posted 08/03/15 01:41 PM
What you need to do is rather simple, if we want to scratch the surface.
Grab an accurate amp clamp that will do DC volts, and hook into a quality multimeter.
Confirm the alternator is putting out low AC volts <.5-.75V AC, and that voltage is stable at the temp range
for which the regulator will be following, IE -20 is 15.4V, 75 is 13.8V.
Then you can move forward and with the engine running, perform the current test around the wire running from the alternator to the fuse block (hope I got the proper section to clamp on) and see what the base amperage will be at idle and corresponding voltage.
Now add one accessory at a time, noting the amperage and voltage at the battery. You can test this with individual circuits being engaged, to get a more accurate picture of what they may be drawing.
As things heat up in the engine bay, things may change.
After a long drive, things may be entirely different.
Batteries and wiring to accommodate trunk mounted installed, will change things a bit. Regardless of voltage sag or not.
Also, depending upon the efficiency of the alternator and control circuitry and the viability of the alternator power wires, this can all vary to some degree.
This is about as accurate as you are going to get, without removing and or powering up individual circuits with powered equipment to test what each component draws. Mixed bag of fruit.
I for one, would like to see where this thread is going. Combines well with what I need to know about my Colt's circuitry and accessories and what accessories are going to bring the amp/voltage threshold down to as things heat up. Then you can determine headroom based upon what happens when you full field the alternator. Current with your max number of accessories installed, versus accessories off and full fielding the alternator for maximum current effect, for a short burst - cold and hot, could be a good test, or am I wrong?
This may all get swayed slightly because manufacturers give a tolerance for max output, both at idle and high enough RPM to do the fielding test and produced maximum output, at idle, you won't get much, if half of advertised output from what I have been reading. Wish I had more to add concerning that ...
I want to know what my engine, headlights/taillights/markers, dash lighting and gauges will pull before 1 or more fans is added, and then there will be the clutch load of the AC compressor once things get rolling.
Much safer to know all the variables before determining what alternator to latch onto. I want some headroom for the reasons of wanting to have headroom and properly provide power to all accessories when they are on ... more so when the vehicle is rolling, but if most of the load can be accommodated while idling, the you won't be discharging the battery. The better the system is designed, the longer your batteries should like you and light bulbs, and not to mention your other delicate electrical equipement - ECU/TCU.
I'm half decided between a stock Mitsu 90A, or finding the 100A ... might be a wild goose chase for me (here in Canada, but yes, can import) on the possibility of the 140A as the wiring to support the 140A for any length of time (and hot engine bay wiring needing to accommodate a larger percentage in surface area due to heat reducing a wires capacity).
Just want to know I would have engineered something correctly, just the way a manufacturer would and have tolerance for most everything you normally throw at the charging system. I fully realize the manufacturers didn't design most older cars to be able to handle all accessories on, including defrosts and wipers, plus lighting ... for extended periods of idling.
C53A 1 of the ~1500
Posts: 1631 | From: THE Ottawa | Member Since: 03/05/05 | IP: (126.96.36.199) |