Different voltmeter readings? Options

[SKL1]

I've noticed with my '71, which has about 120K miles on it, the voltmeter is pretty much always reading around 11 V regardless of speed or revs.

In my '73, which has about 77K miles on it, it reads 11 or so at start up and for the first couple miles and then goes up to between 12 and 13.

I swapped the voltage regulators for the heck of it and it didn't change anything. Is the older alternator from the '71 just worn out?? Not looking forward to changing it with the engine in the car!!

[Spoke]

The dash voltmeter on my '71 reads between 12-13.5V. The dash voltmeter is far away electrically from the battery to give accurate readings. You should check the battery voltage with a DMM.

Does the GEN light come on with key-on and go out when the engine is started?

[emerygt350]

That dash volt meter is great for reminding you the blinker is on, and that's all. I put a relay in and wired mine direct to the battery. Now it is useful. The original wiring to the meter now turns on the relay which brings fused 12v direct (more like 13.7 when the car is running) to gauge. No damage to the original wiring and works great.

[porschetub]

That dash volt meter is great for reminding you the blinker is on, and that's all. I put a relay in and wired mine direct to the battery. Now it is useful. The original wiring to the meter now turns on the relay which brings fused 12v direct (more like 13.7 when the car is running) to gauge. No damage to the original wiring and works great.

I found too much signal loss and my voltmeter wouldn't read any more than 12v powered off old centre console wiring,changed the supply to my Hella aux fuse board with direct feed to battery and achieved the correct reading as per battery .
Cheers.

[SKL1]

Good to know. Thx guys.

[barefoot]

I substituted the cigar lighter for a USB double port with built in voltmeter, so it gets its power from that circuit. Typically reads 13.4 V

[930cabman]

I substituted the cigar lighter for a USB double port with built in voltmeter, so it gets its power from that circuit. Typically reads 13.4 V

or a cheapie "battery checker" plugged into the cigar lighter.

OP: have you confirmed voltage with a VOM?

[GregAmy]

You should check the battery voltage with a DMM.

+1. That console voltmeter is not consistently accurate (sometimes never). Mine used to flicker with the brake and turn signals and one time (before I replaced the fuse panel with the JWest one) I jostled the fuse loose with my knee while well away from home and it gave me a scare.

That, along with desire for more knee room, was one of the driving factors for my removing the console gauges entirely.

What matters is the voltage at the battery. Check it there.

[SKL1]

My initial entry was a little simplified- I actually swapped engines in my '73 2.0. With the original engine the voltmeter in the console (OEM) would read under 12V at first when driving and would then, after a few miles, read over 12 or 13.

I put the modified engine from my '71 in the 2.0 and since then the voltmeter never even gets to 12V no matter how far I drive. That is why I wondered if the alternator wasn't working as well as the one in the 2.0 engine.

Does this make sense?? (IMG:style_emoticons/default/smile.gif)

[emerygt350]

Yes, but you really shouldn't even look at that voltmeter unless you run it directly to battery. Get a DMM on the posts while the car is running.

[GregAmy]

I put the modified engine from my '71 in the 2.0 and since then the voltmeter never even gets to 12V no matter how far I drive.

And yet the battery is never flat, engine never fails to crank at start and never loses juice? Then it's charging correctly.

Volt Ohm Meter (VOM/DMM) on the battery. Expect ~12.5 volts at rest with key on, ~13.5V while running.

Curious: same or different alternator?

[SKL1]

Both engines have their original alternators which have never been fiddled with. Swapped entire engines with their original alternators.

I'll take measurements directly from the battery and see what I find...

[Spoke]

On my car I measured the battery voltage and recorded the voltage on the center console voltmeter after starting and at higher RPM with headlights off and all exterior marker lights on. The voltage on both did not change with RPM.

The battery was at 13.8V while the voltmeter was 13.0V. I checked the voltmeter before installing a while back and it was within 0.1V from 9V to 16V so the voltmeter is quite accurate. Its placement in the wire harness accounts for the difference in voltage.