Just recently, my voltage gauge went from reading 13 at idle to a few notches lower when running. With lights, AC, wipers etc on, it'll get down into the yellow easily. I've had the battery and alternator tested at three different parts stores and all have verified that it's charging and cranking fine. Should I be concerned or is it probably just the gauge? I get the famous alternator belt squeal starting up cold every morning but that's nothing new. I don't want to bother throwing money at a new alternator if it's just a faulty gauge but is there anything else I can check? Thanks!

 

The gauges in 3rd gens are notorious for their inaccuracy; most only provide a suggestion rather than solid info. With a multimeter, you should read 14+ volts across the battery terminals with the engine running at operating temp; if not, there's a problem either in the alternator or it's associated wiring/connectors.

Fix the squealing alternator belt; it shouldn't be making any noise at all. It's likely glazed from age and underhood heat, and needs replacement. While you're at it, inspect the pulleys for nicks or other abrasions that could damage the new belt.

 

Reads 14 at idle no problem - it's just concerning because this problem popped up out of nowhere and I really don't want to go messing with the bulkhead connector if I don't have to just to fix a faulty reading.

I'm not sure what it is, but I've replaced that belt three times in three years and sooner or later they always start slipping on a cold start up. I've thought my pulleys might be out of alignment causing wear and tear on them in the past but I've honestly never bothered to check since I end up chucking a new one on there once it gets unbearable. Then again, I'm usually buying parts-store belts.

While we're on the topic, what belts are people using these days? Years ago, everyone swore by Gatorback belts, myself included, but those seem to be harder to find these days.

 

All of those accessory loads draw VERY high current, which travels through all manner of wires connectors and fuses under the hood and through the firewall and under the dash (including the ignition switch), all of which have resistance, which creates voltage drop, which of course increases as current increases (Ohm's Law and all that, you know).

The Volts gauge is affected by that. It is connected to the electrical system far enough downstream that the voltage at the point that it "measures" is often considerably lower than the voltage at the alt output or batt terminals.

If it seems to be more heavily affected by accessory loads than it once was, it's probably because something in all that convoluted pathway that feeds everything, has changed. Could be things like a fusible link or a wire with broken strands; a connection such as C100 getting some corrosion; some "improvement" that somebody has made to The Big Red Wires, such as cutting and splicing; ignition switch contacts getting worn; and so on. For that matter, you might want to try just unplugging and replugging C100 to scrape the terminals a little bit. Maybe look at it while it's apart and check for anything overheating, especially either of The Big Red Wires. You can also probe the system at each convenient point along the distribution chain to see if there's lots of voltage drop at any particular one.

Your belt slipping is probably because the tensioner is weeeeeek. Replace it. Keep its pivot lubed.

Belts are a commodity as far as I'm concerned, at least, among the major brands. Goodyear, Dayco, & Gates are all perfectly OK. Not the sort of thing to get worked up about.

 

I'm absolutely going to check the C100 since absolutely nothing has changed within the last week this has started but I'm sure once I crack that'll, it'll be full of crust and goo.

On the matter of belts, I'm not running a tensioner - just the a carb V-belt system. I've never been able to get my alternator any tighter than "hand tight" which will be good enough for a while until the squeaking inevitably begins a few months later. I'm not aware there's any way to fix that, is there?

 

If you're seeing 14 volts, your charging system is OK. If your only symptom is a low reading on the dash gauge, it's probably the gauge; any device with moving parts is subject to wear over time.

Three belt changes in three years is at least two too many. If you aren't buying Gates or Dayco belts, make one of those your next one. No-name auto parts (or even 'name' ones these days) are quality-suspect. And while anything is possible, unless the mounting hardware on your alternator, etc., has loosened, it's not likely the pulleys are mis-aligned. If you have doubt, lay a large straight edge across them and give them an eyeball inspection.

 

That would be a major problem right there. Nowhere near enough belt tension.

​​​​​​​Yes of course there are ways to fix that. By actually tightening it, no less. A tire tool through the big hole on top of the bracket works great.