Erratic volt gauge

[Pomorza]

Hey guys.

In the past couple of weeks I've noticed that my volt gauge is not stable when I'm driving. At idle it sometimes jumps a bit (to the left and right). When I drive it does evens out but sometime it'll jump up to 16+ and then back down to where it should be. Any ideas?

Jan

[sblake01]

Could be any number of things. Bad guage, bad connection(s), failing voltage regulator. You'll need to run some tests.

[Gary in NJ]

Place a multimeter on the output of the alternator and see if the readings are equally erratic. If so, the problem is most likely a bad regulator. If the reading is smooth, the problem is your gauge or the wiring leading to the gauge. It could be as simple as a loose connection.

[sblake01]

Isn't that what I said?

[Gary in NJ]

Isn't that what I said?

I just used more words;)

[Pomorza]

Ok so I need to use a DMM on place it on the alternator output to the battery? Sorry I'm familiar on how alternators work just not on how the wires are set up.

Thanks

Jan

[SteveJ]

You likely have a wire going to a post on the alternator that is covered by a rubber boot. That is your positive. For the negative, go to ground.

[bobc]

If you search the archives you should be able to find some info on this as it comes up from time to time. One post I recall was similar to the problem I had with my original Z many years ago and sounds similar to your problem. Somewhere there was a loose ground connection that was causing the problem, but I just could never find it. This poster in this case added a ground cable directly from the alternator and it solved the jumping ampmeter problem

[Gary in NJ]

This poster in this case added a ground cable directly from the alternator and it solved the jumping ampmeter problem

The 280's have a Volt gauge, not a ammeter like the 240's.

[Pomorza]

I'm pretty sure it is the regulator but you guys tell me to make sure.

I connected the positive to the one screw on the alternator with the wires going to it (with the black cover) The ground wire I connected to the ground on the on battery (+).

With the car running (lights off) the DMM read roughly 13.25 but was very very erratic (dropping up and down .5 volts). When I revved the car the it continue rising up to and maxes out at 15.5 volts.

With the (lights ON) it idles at roughly 13.1 volts again rather erratically. When revved (to 3k maybe) it hits 14V roughly.

Again all the readings were very erratic so getting a good reading was hard to to do. Hope this is enough to let you guys know what it is.

Jan

[SteveJ]

At this point, I'd consider replacing the alternator and regulator. Also, check your headlight and parking light circuits from the switch down to the fusebox. Corrosion can cause the system to consume more power. (Essentially you're adding resistors to the circuit when you have poor or corroded connections.) It's scary to see the effects of 30+ years of use on the circuit. I've seen connectors almost melted. I've also had a fusebox melt down. If you're driving the car at night, especially with the days getting shorter, you owe it to yourself and to your Z to take care of the lighting.

By the way, while Dave (Zs-ondabrain) doesn't offer a headlight relay harness for the 280Z, you may want to check to see if he will do a cleaning on your combo switch.

[Pomorza]

At this point, I'd consider replacing the alternator and regulator. Also, check your headlight and parking light circuits from the switch down to the fusebox. Corrosion can cause the system to consume more power. (Essentially you're adding resistors to the circuit when you have poor or corroded connections.) It's scary to see the effects of 30+ years of use on the circuit. I've seen connectors almost melted. I've also had a fusebox melt down. If you're driving the car at night, especially with the days getting shorter, you owe it to yourself and to your Z to take care of the lighting.

By the way, while Dave (Zs-ondabrain) doesn't offer a headlight relay harness for the 280Z, you may want to check to see if he will do a cleaning on your combo switch.

I may indeed check all the electrical work to the car. None of the fuses (other than the A/C one) has ever reached a temp higher than what I would like it to, that being hot or something. I am running aftermarket headlights (H4 replaceable bulbs to be exact, 55W I believe) so I can see how it can draw more power than the stock ones.

What is the best place to get alternators/regulators. There's a place here in Tucson that rebuilds alternators which I'm considering instead of getting new one.

Did forget to mention this. I replaced all four of my fusible links about a week ago as one of them broke in my hand (literally). I bought replacements from MSA and they seem to work great. I believe I have a green two reds and a black. I don't know if this makes a difference to my Z's issues.

Thanks

Jan

Edited September 4, 2010 by Pomorza