What Am I Doing Wrong?

[StingrayL82]

When I had our Sovereign restored, the company who did the work pulled out the Univolt and put in an Iota converter. The plus side is it's quiet, the down side is that I lost the ammeter feature.

I finally got around to buying a Univolt on Ebay, and I took the fuse panel out and cannibalized the brass panel, where the ammeter leads connect to. Following the best electrical diagrams I have (pictures of other Univolts), I hooked up the panel.....nada, the ammeter doesn't even wiggle. I'm stumped, because I don't see how the setup would work anyway, given that both ammeter leads come from negative cables....battery gnd and load gnd.

Can someone shed some light on what I've done wrong? I'm attaching a picture of my Frankenstein setup. The black lead is attached to the trailer gnd and the white lead is attached to load gnd.....I think.

Thanks in advance for the responses.

[azflycaster]

The one lead needs to go to your battery and the other to the negative load so that the current can be measures going through this device. The diagram for mine is below.

BTW, mine does not work either...

[Xbob2]

Actually the amp meter is wired in series with the load being measured. But you notice the wires to the meter are so dinky they couldn't carry the load. In this situation the ammeter is connected to a shunt. the major portion of the current flows thru the shunt with a small portion being diverted to the meter to show measurement. You need to scab the shunt from the old unit and wire it in series with the load you want to measure. Also be sure that you have the shunt and not just a connecting block ... otherwise fried ammeter & wiring and maybe a fire!
Bob

Originally Posted by azflycaster

The one lead needs to go to your battery and the other to the negative load so that the current can be measures going through this device. The diagram for mine is below.

BTW, mine does not work either...

[StingrayL82]

Crap.

Richard and Bob, thanks for the help.

I hate messing with the electrical...last time I fried the ammeter and had to have it rebuilt by NyCo.

[Xbob2]

The shunt is a beefy hunk of metal with 4 connections ... the 2 little ones are the meter and the big ones are for the main power flow. Remember its wired in series with the hot side, not parallel! Also the ammeter and shunt have to be matched for accuracy. Thats why you have to scab an old unit.
Bob

Originally Posted by StingrayL82

Crap.

Richard and Bob, thanks for the help.

I hate messing with the electrical...last time I fried the ammeter and had to have it rebuilt by NyCo.

[StingrayL82]

Okay, Bob and Richard, talk to me as if I were the biggest retard on the planet who was capable of burning down the trailer. Here are two pics of the whole Univolt fuse board, one of the front and one of the back...I re-added the ammeter brass panel to the board.

Question #1: That black wire on the back of the board...where does it go? I'm almost 100% sure that the fuse block it goes to is the "Power Indicator On"...the one with the blob of solder.

I feel so dumb about this, but I want everything to work right.

on edit: This UniVolt, btw, came out of a 1970...don't know if that makes a difference, since ours is a 1971.

[Xbob2]

Originally Posted by StingrayL82

Okay, Bob and Richard, talk to me as if I were the biggest retard on the planet who was capable of burning down the trailer. Here are two pics of the whole Univolt fuse board, one of the front and one of the back...I re-added the ammeter brass panel to the board.

Question #1: That black wire on the back of the board...where does it go? I'm almost 100% sure that the fuse block it goes to is the "Power Indicator On"...the one with the blob of solder.
OK .. first I must explain that I am a total RV noob, (Give me a year ...)That said I know power systems from 3 phase 440 to kit electronic boards (think "Make Magazine") ac and dc.
the black wire comes from an off/on switch. The fuse protects the off/on indicator light.

I feel so dumb about this, but I want everything to work right.
K ...

on edit: This UniVolt, btw, came out of a 1970...don't know if that makes a difference, since ours is a 1971.

I doubt it but being a noob I don't know for sure.
Bob

P.S. I suspect the brass plate IS the shunt ... it would help if I knew what was being measured and the range of the meter.

[azflycaster]

There should be only three wires going to the back of the board. I have never pulled mine, but that is what the diagrams all show. There should be 2 heavy duty wires from the converter and a smaller wire for the power on light. The circuit for the power on light is only available on a Univolt converter. It is 12 volts and is isolated from the battery circuit or it would always be on. The connection on the front side of the board should run to where ever your power on light is located. On my 75 TW it is on the control center.

I do not have a Univolt converter in my trailer and because of that the power on light does not function.

[Xbob2]

Also per the your first picture ... you NEVER lug 2 wires under the same setscrew .... bad, bad, bad!

Originally Posted by StingrayL82

When I had our Sovereign restored, the company who did the work pulled out the Univolt and put in an Iota converter. The plus side is it's quiet, the down side is that I lost the ammeter feature.

I finally got around to buying a Univolt on Ebay, and I took the fuse panel out and cannibalized the brass panel, where the ammeter leads connect to. Following the best electrical diagrams I have (pictures of other Univolts), I hooked up the panel.....nada, the ammeter doesn't even wiggle. I'm stumped, because I don't see how the setup would work anyway, given that both ammeter leads come from negative cables....battery gnd and load gnd.

Can someone shed some light on what I've done wrong? I'm attaching a picture of my Frankenstein setup. The black lead is attached to the trailer gnd and the white lead is attached to load gnd.....I think.

Thanks in advance for the responses.

[StingrayL82]

Well, like I said, I'm capable of burning down the trailer, but I'm learning...my father was the Westinghouse engineer genius, but he never taught me any of this stuff.

I took two more pictures, and Richard what you wrote correlates to the pic and arrows. My question is, are those heavy duty wires hot? How can you have a hot wire on one side of the panel and the trailer gnd load on the other side, both attached to the same bolt?

If those two wires on the Univolt are hot, what do I use as a hot source now, since the Univolt was replaced with an Iota? I don't mind replacing the new fuse panel with the old Univolt panel...but the Power On ground wire in the back, where can I ground it to? FWIW, My Power On light at the Central Control Panel works.

Here are the pics. Thanks again guys for the replies and the patience.

[StingrayL82]

Bump.

If anyone can chime in on this subject, I'd be eternally grateful.

[azflycaster]

One of the two wires that connect on the back is +12 volts. The other is the return (ground). The return (ground) wire would be the one attached to the ground load. The +12 volt wire would attach to a point that would tie it to the + side of the battery and all of the fuses.

Hope that helps...

[Xbob2]

Excuse me but you are mistaken. Though I am an RV noob the old 12v fuse panel in these pictures has NO ground or 12 v negative connections on it. The top bolt is the 12v + distribution from the battery or power supply. The black wire comes from a pole of a power on/off switch. the bottom left and center bolts are the in and out of the ammeter shunt.
By contrast, the first picture in the thread of the new fuse panel there is a 12v dc - buss on the right side of the panel.
In the picture of the transformer you are looking at a power supply. 120 AC goes into the transformer and 12v ac comes out of it, is connected to the diodes on the heat sink. (The round thingies) The diodes are half of a rectifier circuit. Thats something that changes AC to DC. The other half of the circuit that isn't shown in the picture is a pair of capacitors. This can be used to charge a battery or power 12v equipment or both.
After all that, that doesn't help you get your ammeter working. You were half right in your wiring ... the ammeter gauge connects to the small terminals of the shunt but you might of had the wires reversed.
The large bolts "interrupt" the hot wire of circuit you want to measure.
The range of your gauge tells you how many amps your shunt can take.
This is where my lack of RV systems knowledge fails you ... I don't have clue where you put the shunt!
Can someone else step up?
Bob

Originally Posted by StingrayL82

Bump.

If anyone can chime in on this subject, I'd be eternally grateful.

Originally Posted by azflycaster

One of the two wires that connect on the back is +12 volts. The other is the return (ground). The return (ground) wire would be the one attached to the ground load. The +12 volt wire would attach to a point that would tie it to the + side of the battery and all of the fuses.

Hope that helps...

[StingrayL82]

Okay, Bob, I'm tracking what you and Richard are saying. The only thing I can add to this mystery is that there are no capacitors (as I recognize them) on this Univolt. I have two Univolts, one from 1970 and the other from a later model, possibly 1980's....the newer Univolt has three recognizable capacitors....the 1970's Univolt has a 2"x3" circuit board, and the solder is crystalized.

So, as I understand it, my updated pics should be correct, with the exception of what attaches to the back of the shunt...I know that, when the panel was attached to the Univolt, the solid metal wire attached to the back of the shunt, completing the circuit and allowing the ammeter gauge to read amperage....so the million dollar question now is, what attaches in place of the transformer solid metal wire in the back of the shunt?

on edit: Feel free to save the pics, black out what I wrote, and correct my mistakes. That brass shunt, by the way, is completely separate and independent of the fuse portion of the panel. It is in no way attached to the fuses.

[meadowlm]

Based on the schematic that Azflycaster put up, the shunt has four connections.
1 to the battery neg through a fuse
2 to the neg load
3 and 4 to the ammeter.

The top picture shows the shunt 1 and 2 both connected to the ground bar which will bypass the shunt. Remove the big wire going to the neg side of the battery from the ground bar and run it straight from the shunt (to a fuse) then to the battery.

Also make sure the shunt is insulated (do not mount it to anything conductive).

Will

[Xbob2]

Stingray, First off you need to do some due diligence ... Google capacitor and look at some of the pictures. They come in all shapes and sizes. But the discussion of capacitors is irrelevant to getting your ammeter working.
You also need to Google series and parallel circuits ... so you can see pictures and understand the terminology. Your Mag light is an example. You pop in 2 AAs ... the + of one battery contacts the - of the other. The 2 batteries are in series. My Dodge turbodiesel has 2 honking 12 volt batteries in the engine bay ... the + of one is connect to the + of the other and - of both go to chassis ground. This is parallel. Other examples of series and parallel in an Airstream is the fuse is in series to protect the circuit ... the tail lights and clearance lights are in parallel on one circuit.
I don't know how to do pictures yet so can't help you there.
If I could see a diagram I could tell you where to put the shunt.
Give me 2 months and I will be able to tell you all about rv power but now I am days away from picking up my first trailer, and this is all I can do with the info at hand.

Originally Posted by StingrayL82

Okay, Bob, I'm tracking what you and Richard are saying. The only thing I can add to this mystery is that there are no capacitors (as I recognize them) on this Univolt. I have two Univolts, one from 1970 and the other from a later model, possibly 1980's....the newer Univolt has three recognizable capacitors....the 1970's Univolt has a 2"x3" circuit board, and the solder is crystalized.

So, as I understand it, my updated pics should be correct, with the exception of what attaches to the back of the shunt...I know that, when the panel was attached to the Univolt, the solid metal wire attached to the back of the shunt, completing the circuit and allowing the ammeter gauge to read amperage....so the million dollar question now is, what attaches in place of the transformer solid metal wire in the back of the shunt?

on edit: Feel free to save the pics, black out what I wrote, and correct my mistakes. That brass shunt, by the way, is completely separate and independent of the fuse portion of the panel. It is in no way attached to the fuses.

[Xbob2]

Ignore this!!! I don't know what I'm talking about!!!

Originally Posted by Xbob2

Excuse me but you are mistaken. Though I am an RV noob the old 12v fuse panel in these pictures has NO ground or 12 v negative connections on it. The top bolt is the 12v + distribution from the battery or power supply. The black wire comes from a pole of a power on/off switch. the bottom left and center bolts are the in and out of the ammeter shunt.
By contrast, the first picture in the thread of the new fuse panel there is a 12v dc - buss on the right side of the panel.
In the picture of the transformer you are looking at a power supply. 120 AC goes into the transformer and 12v ac comes out of it, is connected to the diodes on the heat sink. (The round thingies) The diodes are half of a rectifier circuit. Thats something that changes AC to DC. The other half of the circuit that isn't shown in the picture is a pair of capacitors. This can be used to charge a battery or power 12v equipment or both.
After all that, that doesn't help you get your ammeter working. You were half right in your wiring ... the ammeter gauge connects to the small terminals of the shunt but you might of had the wires reversed.
The large bolts "interrupt" the hot wire of circuit you want to measure.
The range of your gauge tells you how many amps your shunt can take.
This is where my lack of RV systems knowledge fails you ... I don't have clue where you put the shunt!
Can someone else step up?
Bob

[Jim & Susan]

Originally Posted by meadowlm

Based on the schematic that Azflycaster put up, the shunt has four connections.
1 to the battery neg through a fuse
2 to the neg load
3 and 4 to the ammeter.

The top picture shows the shunt 1 and 2 both connected to the ground bar which will bypass the shunt. Remove the big wire going to the neg side of the battery from the ground bar and run it straight from the shunt (to a fuse) then to the battery.

Also make sure the shunt is insulated (do not mount it to anything conductive).

Will

Hey Will, now I'm really confused. The shunt appears to be connected directly between the lugs that feed the positive and negative battery cables on my '73 Univolt. See picture attached. Is that correct? Keep in mind I have no idea how an ammeter works, other than it measures draw on the battery (in this case).


Well, I can't get the picture to upload for some reason, I'll try that a little later.
Jim

[Jim & Susan]

Try again...

[StingrayL82]

I thought the ammeter was supposed to tell you how many amps you were hooked up to...


Crap....