Bouncing Voltometer?

[KDMatt]

This is a weird thing that happens intermittedly, and I'm wondering if someone can shed some light on this.

Usually when the car is running, the volometer will settle in to a reading between 13 and 14, but now and then, it'll erratically jump down to around 12.5 or so in consistent intervals. This is especially noticeable at night when my headlights are turned on because they will dim each time the volts spike down.

It only seems to happen when the car is idling which is leading me to suspect the alternator, but I'm curious if this could also be a connection thing too. Your experience is appreciated. :nervous:

[seerex]

I would first clean all your connections, alternator , battery and fuse box<especially the back> . Is your car idling at the correct rpms? Also see if any places will test you voltage regulator and alternator, free is always best. Usually this sort of thing is kinda normal in 240's but not in 280's . I would test and clean all you can to eliminate things.

[TomoHawk]

I agree that it's most likely assiciated with the voltage regulator. There's a relay inside it that opens & closes with the battery voltage to keep it up to correct volts. It sounds like for some reason under (higher amp load) that it cuts out, which is what drops the voltage reading, due to the headlamps being on.

[240ZX]

This is a weird thing that happens intermittedly, and I'm wondering if someone can shed some light on this.

Usually when the car is running, the volometer will settle in to a reading between 13 and 14, but now and then, it'll erratically jump down to around 12.5 or so in consistent intervals. This is especially noticeable at night when my headlights are turned on because they will dim each time the volts spike down.

It only seems to happen when the car is idling which is leading me to suspect the alternator, but I'm curious if this could also be a connection thing too. Your experience is appreciated. :nervous:

If this occurs at idle, it's likely that the RPM is just too low for the alternator to produce the required charging voltage. This is a common thing. Does the voltage come up when you rev the motor?

[richard1]

I have a 72 with the stock (remanufactured) alternator and a new voltage regulator.At idle, the engine is at 900rpm w/o a/c on. When the a/c is on the engine drops at 750rpm and the voltmeter is below the middle mark. the voltage comes up when the engine rev.

I am not a specialist of the electricals but I believe that the original alternator is weak for the work it has to perform and it can barely take care of a full load of accessories in same time as the a/c, lights and electric fuel pump.

Is my comment make sense for the 240?

[DatsunZsRule]

Above are all good suggestions. Cleaning electrical contacts,checking to see if the RPM is set correctly at idle which should be 800 @ idle on a manual transmission model.

Also go through and make sure all your electrical connections are connected good and not loose like at the alternator and battery cables ect. You can do this of course while your cleaning all connections. I'm willing to bet you got a loose connection somewhere in your electrical system.

Best of luck

[richard1]

You may be right and I will follow your advise to check the connections.

You are also right on a very important subject about clean electrical contacts: Spray cleaner products can save a lot of problems about electricals

The car has always been in Tenessee before I bought it and was a real time capsule.

I enjoy every moment I drive it.

[TomoHawk]

If you want to try spray cleaners, I would NOT recommend the ones you get at Radio Shack or local electronics stores. Those things just have solvents for degreasing that are harsh on the wires and connectors, and don't addreess the problem of corrosion on the connectors.

Instead, I recommend DeOxit 5 and 100. Use the 100% stuff (DeOxit 100) to get the corosion off, and the 5% stuff (DeOxit 5) to lube & maintain the good/cleaned connections.

DeOxit Info

[sblake01]

I guess everyone has their favorites. But use one that does not have silicone. I use the 'Tool Crib' products. Electric Motor/Contact Cleaner and 5 Way Corrosion Inhibitor & Lube used in the same way that Tomohawk mentions.

[DatsunZsRule]

"If you want to try spray cleaners, I would NOT recommend the ones you get at Radio Shack or local electronics stores."

What???? Dude, Radio Shack is where I got my Caig DeOxit stuff. If your local Radio Shack doesn't have it in stock then you can buy it on there website.

You'll get no argument from me though about Caig's product (DEOXIT) It's amazing stuff.

[TomoHawk]

Which DeOxit did you get? I'm talking about DeOxit 5 and 100 in the spray cans. I'll bet if you ask the guy at the Radio Shack about electric cleaners, he'll show you a can of tuner cleaner, or even WD-40. That's what you shouldn't get.

If Radio Shack has DeOxit, it's probably in the small bottles ( Vlike 20 mL) or you have to order the one you want.

[DatsunZsRule]

Yeah, I ordered mine over the computer on there site. I have a sh!tty Radio Shack store by my house Maybe you can't get the bigger cans there anymore. I don't know??? It was a long time ago for me.