Aftermarket Voltmeter

[gnick]

Hi Guys,

I did a search on this but wasn't able to find much. The P.O. of my M1009 put in an aftermarket voltmeter (see attached photo). Everytime I plug it in it pops the 28v fuze. I hooked it directly up to 12v and it pins the meter as well, so I'm sure its set up for 12v not the 24v charging system. I'd rather just buy one that makes sense vs. trying to rig up resistors onto it, unless I can get an original. Have any of you guys found an aftermarket voltmeter that will work? I'm looking for an original replacement as well if anyone has one.

thanks for the help.

 

[cpf240]

That is an amp meter, not a volt meter, so I'm not surprised it is blowing the fuse, as it appears as a short circuit.

 

[gnick]

right - i was really confused by that as well.

 

[cpf240]

Amp meters measure the flow of current, like how much a fan motor is drawing, etc, and thus must be in-line with the thing being measured. Putting one in place of the stock voltmeter, without changing the way it is wired, will create a dead short.

Using an off-the shelf 12v volt meter should not be a problem, just put the correct amount of resistors between the connections on the back of the meter. If I recall correctly, the stock meter used a 300 ohm resistor for this.

 

[gnick]

makes a lot of sense, and now i feel like an idiot for not remembering they measure different things. haha. thanks for help

 

[gnick]

bought this one that i found in another thread. Pricy, but it should be a good replacement that reads the correct voltage.

http://www.issprogauges.com/Classic-20-32-Volt-DC-Voltmeter-Gauge-p/iss-r8661.htm

 

[cpf240]

That should do it!

One thing to remember... the 24v wire to the gauge is hot at all times, and it is easy to short it out on the dash, etc. The ground for the gauge is provided by one of the relays under the dash next to the GEN 2 relay and the starter relay. So, the gauge must be isolated from being grounded through its housing, or it will be 'on' all the time. This is accomplished by the metal bracket being attached to the plastic instrument cluster trim. This also means that the light bulb for the gauge needs two wires instead of just one. Though I suppose it could get its ground via the gauge housing when the voltmeter relay is engaged...

 

[gnick]

If anyone was interested, I put that ISSPRO gauge in last night and did the Doghead mod. It's plug and play. Although the original voltmeter light only has 1 wire running to it so I'll have to find another way to light the gauge up. Anyways, here is the video. Seems to be working correctly. Although I wasn't expecting it to read anything when the ignition is off, but it does.

Happy to see my Gen2 light is working now as well. I was worried I would need to dig into that too.

https://www.youtube.com/watch?v=mWrRVSGsl5U&feature=youtu.be

 

[cpf240]

If it is actually reading, not just staying where it was when turned off, then it is getting a ground from somewhere. This could, over a long period of sitting, drain the batteries a bit. As to the light, I had thought the original one had two wires, but as it only had one, it was using the gauge housing for its ground. You should be able to do the same. Try connecting one of the bulb wires to one of the gauge mounting studs, which *should* be grounded when the voltmeter relay is engaged under normal conditions, and connect the other wire to the original voltmeter light wire.

 

[cucvrus]

cpf240 has the answer. It is getting a ground. You must isolate the voltmeter from the ground. Use a barrier of some sort tape plastic. You must keep the ground from getting to the gauge when the key is shut off. I have done this and am at a loss for words to write about what exactly I did to get that resolved. I do know it was easy. Check it out and let us know. Good Luck.

 

[gnick]

thanks guys

ill give that a shot