Voltage Gauge going nuts...

[Strongbad]

I think this is the proper forum for this.

Recently my volt gauge began dropping when the revs would slow down. It would be up around 14 when I was driving, but it would drop to the top of the red area when I would stop at a light.

Took it to the auto parts store, and they confirmed the Alt was not charging enough.

The alt was under warranty, so I got a new one for free. I put it on in the parking lot, and started it up, and it is still doing the same thing.

What else could be causing the volt meter to jump around like this?

Also, the plastic clip that snaps onto the back of the alternator broke off when I was installing it. Is there a way to replace that clip?

Thanks!

[haro1225]

Check all the battery cables for corrosion, that could cause the volts to drop too.

[ChilinMichael]

Yup, battery cables in our cars is a major causer of this. I'd go so far as to say it can accelerate other issues (such as alternator wear) because of heightened resistance and the necessity for overworking to keep the voltage up. Check both ground leads under your hood on both sides in front and clean those down, check both sets of terminals on the positive side, each side of the terminal and clean them down. Baking Soda should reduce/remove any acidic reaction on the terminal, I usually use a light Dremel wirebrush every month or so to clean them. make sure the terminal screw itself is clean, if not you can usually find a new one in a parts store for cheap, remember the positive side needs the longer one, negative is shorter. If you notice massive corrosion, try and see how the wire itself is (cutting back a small piece of the insulation can allow you to see it, do it carefully and reseal with electrical tape when done).

[Strongbad]

The battery is clean as a whistle, but I replaced the terminal screws anyway because one was a bit stripped. Problem still exists. At idle, volts are at the top of the redline (11 or 12 volts?). I turned on the lights, ac, and wipers and sat and listened to the engine. There is a loud, repetitive clicking sound, like a solenoid engaging and disengaging. Click, click...click, click....click, click...

I am stumped...

Any other ideas guys?

[ChilinMichael]

That "solenoid" may very well be your EGR, mine does that as well, normal as far as I know. The terminals that connect to the battery were clean I take it?

[Strongbad]

Perfect. No corrosion what so ever.

In the past I have had "no start" issues with the car, however after tightening down the terminal screws, it will start right up. That was why I replaced the terminal screws. Still no go. Voltage gauge is right above the red area when idling.

I would think I got a bad alternator, but they tested it before they gave it to me.

I will get under there tomorrow and trace the ground and hot leads back and see if they are perhaps loose on the other end...

[ChilinMichael]

There are ground points on both sides of the hood at the edges, if it's not raining tomorrow and you need reference pictures I'll be more than happy to take some. I'd recommend taking those off and cleaning them as the next step.

[Need For Steve]

hmm. my 2nd new alternator in a year is putting out low voltage. maybe it's something to do with this.

[Strongbad]

Pix would be a huge help Michael.

I took it to Autozone, and they said it reads "Low Output" and are willing to give me another one, but I really don't think the problem is the alternator any more.

Also I found a replacement for that connector clip that goes on the backside of the alternator. Maybe that will fix the problem. Perhaps the connection is loose without the clip.

We will see...

[ChilinMichael]

I'll be working on my car tomorrow, so I'll take some pics while I'm at it.

[Strongbad]

So I took it to an Autozone and a O'Riley. Both told me the alternator was bad. Low output.

So I went home and took it off, and took it to a different O'Riley and had them bench test it. It passed all three times they tested it.

So the alternator is 100%.

I told the guy at the store that the clip broke off on the connector, and he said that it might be moving around and causing a bad connection.

He sold me a GM replacement connector. It had three wires like this:

where as mine has only 1 wire. The guy told me I could just clip off the two other wires and it should work fine.

I went home and clipped off the broken connector near where it branches off from the rest of the harness, and wired the new connector to it. I noticed that the red wire is a much heavier gauge than the wire running from the loom.

I got it all wired back together, and no luck. Voltage gauge in the red.

I will take my amp meter out there tomorrow and get some readings to post...

[ChilinMichael]

Let me document mine tomorrow because one wire is for an external voltage sense, our cars don't come with it (00+ do) and if you hook it up to a proper 12v lead, you'll be holding 14v most of the time, I had this done in my car the first year I got it and I always run 14v. Our cars tend to hang at 13v or a little less otherwise normally.

[Strongbad]

I took this picture of my alternator connection. The wire was worn out at the end where it split off from the tree, so that was where I clipped it off.

Only 1 wire. Small gauge red one.



It's strange, because every replacement I find has 3 or 4 wires, such as this one:

[ChilinMichael]

Alright listen carefully folks, only gonna show you this once...

First, here are the two ground connection I spoke of you must clean under the hood. They are almost on the exact same spot on the fender on both sides:

Passenger/battery side:


Driver side:



Now, about your alternator. I'm well aware as I said before your car "stock" came with one wire, all of ours did. It's a universal pin setup for many GM's. The other wire you CAN hook into and use however, as I said before, is the external voltage sense.

Here's my pin configuration, you can see which ones are filled. Whichever one you don't have, is the external voltage sense one (I forgot which is which):



And here's the external voltage sense wire going into the main harness run to pick up the car's PROPER voltage (instead of the inaccurate reading the alternator does on it's own without this wire):


Yes, the picture it sideways, sorry.


Hope this helps...

[Strongbad]

Thanks for the pix. I took both ground wires off, cleaned them, and scrubbed them with wire brush before putting the back on nice and tight.

No go. Same low voltage problem.

I dug out my ampmeter and took some readings.

Battery (while off): 12.30
Battery (while on): 12.01
Alternator: 12.00

The first two are good. The second, while low, is not as low as it looks on the voltage gauge in the car, which sits at the top of the red zone.

I also checked the fuses under the dash. They are all working ok.

What else can I check?

[Archon]

What kind of shape is your battery in? A charged battery should read at least 12.6 volts. In order for the alternator to charge, it has to be putting out a higher voltage than the battery. You may have a combination of bad battery, and bad alternator.

[Strongbad]

The battery is probably a year old. Real good shape. No crust or anything. I have had the alternator and battery tested several times at competing auto parts stores. Each time they pass the battery and fail the alternator, however when I took the alternator off and had it bench tested, it passed.

[1995BonnevilleSE]

If the terminal are free of corrosion and the alternater is chargin the battery. Check the positve cable going to the starter I've seen the cable hit the exhaust manifold and melt the wire casing cuasing it to arch against the manifold.

[Strongbad]

If the terminal are free of corrosion and the alternater is chargin the battery. Check the positve cable going to the starter I've seen the cable hit the exhaust manifold and melt the wire casing cuasing it to arch against the manifold.

Interesting. I hadn't checked that. Will give her a look. Thanks...

[Wes]

If you measured 12v directly from the output of the alt, then your alternator is not charging at all. you are just seein battery voltage.