Voltmeter reading? Accuracy? Options

[SKL1]

Trying to figure out how accurate the OEM voltmeter is in my '73 2.0. To make a long story shorter the engine in the car is a much modified 1.9 from my '71, with approx 120K miles on the alternator.

Voltmeter reads around 11V and drops to 10 if I turn on the headlights. Immediately goes back to 11 or just over that with the lights turned off.

Replaced the voltage regulator this AM and did a test drive with no change. Gauge never gets close or above 12V. Makes me afraid to drive it at night with the lights on and go very far.

Do I need to go through the hassle of rebuilding the alternator or trying the alternator from the original 2.0 engine that has about 70K miles on it?

Better way to get a more accurate reading of actual voltage?? I hate electrical issues!!!!

TIA.

[mjrrti]

Trying to figure out how accurate the OEM voltmeter is in my '73 2.0. To make a long story shorter the engine in the car is a much modified 1.9 from my '71, with approx 120K miles on the alternator.

Voltmeter reads around 11V and drops to 10 if I turn on the headlights. Immediately goes back to 11 or just over that with the lights turned off.

Replaced the voltage regulator this AM and did a test drive with no change. Gauge never gets close or above 12V. Makes me afraid to drive it at night with the lights on and go very far.

Do I need to go through the hassle of rebuilding the alternator or trying the alternator from the original 2.0 engine that has about 70K miles on it?

Better way to get a more accurate reading of actual voltage?? I hate electrical issues!!!!

TIA.

I just bought a cig lighter usb charger on Amazon for about 9 bucks. It has a digital volt meter built into it. I bought it for usb use but it reads the same as the aftermarket sun pro voltmeter I have in my car. Should give you a good idea of where your factory gauge stands. I don’t know how to attach a link but here is a pic.

[mjrrti]

The brand didn’t show in my pic but it is zeehoo. There are a bunch to choose from anyway. (IMG:style_emoticons/default/smile.gif)

[930cabman]

I have found voltmeter readings somewhat erratic, but mine does read 14V often and has never let me down. But I also have one of the cigar lighter "meters"

[emerygt350]

It's really not the voltmeter, I checked mine against a nice multimeter and it shows pretty dead on to that. The problem is where it is tapped into the system. Unless you run a direct wire from the volt meter to the battery you really only have another method of knowing your brake light is working.

I put a relay inline using the original wiring of the volt meter to trigger it. I have fused wire running from the relay to the battery and to the relay -> volt meter. The volt meter is now key activated (using the original wiring) and it only tells me what the battery is seeing. I went from a situation you describe to a nice steady 13.8.

I also use a digital adjustable voltage regulator and highly recommend them. Cheap, sturdy, and fits the slot.

[GregAmy]

Trying to figure out how accurate the OEM voltmeter is in my '73 2.0.

It's not. Measure the voltage at the battery while the engine is running.

My voltmeter gave me enough scares - usually while well away from home - that I just removed the whole center console to give my 6'1" frame a bit more legroom. The idiot lights and fuel gauge-installed oil temp keep me honest.

I did add some extra LEDs to catch my attention, though. - GA

[SKL1]

Thanks. The meter in the lighter sounds great but I took the lighter out some 40 years ago and replaced it with an oil temp gauge.

I'll measure at the battery and see what gives...

[SKL1]

Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6.

Not sure what the h*ll that means but obviously the OEM meter is kind of useless...

Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif)

[Superhawk996]

1) Means your battery isn’t charging.
2) Means you’re getting a significant voltage drop across wiring between the battery and the voltmeter.

[emerygt350]

It means either the alternator is shot or your voltage regulator is shot. The vr is 35 dollars so start there. If that doesn't fix it then the alternator. Not terrible to replace or pay for. That difference between the battery and the gauge is what you get unless you alter the voltmeter wiring.

[GregAmy]

Yup, charging system inop.

Is you GEN light on? You haven't replaced that bulb with an LED, have you?

OP said he replaced the voltage regulator so now it's time for some additional troubleshooting.

http://www.914world.com/bbs2/index.php?s=&...t&p=2600844

https://www.pelicanparts.com/techarticles/9...mments_Bookmark

[Spoke]

Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6.

Not sure what the h*ll that means but obviously the OEM meter is kind of useless...

Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif)

@SKL1

As others mentioned, it seems your alternator/VR is not functioning.

A couple of tests:

1) Is the GEN light on before cranking the engine? If the GEN light is not on then either the GEN light is burned out, or fuse blown, or an issue with the VR or alternator.

2) Once running, at the alternator connector on the relay board, measure (Don't disconnect anything):
- D+ to chassis; should be 14V
- DF to chassis; should be 5-9V
- D- to chassis; should be 0.0V

[930cabman]

Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6.

Not sure what the h*ll that means but obviously the OEM meter is kind of useless...

Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif)

@SKL1

As others mentioned, it seems your alternator/VR is not functioning.

A couple of tests:

1) Is the GEN light on before cranking the engine? If the GEN light is not on then either the GEN light is burned out, or fuse blown, or an issue with the VR or alternator.

2) Once running, at the alternator connector on the relay board, measure (Don't disconnect anything):
- D+ to chassis; should be 14V
- DF to chassis; should be 5-9V
- D- to chassis; should be 0.0V

Great information Spoke, thanks

how is your 930 build coming along?

[Spoke]

how is your 930 build coming along?

Coming along slowly which I'm ok with. Mark has the long block and transmission done. Was accumulating parts for the build the last I spoke with him.

I'm getting the chassis ready:
- refurbished drive shafts
- New wheel bearings in driver rear; passenger rear bearings done about 10 years ago.
- New clutch cable
- New front wheel bearings
- PMB restored calipers
- New rubber gaskets in the engine compartment

Looking to have the car back together by spring.

[porschetub]

Measured voltage at the battery with a multimeter- had 11.71 just sitting there with the engine off. At idle it still said about 11.7, with the OEM voltmeter reading between 10 and 11. Revving it didn't do much. Turned on the headlights and the OEM meter went down to 10, with the meter at the battery reading about 11.6.

Not sure what the h*ll that means but obviously the OEM meter is kind of useless...

Any electrical genius tell me what that means? (IMG:style_emoticons/default/smile.gif)

(IMG:style_emoticons/default/agree.gif) with the comments about no charge and the voltage @ the gauge ,when I fitted my new dash mounted voltmeter i wired to the centre console wiring which I found in good condition ,the voltage was the best part of 1volt lower than the battery which was new as the VR ,alternator was fully rebuilt very recently.
I had previous installed a secondary Hella fuse box under the dash with a heavy duty fused supply to the battery ,jumped off that and the gauge was correct to voltage @ battery by 0.1 of a volt ,so happy with that and will stay like that ,cheers

[VaccaRabite]

One of these days I need to run a wire back to the battery for the volt meter.
My car had a long history of electrical gremlins, which I have resolved over the years. But the volt meter is a cause for stress as it currently gets hit by load when the lights and wipers are working, and does not give an accurate view of what's actually happening at the battery.

Zach

[emerygt350]

One of these days I need to run a wire back to the battery for the volt meter.
My car had a long history of electrical gremlins, which I have resolved over the years. But the volt meter is a cause for stress as it currently gets hit by load when the lights and wipers are working, and does not give an accurate view of what's actually happening at the battery.

Zach

Definitely worth the time and effort.

[chmillman]

So while we’re on this discussion here, this has also been something I have wanted to do… How do you route the wire from the battery to the passenger compartment? I was thinking down under the tin and then through the tunnel, but there isn’t an opening available I can see to thread the wire through… thought about maybe making one somewhere near where all the various cables (clutch, parking brake, speedo) come out.

[FlacaProductions]

I've used the speedo cable hole for additional wiring.

[SKL1]

thanks for the extra replies guys- I've got some work to do as I would like to use my headlights every so often and not worry about getting home!!