Electrical charging system question, Alternator? Options

[rjames]

I installed a brand new battery and a new voltage regulater last week in the car. My volt meter is showing 12.5 volts at the terminals. With the car running and the lights and fan on my volt meter fluctuates between 12.7 and 12.9, then slowly starts to dip, getting as low as 12.5 before I decided to shut the engine off because I could see that the battery was slowly draining.

Would it be logical that the alternator might need replacing? The alt. belt also seemed tight (not sure exactly how tight it should feel though.) I can check the electrical connections (have to find them first though.) The connections at the battery all look good though.

It doesn't look like a fun job to replace the alternator, but I'm up for the challenge. Anything else I should look for before I go this route??

Thanks!

PS: Forgot to add that the alternator light on the dash comes on when starting the car, but goes off right away once it's started and doesn't come back on at all when driving.

[jk76.914]

Hi Robert,
Well, I finally got a chance to get some pictures for you on the relay installation on the volt meter. I'm afraid the pic doesn't show much in the way of step-by-step, but it's pretty straightforward.

1. You can basically pick ANY relay. Just make sure it has a 12v coil. Radio Shack has a couple that would work for short money. The contact rating is unimportant, as you'll only be switching a few milliamps of current at most- just enough to energize the coil in the meter itself. The one I got was actually too small to handle easily, and I would go for a bigger one it I had it to do again.

2. You take the two wires that originally connected to your voltmeter and connect them across the relay coil. If you can dig up a relay that has 1/4" tab connections, they would plug on directly! (RadioShack #275-226 ($6.49) would work, even though it is rediculous overkill in terms of contact rating, which is OK.) Now, when the ignition is turned on, it energizes the coil and closes the relay's contacts to complete the circuit to the volt meter. And, when the ignition is off, the circuit to the meter breaks, so you don't drain your battery. See schematic below...

3. The hardest part of the whole job is running a new wire from the battery + terminal to the console. I ran mine before my interior was in. I drilled an oversize hole in the firewall, and ran a wire through it, protected by a rubber grommet that I got at the hardware store. You MUST run a new wire and dedicate it to the voltmeter, or the meter readings will be affected by voltage drops caused by whatever other load you have hanging off the same wire. In the console, this wire connects to the switch inside the relay. All relays have pictures on them somewhere showing which terminals are for the coil, and which go to the switch.....

4. Easier, but still important, is running a new ground wire. I ran mine from the forward-most 6mm bolt that holds the console's heater lever to the top of the tunnel. First I removed the lever and polished up the surfaces on the tunnel and the bottom of the lever with a wire brush. This also will help make sure you don't have any grounding problems with the rear blower fan..... Then I reinstalled the lever and the rear bolt, and finally installed the front bolt- with its new ring lug sandwiched between two internal-tooth lockwashers under the bolt head- and that was it. The other end of the new ground connects to the ground terminal on the voltmeter.

5. Last step- connect a wire from the other switch connection on the relay to the + terminal of the voltmeter.

And that's it! You will now measure voltage directly at the battery terminal. When you turn on your direction signals, you won't see the needle dancing anymore! And, you can see the effect of load and RPM on charging and the battery. Much more useful than measuring voltage drop across all the wiring and connectors between the battery and the load.

I'm rebuilding my tach right now, but when I get it in and I'm driving again, I'll take some photos of the voltmeter under various load and RPM conditions, and add them in here as well.

Have you made any progress on yours?

regards,
Jim