Help wiring back of ammeter (I'm having trouble wiring up the back of the ammeter on my 36 Dodge panel)

[36humpback]

I'm having trouble wiring up the back of the ammeter on my 36 Dodge panel.  The wiring diagram is so grainy that I can't tell what wire goes where.  There are three studs on the back.  One above the the fuse and two below. the attached pic shows a stud next to fuse.  Is this the one above the fuse on my ammeter? With engine running the ammeter does not show charging, but when I turn on the headlights it shows a discharge.  Both alternator and Voltage regulator were recently check and both are good.  I just need an explanation of what/how many wires go where.  I think I might have some wires on wrong studs.  The letter U is the amp gauge.  Thanks in advance.

[36humpback]

I'm having trouble wiring up the back of the ammeter on my 36 Dodge panel.  The wiring diagram is so grainy that I can't tell what wire goes where.  There are three studs on the back.  One above the the fuse and two below. the attached pic shows a stud next to fuse.  Is this the one above the fuse on my ammeter? With engine running the ammeter does not show charging, but when I turn on the headlights it shows a discharge.  Both alternator and Voltage regulator were recently check and both are good.  I just need an explanation of what/how many wires go where.  I think I might have some wires on wrong studs.  The letter U is the amp gauge.  Also a pic of the back of the amp gauge. Thanks in advance.

Edited March 13 by 36humpback (see edit history)

[Bloo]

There is a 36 Chrysler thread by @Professor where the ammeter was discussed. Ammeter conversation starts near the bottom of page 8 and continues on page 9. There are some pics of the back of an ammeter.

 

https://forums.aaca.org/topic/344725-1936-chrysler-airstream-c-8-convertible-restoration/page/8/

 

More or less, a wire comes from the generator and feeds the (+) ammeter terminal. The ignition switch and the fuseholder are fed from this (+) terminal. On the fused (opposite) side of the fuseholder the stoplight, light switch, and dome light are connected. The remaining terminal (ammeter - ) feeds the wire to the battery (via the starter post) and the cigarette lighter if there is one.

 

 

 

[36humpback]

3 hours ago, Bloo said:

There is a 36 Chrysler thread by @Professor where the ammeter was discussed. Ammeter conversation starts near the bottom of page 8 and continues on page 9. There are some pics of the back of an ammeter.

 

https://forums.aaca.org/topic/344725-1936-chrysler-airstream-c-8-convertible-restoration/page/8/

 

More or less, a wire comes from the generator and feeds the (+) ammeter terminal. The ignition switch and the fuseholder are fed from this (+) terminal. On the fused (opposite) side of the fuseholder the stoplight, light switch, and dome light are connected. The remaining terminal (ammeter - ) feeds the wire to the battery (via the starter post) and the cigarette lighter if there is one.

 

 

 

Thanks BLOO for the info.  Attached is a pic of the back of the amp gauge.  I figure the + terminal is the one on the bottom right and says gen below it.  The one on the bottom left says BAT.  What, how, hooks up to it?  The rest of the wires hook up on the other side of the fuse?

[Joe Cocuzza]

[Bloo]

The way that is marked makes no sense to me. The little piece of wiring diagram you posted looks like the Chrysler in the linked thread, as near as i can tell, but the ammeter in the picture here makes no sense.

 

Most of the loads connect to the fuse (top terminal), but the fuse should be fed from the GEN side. Is there any possibility that the strap to the fuse might reach the GEN post instead of BAT and somebody just moved it to the BAT post?

 

Ignition should also feed from the GEN side.

 

EDIT: Just found the other thread in "general" where @Joe Cocuzza posted the wiring diagram:

 

https://forums.aaca.org/topic/412598-help-wiring-back-of-ammeter/#comment-2656465

 

 

 

 

Wire 7 (generator) and wire 24 (ignition) and the fuse strap are all connected to the lower left (in your picture of the ammeter) post. All other loads, wire 28 and 3 others, are connected to the fuse (top post in your picture), and wire 17 goes from the lower right post (in your picture) to the starter post.

 

All that is as expected and makes sense except for the GEN and BAT marks stamped in  the ammeter which are apparently backwards. I would connect it as in the paragraph above and try it. The worst that could happen is that the ammeter will read backwards, and if it does, you will have to reverse the connections, lower right to lower left (in the picture) including that strap that feeds the fuse.

 

 

Edited March 13 by Bloo (see edit history)

[TerryB]

You mentioned alternator and voltage regulator, has you replaced the stock generator and cut out relay?  With the meter showing discharge with the headlights on would indicate the wiring is somewhat correct, especially if this happens at idle.

[Bloo]

Wait what? Is it not 6v positive ground anymore? If true, that would have been good to know. It would explain why things are all backwards in the other thread.

 

https://forums.aaca.org/topic/412600-help-wiring-back-of-amp-gauge/

 

 

Edited March 13 by Bloo (see edit history)

[36humpback]

24 minutes ago, Bloo said:

Wait what? Is it not 6v positive ground anymore? If true, that would have been good to know. It would explain why things are all backwards in the other thread.

 

https://forums.aaca.org/topic/412600-help-wiring-back-of-amp-gauge/

 

 

Thanks for the additional info,  The pic is one I got of the interweb.  I'll contort my aged body today and see what the back of mine looks like.  It is still a 6 volt, but I do have a newer generator installed.

[36humpback]

40 minutes ago, TerryB said:

You mentioned alternator and voltage regulator, has you replaced the stock generator and cut out relay?  With the meter showing discharge with the headlights on would indicate the wiring is somewhat correct, especially if this happens at idle.

I meant to type generator not alternator.

[36humpback]

2 hours ago, 36humpback said:

Thanks for the additional info,  The pic is one I got of the interweb.  I'll contort my aged body today and see what the back of mine looks like.  It is still a 6 volt, but I do have a newer generator installed.

Ok... Here is what the instructions I have for the wiring harness say: 

# 15 ammeter (same terminal as wire # 18, 24, 29, 32) to starter switch "BAT"

#16 VR "bat" to ammeter

#18 Ammeter to horn

#24 Ammeter to cab light switch

#29 Ammeter to instrument light switch

#31 ammeter(same terminal as wire #16 to ignition switch

#32 ammeter( same terminal as wire # 15, 18,24,29) to headlight switch (bat)

#52 ammeter to heater switch

The back of my ammeter is the same as the pic I got off the interweb, except there are no gen or bat markings on it.

With these instructions, can you tell me what wires go where? I assume that "accessories" go to the top above the fuse.  My big question is #15, 18, 24, ,29, and 32 to starter switch bat. does that mean the bat on the VR?, and they all go on the bottom right stud?  Thanks.

[TerryB]

Is your voltage regulator just a cut-out relay mounted on or near the generator?  My 1937 Dodge pickup had the cutout on the top of the generator, just a single wire output that was then connected to the (-) battery lug on the starter. From there a wire went to the ammeter fuse and then the other terminals on the ammeter fed the ignition switch, the light switch and so on.  I think the reason for multiple terminals on the ammeter were to allow branching out the power (current) coming from the voltage regulator to the circuits that needed it rather than trying to tie all those together on a single terminal.  Note- the 1937 Dodge ownership was a long time ago and I’m going off my hazy memory.

[Bloo]

Well... Not exactly. Ammeters are flow meters. The wire from the generator needs to go to one ammeter post. The other ammeter terminal goes to the wire from the battery cable connection at the starter post. This is so the ammeter ONLY measures current (amps, flow) coming in or out of the battery.

 

If you connected the generator wire directly to the starter post, the truck would charge fine, but the ammeter wouldn't work correctly if at all. The ammeter can't measure flow that does not go through it.

 

On any car with an ammeter, the generator system needs to be connected to one side of the ammeter, and the battery to the other. Also, all lights, ignition, radios, heaters, and almost everything else connects to the GENERATOR side. This is because the generator is the source of current when you are underway, not the battery, and you want to drain off any current that is used by ignition, lights, etc. before that current has a chance to go through the ammeter. That way you only see current going into or coming out of the battery.

 

Exceptions to the "everything on the generator side" rule can sometimes be horns (GM usually put them on the battery side of the ammeter) and cigarette lighters (Chrysler did this I think). These will register the wrong way on the ammeter, but they don't do it for very long so I guess it doesn't matter.

 

Based on the diagrams posted so far it looks like:

1) The generator, ignition, and fuse connect to one side. By "generator" I mean the wire  from either the cutout, or the BAT terminal of the voltage regulator if your newer generator has a voltage regulator.

2) The rest of the loads connect to opposite side of the fuse (except lighter if equipped).

3) The wire from the starter post (battery cable) goes to the opposite side of the ammeter.

 

That's all there is to it really. If by some chance it works backwards, reverse the ammeter connections. Remember it is a flow meter, so if it works backwards, the current is flowing through it in the wrong direction.

 

[Bloo]

4 hours ago, 36humpback said:

With these instructions, can you tell me what wires go where? I assume that "accessories" go to the top above the fuse.  My big question is #15, 18, 24, ,29, and 32 to starter switch bat. does that mean the bat on the VR?, and they all go on the bottom right stud?  Thanks.

I think they are ignoring the fuse. Those are all things that would connect to the fused side of the fuse (top in the pic). "Starter Switch Bat." makes no sense. In fact it sounds like the starter/battery connection that does not connect here.  "Bat on the VR" sounds right.

 

4 hours ago, 36humpback said:

#16 VR "bat" to ammeter

4 hours ago, 36humpback said:

#31 ammeter(same terminal as wire #16 to ignition switch

Yes. These should go to the ammeter terminal that is strapped to the unfused side of the fuse. Take a close look at yours. I think the ammeter picture from the internet might have the strap on the wrong post(?). Not sure about that.

 

4 hours ago, 36humpback said:

#52 ammeter to heater switch

Not sure if this should be on the fuse or not. If yes it goes on top with all the other accessories. If not, it goes on the ammeter post with the VR wire, the ignition switch wire, and the fuse strap.

 

The other remaining ammeter terminal connects to the wire to the starter cable.

 

 

 

 

Edited March 14 by Bloo (see edit history)

[36humpback]

29 minutes ago, Bloo said:

I think they are ignoring the fuse. Those are all things that would connect to the fused side of the fuse (top in the pic). "Starter Switch Bat." makes no sense. In fact it sounds like the starter/battery connection that does not connect here.  "Bat on the VR" sounds right.

 

Yes. These should go to the ammeter terminal that is strapped to the unfused side of the fuse. Take a close look at yours. I think the ammeter picture from the internet might have the strap on the wrong post(?). Not sure about that.

 

Not sure if this should be on the fuse or not. If yes it goes on top with all the other accessories. If not, it goes on the ammeter post with the VR wire, the ignition switch wire, and the fuse strap.

 

The other remaining ammeter terminal connects to the wire to the starter cable.

 

 

 

 

Thanks again for all the info Bloo.  Hopefully my last an maybe unnecessary question.  The fuse protects all the wires on the top post?  That's what I am thinking since power is coming from bottom.  I do have a two wire generator with a voltage regulator.

[36humpback]

4 hours ago, TerryB said:

Is your voltage regulator just a cut-out relay mounted on or near the generator?  My 1937 Dodge pickup had the cutout on the top of the generator, just a single wire output that was then connected to the (-) battery lug on the starter. From there a wire went to the ammeter fuse and then the other terminals on the ammeter fed the ignition switch, the light switch and so on.  I think the reason for multiple terminals on the ammeter were to allow branching out the power (current) coming from the voltage regulator to the circuits that needed it rather than trying to tie all those together on a single terminal.  Note- the 1937 Dodge ownership was a long time ago and I’m going off my hazy memory.

Voltage regulator mounted on the firewall.

[Bloo]

3 hours ago, 36humpback said:

Thanks again for all the info Bloo.  Hopefully my last an maybe unnecessary question.  The fuse protects all the wires on the top post?  That's what I am thinking since power is coming from bottom.  I do have a two wire generator with a voltage regulator.

Yes, that's the idea.

[TerryB]

Just to add for hopefully clarification, the battery connection on the starter is on the open side of the mechanical starter switch at least on the truck I had.  The starter button is the foot activated push button right above the gas pedal. Press that button and a mechanical linkage will connect the (-) battery to the starter.  In my 1937 case, this connection terminal for the battery cable provided the common point for the generator to battery and the connection to  to the ammeter.

[36humpback]

UPDATE  I got the amp gauge to go to + side when engine is reved up.  Yeah!! Now I have to figure out what terminals all the other wires go to.  I have most everything else fastened to the generator lug. No headlights, or panel lights.

If I understand all the comments correctly, the following wires go on the top stud.

15,

18- ammeter to horn

24- ammeter to cab light swirch

29- ammeter to instrument light switch

32- ammeter to headlight switch

Any and all help appreciated.  Thanks, Bob

Edited March 15 by 36humpback
added info (see edit history)

[Bloo]

I believe those go on the fuse lug (based on the wiring diagram).

 

The fuse itself should be fed from the generator lug.

[36humpback]

10 hours ago, Bloo said:

I believe those go on the fuse lug (based on the wiring diagram).

 

The fuse itself should be fed from the generator lug.

Mine and the pic both show fuse fed from left bottom lug. the web pic shows it as BAT. If I switch my wires on those two, wouldn't it show discharge instead of charge when revved up?

[Bloo]

1 hour ago, 36humpback said:

Mine and the pic both show fuse fed from left bottom lug. the web pic shows it as BAT. If I switch my wires on those two, wouldn't it show discharge instead of charge when revved up?

Well... The fuseholder clouds the issue. There are two factors at work.

 

The first thing is that the ammeter indicates flow. With no accessories connected, if the ammeter reads backwards when the generator is charging the battery, it is connected backwards. Reverse the leads.

 

The second thing is the accessories. They need to be connected to the generator side of the ammeter. This can be via a fuse or not via a fuse. In this case a fuse was used, but that is not important. What is important is that any accessories connected to the battery side will draw current through the ammeter. Will the truck work like that? Yes. The trouble is that any current those accessories use registers as "charge". It makes the ammeter almost meaningless, because if the accessories draw more than the generator can supply, the battery will still go dead. You have no idea whether the battery is being charged or discharged. The ammeter would still go to the center if the generator quit entirely, so there's that I guess.

 

The wiring diagram posted shows the fuse and accessories connected to the generator side as normal. That was also true in Professor's 36 Chrysler thread. That is the left lower lug on the diagrams (with the whole gauge spun 90 degrees to the right). It is the "gen" and "bat" stampings on the web pic that appear wrong.

 

1 hour ago, 36humpback said:

Mine and the pic both show fuse fed from left bottom lug. the web pic shows it as BAT.

Yes. There's the rub.

 

19 hours ago, 36humpback said:

UPDATE  I got the amp gauge to go to + side when engine is reved up.  Yeah!! Now I have to figure out what terminals all the other wires go to.  I have most everything else fastened to the generator lug. No headlights, or panel lights.

If I understand that correctly, you have only the wire to the starter connected to one ammeter post, and the generator and anything else currently hooked up to the other ammeter post, and it shows a charge when revved, right? If so, it is working normally.

 

Never mind right or left. Is the fuse's brass strap connected to the same ammeter post that is connected to the generator right now? If so, it's all good.

 

 

Edited March 15 by Bloo (see edit history)

[36humpback]

1 hour ago, Bloo said:

Well... The fuseholder clouds the issue. There are two factors at work.

 

The first thing is that the ammeter indicates flow. With no accessories connected, if the ammeter reads backwards when the generator is charging the battery, it is connected backwards. Reverse the leads.

 

The second thing is the accessories. They need to be connected to the generator side of the ammeter. This can be via a fuse or not via a fuse. In this case a fuse was used, but that is not important. What is important is that any accessories connected to the battery side will draw current through the ammeter. Will the truck work like that? Yes. The trouble is that any current those accessories use registers as "charge". It makes the ammeter almost meaningless, because if the accessories draw more than the generator can supply, the battery will still go dead. You have no idea whether the battery is being charged or discharged. The ammeter would still go to the center if the generator quit entirely, so there's that I guess.

 

The wiring diagram posted shows the fuse and accessories connected to the generator side as normal. That was also true in Professor's 36 Chrysler thread. That is the left lower lug on the diagrams (with the whole gauge spun 90 degrees to the right). It is the "gen" and "bat" stampings on the web pic that appear wrong.

 

Yes. There's the rub.

 

If I understand that correctly, you have only the wire to the starter connected to one ammeter post, and the generator and anything else currently hooked up to the other ammeter post, and it shows a charge when revved, right? If so, it is working normally.

 

Never mind right or left. Is the fuse's brass strap connected to the same ammeter post that is connected to the generator right now? If so, it's all good.

 

 

The generator is hooked up to the lug on the right. (not to fused lug), and is working properly for charging.(going positive when revved up)

[Bloo]

Well then that's the correct connection of the ammeter. This truck is still 6 volts and positive ground, right?

 

If the fuse (and accessories) then connect to the battery side, you can expect all current drawn by accesories and lights to be "charge". In other words, when the engine is running anything you turn on will make the meter go to "charge". Of course it isn't charge, it's just the current coming from the generator, some of it going to whatever you turned on, some going to the battery maybe... or maybe not.  If the generator stopped charging entirely, nothing would register "charge" anymore. It would be like having an idiot light. Better than nothing I guess.

 

Honestly I don't know what to make of it. When I saw the internet ammeter picture initially, I assumed someone had modified it for a negative ground conversion (probably 12 volt) by moving the strap. The strap even has a bend in it that makes it look like it has been moved. Now that we know yours is the same, I can't explain it.

 

Edited March 15 by Bloo (see edit history)