Voltage Mystery

[twistedtree]

People are making this much more complicated than it needs to be. Check the voltage at the meter terminals with a known good meter. If the two don't agree, the meter is defective and should be replaced.

Yes, please just do this. It's so easy and will tell you so much.

 

[Roger Long]

Yes, please just do this. It's so easy and will tell you so much.

I will and already would have done so on my last boat with it's hinged electric panel that I could just tip out (carefully because of the live AC).

However, the Gulf Star one has to be unscrewed and everything is quite difficult to get at.

This is a recently purchased boat. Although 1975, it is in remarkably good structural and cosmetic condition. I haven't found a water stain or leak yet. However, I've been taking care of lots of system things while in delivery mode. Leaving this morning headed for FL just ahead of the marina closing.

I'll report when I finally get the panel apart. BTW, one of those little 3 LED testers in the outlets show everything copacetic.

 

[BobH]

We had one of those panels that had to be unscrewed to get behind it. Built a frame for it and hinged the frame and never looked back.

 

[rwidman]

............ would have done so on my last boat with it's hinged electric panel that I could just tip out (carefully because of the live AC)...............

Or, you could unplug the shorepower cord first.

 

[oscar]

Or, you could unplug the shorepower cord first.

That's cheating.

 

[Skipper_Vic]

If your still looking for help re your ac volt meter reading 1/2 of its terminal voltage; here is my thoughts.
Your AC volt meter likely contains a bridge rectifier (four diodes that "full wave rectify" the incoming ac to pulsing DC). If one "half" of this rectifier has gone bad (open), your meter will only "see" 50% of the dc pulses and therefore only read exactly half voltage.

You can test this by disconnecting all AC wires and then touching 12 VDC (or 24 VDC) from your boat's batteries to the meter's terminals. Swap the "polarity" and test again. If your meter only reads in one "polarity", you have a bad bridge rectifier.

If this is the case, there is a work-around. Purchase a bridge rectifier (2 amp. / 250 volt rating or so is fine). Connect the two "AC Line" wires to the "AC Input" of the bridge rectifier and connect the meter to the bridge rectifiers "DC Output". You might need to swap the polarity once at the DC meter terminals to get it to read.

It might be more messing about than its worth but it is my MacGyver fix FWIW. It should work. Vic

 

[Roger Long]

It might be more messing about than its worth but it is my MacGyver fix FWIW.

Thanks. That would be a lot easier than trying to get the whole meter out of it's tight location.

For the time being, my MacGyver fix is to just multiply by two in my head.

 

[rwidman]

If your still looking for help re your ac volt meter reading 1/2 of its terminal voltage; here is my thoughts.
Your AC volt meter likely contains a bridge rectifier (four diodes that "full wave rectify" the incoming ac to pulsing DC). If one "half" of this rectifier has gone bad (open), your meter will only "see" 50% of the dc pulses and therefore only read exactly half voltage.

Yes, this is a possible failure mode. Your suggestion on how to deal with this is theoretically correct but in the real world, we would just say the meter is bad and replace it.

Unless the meter is something that cannot be replaced, it's far simpler to buy a replacement and install it. If the meter is "special" and no replacement can be found, it could be sent to a shop for repair. This repair is something that's past the average boater's ability to deal with.