Voltage too high from alternator?

JakeRobb
03-15-2006, 10:52 PM
http://homepage.mac.com/jakerobb/camaro/questions/high-voltage.jpg
This looks high. My car sometimes charges at this level when the engine is cold.

Anything to be concerned about? Is it bad for the battery or other components? I've seen this in other GM cars... replacing the alternator (with the built-in voltage regulator) has had no effect.

96camaroSS
03-15-2006, 11:57 PM
I'd guess just by the gauge reading it's a little high. But I'd be checking voltage at the battery posts with the engine running to see exactly what you have. Mine always had a tendency to read like that when I hadn't driven it for a week or so. Battery would always be a bit low on charge.

If it always stays that high on the gauge and a DVM confirms more than 14.5vdc I'd say it's a problem. It'll cook the battery by overcharging it constantly.

If the true voltage is between 13.6 and 14.2vdc your ok.

littlbasterd
03-16-2006, 01:40 AM
test the alternator..looks a little high

JakeRobb
03-16-2006, 06:45 AM
Moving soon, my DMM is buried somewhere in a box right now. I'll test it soon.

I've only ever seen this problem on GM cars, but I've seen it on three others (Achieva, Bonneville, Regal), and on each of them, the DMM read out pretty much exactly what the car's gauge indicated. Has anyone else ever seen this?

shoebox
03-16-2006, 07:25 PM
Just after you start the engine the alternator is going to put out the most voltage, because it is trying to replenish the battery from using the starter (the largest single drain on the electrical system). It should go down a little after a short time.

JakeRobb
03-17-2006, 08:03 AM
Okay, found the DMM, hooked it up to the power outlet in the car and watched it while I drove into work this morning (15 minutes).

Right when I started it, the gauge went up to where it was in the picture above. The meter read 14.9v. Over the course of the 15 minutes, it slowly dropped to 14.2v.

If I interpret the gauge as linear, that line should be 15.5v, which is why I was worried. It's not. It's more like 14.7.

In the other cars I mentioned, I've seen as much as 16.5v.

LiENUS
03-17-2006, 08:28 AM
Unfortunately our guages aren't all that accurate this is normal...

MasterEvilAce
03-17-2006, 08:30 AM
The gauges aren't the best.. I've had mine go from a hair over 13, to the line to the right of 13. I've also had the fuel gauge beat to the music if there's a certain amount of gas in the tank.. it just gets confuzzled

JakeRobb
03-17-2006, 08:30 AM
I'm a little surprised -- my Z28 is the first car I've ever had with an accurate fuel gauge, and the first car I've ever had with an inaccurate voltage gauge. :shrug:

MasterEvilAce
03-17-2006, 09:32 AM
lmfao. all the fbody gauges suck. Really really hard.
speedo is the only actually accurate gauge. the rest are all "proximity"

96camaroSS
03-17-2006, 05:12 PM
How do you know for sure that the speedo is even accurate? :D

MasterEvilAce
03-17-2006, 05:43 PM
How do you know for sure that the speedo is even accurate? :D
speeding ticket

JakeRobb
03-18-2006, 08:04 AM
I can take the RPM indicated on my tach, do the math to calculate my expected speed based on my selected gear, rear end gear ratio, and tire size, and see that that speed matches up with my speedometer. It always matches, dead on.

The odds that both gauges would be inaccurate by the same amount are extremely low, so I figure they're both accurate.

From what I've heard, most F-body tach's aren't accurate at all -- guess I got lucky.

LiENUS
03-18-2006, 08:21 AM
lmfao. all the fbody gauges suck. Really really hard.
speedo is the only actually accurate gauge. the rest are all "proximity"
According to my gps my speedometer gauge is about 5mph fast.

MasterEvilAce
03-18-2006, 08:23 AM
According to my gps my speedometer gauge is about 5mph fast.
According to your speedo, your gps is 5mph slow.

96camaroSS
03-18-2006, 11:18 AM
speeding ticket

Ouch!!! :D

GreenDemon
03-18-2006, 11:29 AM
On newer f-bodies (97, 98+?), I think the gas gauge is computer controlled to compensate for the shape of the gas tank. On the older ones, of course, 1/2=1/3, and gets worse the lower you go, at least on mine. It'll sit above full for quite a while and then start to drop like a rock.
My speedo is dead on, the tach is 100 rpm high, temp reads 10-30* high depending on where it is, haven't verified voltage though.
Most of the gauges do suck, but when you have the car long enough you know what's going on anyway.

You shouldn't be worried about a high voltage reading on startup, unless it pegs in the red or it stays that way all the time. 99% of the time the only problem you'll have is when the gauge drops too far to the left and stays there...