1) It's fine with either the fan or the a/c running, just not both, which is what my original post pertained to. Mechanical clutch fan moving more air? Maybe, but they also absorb more horsepower. Not a big problem for the boulevard cruiser but for a street/strip car we cherish every little edge we can get. 2) Thanks, I'll look into this, although I have pretty much decided to go with a 12si alternator and heavier wire at this point. 3) The a/c works great before the fan kicks on, at which point the voltage drops quite a bit. 4) I am measuring the voltage at the battery. 5) Power for the fan comes from the battery. 6) Yes, I'm sure a new harness should be in order and I know that they are not difficult to install, but there are circumstances that prohibit me from being able to purchase an over the counter plug and play engine harness, so I would either have to build my own or modify an original type harness. Bill
I just took a look at the MAD Enterprises website and some of their products and tech features. Great stuff. I'll read more on it when I get more time. I'm sure I'll be putting some of this information to good use in the future. Bill
Have you had luck in installing a larger charging wire? I have this same problem on my 70 chevelle, all I'm running is MSD ignition with a 100 amp powermaster (8002) alternator, 14.4 volts no problem but when the fan kicks on it drops to 11.8 ish. It's been suggested that I upgrade the 10 or 12 AWG alternator wire to 8 AWG. I was thinking about running that to the junction block then adding an additional 8 AWG wire to the battery. Look forward to hearing your results!
Some belated comments, just spotted this thread. Don't think any of this has been suggested already, so hope I am not being Captain Obvious here: *) Even #8 wire is on the thin side for an 100A alternator. If you really do draw 100A through a 3ft piece of #8, you will loose about 0.2V (20W). By the book one should use #6 or thicker for 100A chassis wiring. *) Check for bad connections in your connectors in the high current circuits. Let the car run in idle with the hood open for a few moments with one of the high loads, like the A/C, running. Shut engine plus accessories off and then check wiring connections/connectors in engine compartment with pinky. Remember your numerous grounding straps. :Smarty: If any of them are noticeably hotter than the connecting piece of free wire, then you may be loosing quite a lot of power there. This can be a serious problem with older wiring with crimped connections and oxidized bolts, much more so than thin wiring. I always soft solder lugs and connectors in addition to crimping to avoid this problem. *) You may not be able to achieve running everything and the kitchen sink in idle without running the battery down. As was already mentioned then alternators usually only reach full charging current at 6000 alternator RPM, which is normally around 2000 engine RPM (3:1 pulley ratio). At idle you will be looking at less than half of full current, so headlights, A/C, fuel pump and fan may be asking for too much even with perfect wiring and a large alternator. *) The electric fan is only an advantage in racing if your engine and climate allows you to race with it temporarily shut off. If you have to race with it running, it will cause more drag than using a clutch fan, as the alternator has to generate enough power to run it. Converting power from mechanical to electrical energy and back to mechanical is almost certainly causing more loss than just simply using a simple clutch fan, which starts to slip at high engine RPM anyway.
This all sounds like good advice to me. I tried your suggestion and ran the engine with everything on for about 2 minutes, shut it off and checked the ground wires. No warm ground wires anywhere that I could find. I've been looking at the MAD Enterprises website. I like their ideas and plan to go that route when I get another chance to work on my own car for a change. Thanks. Bill
does the clutch fan slip at high rpm or when it gets to a certain temp? I thought it was purely temperature controlled
Both it's a fluid coupling with an additional thermostat to control intenal baffleing, that is, if you use the heavy duty one.
