Amp gauge / Efan, charging or not?

[Kyle]

Hey guys-

I have a stock electrical system in my 72 240, with the addition of an electric fan. The amp gauge sits at ~10A when running, goes to ~30A (on a 45A gauge) when the EFan kicks in.

Tuesday, I was out driving in stupid heat, and the fan ran the whole time (as did the AC, heh heh).

Now, when the car is running (fan off) and the battery is partially discharged (from idling with the fan on, or starting up, etc.) the gauge shows about ~20A. When the fan comes on, it DROPS to about 10A.

Basically, it's behaving like the alternator can put out only 20A now, and if I try to ask for more, it goes into limp mode, dropping to 10A. Does that make sense? What should I look at as far as culprits go? Is 30A too much to draw off the stock alternator continuously? Should I just install a one-wire 100A alternator and be done? And if I do so, will the stock amp gauge still work?

So many questions....

[Bambikiller240]

Kyle:

I'd pull the Alt and battery and have them both checked at a parts store first.

If you have to upgrade Alternators, I'd go with a internally regulated ZX unit rather than a GM "one-wire" unit. It won't get you as many AMPS out, but it is doubtful that your wiring system can safely handle 100 AMPS anyway. There is a Technical Article about the ZX Alt upgrade in Tech articles forum if you decide you want/need to go that route.

BTW, I have a friend who switched to a GM one wire alt in his Toyota truck and he's been replacing the alt at least once a year and has had wiring meltdowns several times over the past 3 years.