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Alternator requirements w/ac |
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bigbad69 
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Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6212 |
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 Posted: Apr/01/2023 at 1:34pm |
The current capacity (sometimes referred to as Ampacity) of copper wire is determined by heat rise. All wires have resistance. As the current increases, the power dissipation within the wire increases. The dissipation is in the form of heat and all wires will heat. It is the amount of heat that can be tolerated that determines the current capacity of the wire. If you are adding extra loads to the electrical circuits, then you need to distinguish between peak and average power. Starter motors can draw in excess of 200A, but you don't need a 200A alternator because the starter is not used constantly. Over time, the alternator will replenish the charge used by the starter motor. Things like EFI and electric fans can add significantly to the average power required, High output audio systems add significantly to the peak demands, but not the average demands on the battery and charging system. EFI runs constantly (hopefully) and the solenoids are current hogs. Throttle body injection has 1 or 2 injectors vs. port injection which has 6 or 8 injectors. If adding EFI, you need to consider the added current load and its affect on the the wiring harness. The manufacturer should provide current load spec's for their system. Electric fans are also current hogs when they are running. If you have the fans running constantly, then it is a factor in the requirement of the wiring harness and charging system. If you a circuit which shuts down the fans when not needed, then the load on the electrical systems drops. My point is, there is no one size fits all answer when adding new electrical components to your car. Do you need to upgrade the alternator or wiring harness? Well that depends upon the modifications you do.
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69 Javelin SST BBO 390 T10
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73hornut
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Joined: Jul/03/2007 Location: Southern Oregon Status: Offline Points: 3055 |
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Posted: Apr/01/2023 at 4:36pm |
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I run a cs140, which holds 14v at idle with AC and electric fans, the cs130 would drop below 12v and continue down while sitting at idle in 114 degree days, which made the ac much less cooling.
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71 Javelin
74 Gremlin 79 Spirit AMX Rogue Valley Rumblers Like Us on FB https://www.facebook.com/groups/1602825606650796 |
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FSJunkie
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Posted: Apr/04/2023 at 4:36am |
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All you alternator guys whining about voltage drop at idle...
Meanwhile, those of us with GENERATORS:
 This your first time, huh? |
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'66 Marlin
'72 Wagoneer '73 Ambassador '77 Hornet '82 Concord D/L '84 Eagle Limited |
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farna
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Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19075 |
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Posted: Apr/04/2023 at 9:02am |
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A 55-65A alternator is fine with AC and electric fans. I run a 65A 10si on my car with 4.0L. Electronic ignition (all the Jeep donor stuff), AC, Kenwood stereo (no external amp though), halogen headlights, Ford Contour dual fans (previously ran a single Taurus fan, had to switch to Contour setup when I went to a thicker radiator). Been running this for 20 years with no issues. You do have an up to 80A surge for maybe a second when the fans start, but the battery handles that. The fans don't draw that much once running. |
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Frank Swygert
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JGRANTAMX
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Posted: Apr/05/2023 at 8:00am |
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My 70 Javelin has AC FI variable speed controlled electric fans and a sound system with an unknown amplifier nothing crazy, I have the stock 55 AMP alternator. From reading this thread it seems I might want to upgrade to the alternator listed by Trader, does that alternator have an internal voltage regulator and do I have to make changes to my stock wiring or Motorola voltage regulator?
J
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Mopar_guy
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Posted: Apr/05/2023 at 9:28am |
IMO I think you’re just fine. DMack has the same setup and doesn’t have problems. If you’re not having problems, why change it just to change it??? It’s a solution looking for a problem.
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Trader
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Posted: Apr/05/2023 at 9:40am |
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The CS130 and CS144 both have internal voltage regulators. You will want to also get the wire connector available almost everywhere.
There are wiring diagrams that incorporate the factory voltage regulators also for GM that you can find online. No reason, if you wanted to, connect the Motorola regulator. You will have to figure out the wiring as none were found posted. Should be easy enough though, just get a colored pigtail and not one that has all black or all white wires. Terrible things if you make your own wiring diagram which is highly recommended.
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JGRANTAMX
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Posted: Apr/05/2023 at 11:46am |
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I am still assembling my Javelin wiring will be done in the next few weeks, if it's a fairly simple conversion I will change up the alternator if I have issues.
Thanks J
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farna
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Posted: Apr/06/2023 at 7:50am |
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People think about the total amperage draw then think they need an alternator that puts out that much. Most of the draw is temporary though. The fans may draw 60-80A on startup -- for about half a second (maybe a whole second). You don't need 160A of alternator for that. When continuously running Contour fans (both together, not each) draw 25-33A. That's what you figure in your alternator calculations. Then what everything else draws AFTER STARTING. The battery provides the buffer for the very short surge when starting (which is 120-135A.. again, when both start at the same time, or 60-70A each). You can further reduce the surge by having them both start at separate times... either with separate controls or a delay. They were originally wired for both to come on at once, first at a low speed then bump up to a higher speed (amp draws here are on high). There isn't much (if any) surge when going from low to high since the motors are already turning. See https://www.vintage-mustang.com/threads/contour-dual-fan-amp-draw-real-data.906361/ Same with your house electric box. Typical boxes are 200A, but if you add up all the breaker values you'll find 300-400. You don't have everything plugged up and running at the same time! Main consideration is the things that DO run a lot and have big draws, like the HVAC system. I recently had to wire a detail shop equipment room and had to assume everything could be running at the same time for the sub panel. Wouldn't happen often, but it could, so had to get a panel rated accordingly. |
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Frank Swygert
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Trader
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Posted: Apr/06/2023 at 8:20am |
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Believe what some run into is not the alternator total output, but the output at idle.
None of these alternators put out full amperage at idle. Neither did generators. The factory Motorola did a better job of it then the 10SI or even the 12SI. The CSxxx does a better job of it then the Motorola and far better then the 10SI/12SI's. People drive in different places and if they are doing a lot of stop and go driving, with a stereo, fans, air conditioning ... they likely notice the voltage drop. A couple of days city driving may not even charge the battery. Driving now is different. Higher highway speeds and many, many more town and city stop lights. If I lived in the city, my car would be an automatic by now also!
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