Testing amp gauge while out of vehicle

[36humpback]

I have acquired a second amp gauge, and want to check it while not in the vehicle.  I am assuming that a wire from the generator to one stud, and a wire from the battery to the other stud.  Start engine and check at higher than idle speed.  Is that correct?  Would I have to ground the amp gauge somehow?  Thanks in advance.  Bob

Edited March 26 by 36humpback (see edit history)

[Bloo]

That should work.

 

35 minutes ago, 36humpback said:

I am assuming that a wire from the generator to one stud, and a wire from the battery to the other stud. 

Yes, so the current has to go THROUGH the ammeter.

 

35 minutes ago, 36humpback said:

Would I have to ground the amp gauge somehow?

No. Don't ground it. A good ammeter is a dead short internally. They run with both sides hot.

 

The battery being used for the test must have the other post grounded to the car as normal.

 

I am making the bold assumptions that 1) the car's charge wiring is disconnected from the generator (tape it, it's hot). and 2) the cutout/regulator box is still on the generator, as it would be in a mid 30s Dodge, and you are connected to the cutout/regulator where the car's wiring would normally connect. I don't know how many amps you will get, but it should sure show you which direction is which.

 

Regarding item 2 above, I think I remember from some other thread that you have a newer generator? If so, you'd best tell us what you have, because if there is an external regulator box on the firewall  you would have to turn the generator "on" by "full fielding" it. In that case a different hookup might be easier.

 

 

Edited March 26 by Bloo (see edit history)

[36humpback]

54 minutes ago, Bloo said:

That should work.

 

Yes, so the current has to go THROUGH the ammeter.

 

No. Don't ground it. A good ammeter is a dead short internally. They run with both sides hot.

 

The battery being used for the test must have the other post grounded to the car as normal.

 

I am making the bold assumptions that 1) the car's charge wiring is disconnected from the generator (tape it, it's hot). and 2) the cutout/regulator box is still on the generator, as it would be in a mid 30s Dodge, and you are connected to the cutout/regulator where the car's wiring would normally connect. I don't know how many amps you will get, but it should sure show you which direction is which.

 

Regarding item 2 above, I think I remember from some other thread that you have a newer generator? If so, you'd best tell us what you have, because if there is an external regulator box on the firewall  you would have to turn the generator "on" by "full fielding" it. In that case a different hookup might be easier.

 

 

I do have a newer 2 wire 35 amp generator, and a firewall mounted voltage regulator.  I had both tested (apart and together), and both work and are compatible.  So if I'm reading it right I unhook the gen wire and use wire from post to ammeter.  Wire from battery to other post and try it.  Should I unhook wires to ammeter still in the truck?  Thanks BLOO.

[Bloo]

Well, since you have an external regulator, I don't think it will turn on and start charging. That's why I asked. I would disconnect the wire at the BAT terminal on the regulator. Hook the wire you took away from the BAT terminal of the regulator to one post of the ammeter. Hook the other ammeter post to the BAT terminal. That should work.

 

 

[36humpback]

2 hours ago, Bloo said:

Well, since you have an external regulator, I don't think it will turn on and start charging. That's why I asked. I would disconnect the wire at the BAT terminal on the regulator. Hook the wire you took away from the BAT terminal of the regulator to one post of the ammeter. Hook the other ammeter post to the BAT terminal. That should work.

 

 

Thanks again.  I don't have to hook up a wire from the generator to the ammeter?

[Frank DuVal]

To check the ammeter I would just connect one wire to the hot battery terminal (whether + or - depending on if positive or negative ground) and the other terminal to the wire to a head lamp or heater motor. It should read. Read what? Well, that depends on the amp rating of the head lamp or heater motor. Or do you mean to test the charging system?

[Ben Bruce aka First Born]

Your goal is simply to see if the gauge works?     I would set a battery on my work bench.   Two  "jumpers, with alligator clips if available,  wire with bare ends if not.   ANYTHING to create a draw.  Motor, fan [motor],  head lamp, or other lamp with enough "draw" to read.   Connect a jumper to each battery post.  Connect either one to one post on the gauge.  Connect one jumper to the other post on the gauge, connect the other end of THIS jumper to the head lamp.  Connect the jumper from the other battery post to the other terminal on the Lamp [ motor],.   Gauge will show either a draw or charge,  Switch leads at the battery  to check for opposite reading.   I THINK.

 

 As old-tank says, check back.

 

  Ben

[Bloo]

You have to break the following circuit somewhere... The normal current path for charging is as follows:

 

Generator post >> "GEN" terminal [[regulator box]] "BAT terminal >> existing ammeter post [[ammeter in car]] other existing ammeter post >> post on starter >> battery cable >> battery post [[battery]] other battery post >> other battery cable >> body/frame/engine/straps/whatever >> generator bracket/case

 

Think if it as a big loop from the generator to the battery and back. If you want to measure current while charging, you have to break the circuit somewhere and insert your (second) ammeter. There shouldn't be any alternative path from the generator to the battery and back other than through your ammeter if you want useful results. I suggested at the "BAT" terminal of the firewall mounted regulator because it sounded like an easy place to break the circuit, but I haven't seen your truck. Anywhere in the loop would work.

 

Or to test the ammeter you could just do what @Frank DuVal and @Ben Bruce aka First Born said, and use a battery and a headlight. A 6v headlight draws about 8 or 9 amps or so at 6 volts. For example:

 

battery post >> ammeter terminal [[your ammeter]] other ammeter terminal >> headlight bulb terminal [[headlight bulb]] other headlight bulb terminal >> other battery post

 

Headlight should come on and ammeter should read about 9 amps charge (or 9 amps discharge, depending on which way the current is flowing through it).

 

Edited March 27 by Bloo (see edit history)

[dodge28]

If I read your question correctly all you want to know is if your ameter is working ? With the car running ( jumper wires in place on the  meter } hook one terminal to the battery post and the other terminal to the ground battery cable. That is putting the meter in serries. The meter will read one way or the other. 

[Ben Bruce aka First Born]

John, you said that a LOT neater than I!

 

  Ben

[36humpback]

Thanks to every one's help and advise.  I tried the jumper wires to a headlight bulb, and it worked.  Bulb came on and ammeter needle went to discharge side.   I will try the one in the dash now.  Hopefully I won't have to takeout  the meter that's already in, as I will have to take the whole cluster out.