Voltmeter Reading Question

[tgtaylor64]

I have two M1009s; on one, the factory voltmeter appears to always read battery voltage, even when the truck is off. It is in the yellow zone when off. On the other, when I turn the ignition off, the voltage drops to the far left (red zone), like it is not reading any voltage. Both trucks are stock. Why the different readings?

 

[skajm]

one could be wired wrong. when truck is off the voltmeter should turn off or it could drain the battery. may take a while to drain. disconnect the batteries and turn key on meter should read zero. connect battery and meter should read battery volage

 

[doghead]

Use a DMM and measure if there is voltage with the key off.

 

[cpf240]

Is there anything else mounted next to that voltmeter? The base-plate the voltmeter is mounted to needs to be isolated from ground, as that is how the gauge is wired, IE hot 24v at all times, with the ground connection switched by the relay under the dash when the key is on. Adding another gauge or something next to the voltmeter could be providing a ground path, causing the meter to be 'on' all the time.

 

[cucvrus]

You have an after market gauge that gets a ground thru the gauge case/housing. I had this in the past. You need to get the voltage/ ground isolated away from the gauge case. The case does not need to be grounded. The stock voltage meter light has it's own ground. I use a VDO332-902 gauge and have eliminated the grounding constant voltage reading with the use of this type of gauge. I hope that helps. Even if I could not express myself clearly. You get the jest of it. And this VDO 332-902 gauge has actual numbers on it.