happens the electro mechanical pull is not as strong so the alternator produces less power. So the bottom line is on a cold night it may be no big deal but on a hot summer night it is.

I am not typing this by candle light, I have a lamp on, and I have a lamp on because Tesla bothered to build something better. And since an alternator is basically what Tesla invented, there is no reason to put up dim lights at idle. In a vehicle the alternator is there to power the vehicle, the battery is there to stabilize the voltage and start the car, not power anything with the engine running, if you do so it will shorten the life of the battery and the alternator.
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59 in Calif
Posted 2015-08-28 10:59 AM (#488194 - in reply to #488130)
Subject: Re: Wiring Harness


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Posts: 1102
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Location: Hayward, Calif
OK Guys, I think I'm getting a handle on the whole electrical thing. Seems no matter what questions I ask I'm coming up with the same answers. And I appreciate everyone's imput on this. I'm restoring this car for the wife so am being a bit over cautious. Once I get the eng reinstalled I can run the alt. and A/C wiring at that time. So once again a big Thank You for all the help. I'm hoping next year this time this car will be at the paint shop. Jerry
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57chizler
Posted 2015-08-28 3:10 PM (#488209 - in reply to #488194)
Subject: Re: Wiring Harness



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The ability of a certain gauge wire to handle a certain amperage is dependent on the wire length; in the case of 12 gauge, 10 feet or less will handle 50 amps.

There is a misconception about alternator amp ratings; just because an alternator is rated at, say, 35 amps doesn't mean it maintains that output throughout the rpm range so upgrading to a higher amp alternator doesn't necessarily provide more power for accessories at low engine speed. That's why it's wise to purchase an alternator that has its output at a lower speed and these generally aren't the typical Mopar round back/square back offerings.
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jimntempe
Posted 2015-08-28 11:25 PM (#488241 - in reply to #488130)
Subject: Re: Wiring Harness



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Location: Arizona
A couple of alternator graphs. Ones for a common chevy and the other is a hi output ford. Note that for the hi output one that even at idle (alt speed of 1500) you get at least 40 amps. For the old style but pretty common 10SI rated at 63 amps you would get about 20 at idle. You can also see on the Ford graph what rush mentioned, how the power output varies with temperature. At high speed when really cold its 110, really hot is 90 amps. Both are a lot better then that old generator that's disconnected by the cutout at idle speeds.



(10 si alternator performance curve.jpg)



(ford 110 amp alternator output chart.jpg)



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Attachments 10 si alternator performance curve.jpg (47KB - 122 downloads)
Attachments ford 110 amp alternator output chart.jpg (51KB - 112 downloads)
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rushpowersystems
Posted 2015-08-29 12:29 AM (#488254 - in reply to #488130)
Subject: Re: Wiring Harness


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Posts: 524
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Location: West Jordan
FYI, that’s not engine RPM, its alternator shaft speed. So 1600 alternator shaft RPM is about 700 engine RPM depending on crank and alternator pulley sizes.
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jimntempe
Posted 2015-08-29 12:50 AM (#488262 - in reply to #488130)
Subject: Re: Wiring Harness



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Location: Arizona
I know. The graphs are clearly labeled. One says Generator shaft RPM and the other says alternator speed (rpm). Which is why, in my post, I said engine idle speed would be roughly an ALT speed of 1500. The numbers I suggested as typical idle output were then pulled from the graphs at 1500 rpm ALT speed.
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