Voltmeter - mapping voltages to markings

[HelluvaEngineer]

Hi everyone. My voltmeter died shortly after buying my m1009. Thanks for all who contributed helpful posts that came up on my search regarding debugging the voltmeter. I checked at the connections and I was getting 24v. So I pulled it. Then I took it to my shop and connected the 12v lug to my voltage supply. I came back to life. So it's safe to assume the resistor died. Looking at it closely it appears there should be copper contact points on the ends and they're no longer there.

I didn't have any 300 ohm resistors but I did have a pack of 150's. So I soldered two in series and gave it 24v. Now it's working great.

Since it was already connected to a variable voltage supply I ran a test to see the voltage required to hit each line on the meter. I also did a 24.0v test. I think the meter is pretty accurate! Anyway, maybe this will be helpful to someone in the future who's trying to debug their meter.

15.1v = Start of red (or some faded red-ish color)
18.9v = Start of yellow
22.2v = Start of green
24.0v = Middle of green
26.7v = Start of orange-ish color
32.1v = End of orange-ish color

 

[HelluvaEngineer]

I should have mentioned - I checked the impedance across my makeshift resistor pack and it was 297-298ohm, so definitely within 1% tolerance. It was also interesting that the next time I started the truck the meter slowly went up into the middle of the end range. So maybe 29 or so volts coming out of the alternators. Normal or is that cooking my batteries?

 

[Tinstar]

Install a 24v VM and never look back.
No resistors, no soldering, no mapping voltages.

Why GM did it that way is beyond me.

 

[n8roro]

My VM is not working currently, and taking of the dash will happen one of these days. Let me see if I understand this correctly. The stock VM has a resistor that can fail and either the resistor can be replaced or just upgrade to a 24v VM. Is that right?

 

[MarcusOReallyus]

That's correct.

 

[HelluvaEngineer]

My VM is not working currently, and taking of the dash will happen one of these days. Let me see if I understand this correctly. The stock VM has a resistor that can fail and either the resistor can be replaced or just upgrade to a 24v VM. Is that right?

Yes. And the worst part is the resistor is pink. On mine anyway.

Sent from my VIVO XL using Tapatalk

 

[Tinstar]

You can use a standard military one or VDO and ISSPRO make excellent 24v voltmeters.

 

[HelluvaEngineer]

You can use a standard military one or VDO and ISSPRO make excellent 24v voltmeters.

I know you guys will hate me but I found an overseas source for 30v digital voltmeters for about $3 each. I'm going to put one next to the analog one on that panel. Plus a switch likely...for something.

Sent from my VIVO XL using Tapatalk

 

[Bighorn]

I know you guys will hate me but I found an overseas source for 30v digital voltmeters for about $3 each. I'm going to put one next to the analog one on that panel. Plus a switch likely...for something.

Sent from my VIVO XL using Tapatalk

It's your truck but.. why 2 voltmeters?
I put an oil pressure gauge next to my voltmeter so I am no purist.
Just curious.

 

[HelluvaEngineer]

It's your truck but.. why 2 voltmeters?
I put an oil pressure gauge next to my voltmeter so I am no purist.
Just curious.

Oh. Just to get an accurate reading. I could get a VDO gauge but just being a cheapskate.

Sent from my VIVO XL using Tapatalk

 

[Bighorn]

Oh. Just to get an accurate reading. I could get a VDO gauge but just being a cheapskate.

Sent from my VIVO XL using Tapatalk

I am that way too but about oil pressure and temperature.
My M1009 has the 24 volt meter without the resistor and it reads 2 volts high according to my Fluke multimeter.
Now see what you did?!
Now it is gonna bother me that my voltmeter is off!
Oh ebay...

 

[HelluvaEngineer]

I am that way too but about oil pressure and temperature.
My M1009 has the 24 volt meter without the resistor and it reads 2 volts high according to my Fluke multimeter.
Now see what you did?!
Now it is gonna bother me that my voltmeter is off!
Oh ebay...

What will drive you nuts is a mechanical oil pressure gauge. I have one on my Z28. You can watch the pressure bleed off your bearings when you lay on it. That said it makes over 100 psi on cold start. Figure 10 psi per 1000 rpm when warm is sufficient.

Sent from my VIVO XL using Tapatalk

 

[Tinstar]

I have an ISSPRO 24v voltmeter and my Fluke DMM says it’s spot on.
Don't skimp on gauges. The VMs aren’t that expensive anyway.
They are the eyes on the health of the truck.

 

[Bighorn]

Why not?
I already invested 2 grand in repairs and upgrades into my M1009, might as well get a voltmeter that reads accurate.
Yea, the mechanical oil pressure gauge is fun.
The difference between cold and hot oil bleed off after shut down is astonishing.

I still find it odd the Cucv's have idiot lights for temp and oil pressure but no gauges while having gen lights AND a voltmeter.
Would it have killed them to but a temp and oil gauge in? Even the crappy electrical ones GM used.
When I got this M1009 I bought it at the Portland airport and drove it back to Wyoming.
It drove great except the lack of proper gauges made me feel like I was blindfolded the whole way.
I even bought the gauges I have installed now along the way back, on the second day driving it home.
I used a tee to keep the stock idiot light for oil pressure operative along with my mechanical gauge.
Just in case I am spacing out on the temp gauge.. the idiot light for oil pressure can grab my attention to fret over the oil gauge.
Okay.
I just answered my own question on why no gauges in the cucv stock.

 

[TechnoWeenie]

Amazon has a dual voltage meter..... Less than $20.. I have one, need to install it.

Per SS policy, NOT an auction...

https://www.amazon.com/gp/product/B0721PQCKD

Easy to monitor each batt, front 12V and rear 24V combined.

 

[Tinstar]

Why not?
I already invested 2 grand in repairs and upgrades into my M1009, might as well get a voltmeter that reads accurate.
Yea, the mechanical oil pressure gauge is fun.
The difference between cold and hot oil bleed off after shut down is astonishing.
I still find it odd the Cucv's have idiot lights for temp and oil pressure but no gauges while having gen lights AND a voltmeter.
Would it have killed them to but a temp and oil gauge in? Even the crappy electrical ones GM used.
When I got this M1009 I bought it at the Portland airport and drove it back to Wyoming.
It drove great except the lack of proper gauges made me feel like I was blindfolded the whole way.
I even bought the gauges I have installed now along the way back, on the second day driving it home.
I used a tee to keep the stock idiot light for oil pressure operative along with my mechanical gauge.
Just in case I am spacing out on the temp gauge.. the idiot light for oil pressure can grab my attention to fret over the oil gauge.Okay.
I just answered my own question on why no gauges in the cucv stock.

One of the first things I did when first getting truck is install gauges.
Oil pressure , Water temp, Trans temp.
The VM was missing so installed a 24v one.
Last and best one was RPM.

Took some time as I researched it quite a bit.
Bought the VDO model and it reads the signal from GEN1 and works great!!

Would drive me nuts not knowing what the engine was doing.

2K in repairs and upgrades?
That’s about right to get a CUCV to a decent level of reliability.
Amazing how the little things add up.

 

[Bighorn]

One of the first things I did when first getting truck is install gauges.
Oil pressure , Water temp, Trans temp.
The VM was missing so installed a 24v one.
Last and best one was RPM.

Took some time as I researched it quite a bit.
Bought the VDO model and it reads the signal from GEN1 and works great!!

Would drive me nuts not knowing what the engine was doing.

2K in repairs and upgrades?
That’s about right to get a CUCV to a decent level of reliability.
Amazing how the little things add up.

OOO.. RPM gauge.
You know, this website is tough on my wallet.

Well I did the following because I like wrenching and I am never "that guy" stuck on the side of the road.. I am the guy with the tools helping "that guy".
Replaced broken front hubs on ride home after purchase.
Changed all fluids/filter upon arrival home
Replaced water pump
Replaced Harmonic balancer with Fluidampr model.
Replaced Injection pump with rebuilt model from Oregon Fuel Injection.
Replaced transmission vacuum signal transducer (on ip pump)
Installed Paradox cooling system upgrade
Swapped the 10 bolt axles for a Dana 44 front 12 Bolt rear and 33 inch BFG KM2's I had on my other Blazer.
Replaced rear driveshaft u-joints.
Replaced radiator.
Replaced radiator hoses.
Installed a new set of AC Delco 60G glow plugs.
Installed Oil, water temp and pressure gauges.
Installed underhood worklight and additional backup light/flat tire fixin' light wired to the blackout light switch.
Replaced dash light bulbs and cleaned all ground wires on truck.

I have owned the truck a couple of months now.
You might say I am a little pro-active about maintenance.
There ain't a tow truck that comes up here when the snow is on the ground and besides; where would I tow my truck to? Me?
Much rather spend the money now and find all the problems I can than be stranded at minus 20 on a road nobody travels much in winter.

Left to do;
Install Phillips Zero Start propane coolant block heater (at the post office in town and can't get down till the hunters leave)
Replace injectors (Have socket and full set of brand new injectors)

But at this point, the M1009 is as reliable as my rusty 76 K5 which I drove to California to visit my Dad in last spring.
Note to future self; Never drive a 400 cu in Chevrolet small block powered brick 1,200 miles again.
Ran great, 9 mpg.. but ran great.
At least the M1009 still gets 18 mpg after the 3.73 swap.

I guess if I had a wife or a Ford vehicle, I would be spending even more money than that.

 

[MarcusOReallyus]

Amazon has a dual voltage meter..... Less than $20.. I have one, need to install it.

Per SS policy, NOT an auction...

https://www.amazon.com/gp/product/B0721PQCKD

Easy to monitor each batt, front 12V and rear 24V combined.

That's nice!

Another option is to get a couple of these small digital meters and mount them next to the existing meter, one for the front, one for the back.

 

[Bighorn]

I snapped up a New, in the box, DATCON made in U.S.A. 24 volt voltmeter.
Heavy duty series 831.
ebay again.
$20.95 plus $4.75 shipping.

The orbit of the Earth is corrected with this purchase and subsequent replacement of my inaccurate voltmeter.
Probably add another 40 horsepower to my 6.2.

 

[Tinstar]

That will work