New question regarding firing up my 251 on the run engine stand.

[harmony]

I've sorted out most of my issues thanks to you guys.  I've got my 251 with fluid drive all wired up and everything sort of checks out.  I can hit the start button and the engine turns over and I have spark to the plugs. I've also polarized the regulator.  Basically all I have to do is add some fuel.  I've filled the cooling system and no leaks there.

But I'm trying to cross all my "T's" and dot all my "I's"  and make sure I've got it right.  I was re-watching an old "Master-Tech film clip "1948 Volume 1-6  Volts Amps and Ohms".  Something was said in that film clip caught my attention. 

 

Remember I'm just running the essentials on this run engine stand.  Well a little more than essentials because I want to test all the circuits.  So I've wired in the Regulator, Trans Relay, Governor switch, Trans Solenoid switch and the Interrupter switch.   But normally, as in the complete wiring diagram,  coming off the Ammeter you have a wire going to the cigar lighter, and another wire going to the light switch.  Also on the ignition switch on the one post you have a wire going to the back up light, turn signal flasher, horn relay, and the fuel gauge.  So that's a total of 6 wires that I'm not running, because I don't have any of those items.  

 

So in the Master-Tech film clip they say when doing a test "An ammeter has very little resistance, so if you connect it so it carries the full battery current itself without any resistance, it will burn out instantly".

 

To add to that though, I was reading the "Service Reference Book"  Vol 1 No.7 " reference to the Generator Regulator",   and on page 17 there is an illustration of a test being performed and it shows a resistor on one side of the ammeter. "

 

So my question is, since I'm not running any accessories (those 6 wires), do I need to protect the ammeter with a resistor?

Edited March 16, 2023 by harmony

[D35 Torpedo]

No. Having those items removed from the circuit is like having them turned off. It shouldn't affect the ammeter. Its job is to measure the difference in current between the gen and bat. The regulator is load sensitive. So it might help to have a load to verify its output above what the battery takes in.

[greg g]

The other option would be to wire in  a volt meter, and leave the ammeter out of play for test stand purposes.  Put an inline fuse in the wire going from  battery to ign switch, 20 amp should be sufficient

[Sam Buchanan]

Since you have no loads connected an ammeter is of no value to you. A voltmeter is much more useful because it shows not only the state of charge of the battery but also the condition of the charging system via how much the battery voltage is increased with the engine running. If you see 7.3-7.5v with the engine running your charging system is working properly. 

 

Matter of fact, some of us consider the voltmeter to be more useful in the car than an ammeter......but that is a topic for a different discussion. 

Edited March 16, 2023 by Sam Buchanan

[harmony]

D35 Torpedo:  That's exactly what I was thinking.  If all the accessories (so to say) are turned off, then it's basically the same set up as I have.  

greg g & Sam Buchanan.  I agree, I've always felt more comfortable looking down at the instruments and seeing a volt meter as opposed to an ammeter.

 

However,,,,  This '46 was equipped with an ammeter. I don't happen to have a volt meter kicking around the shop.  Plus I've wired in the original instrument panel, which makes economic sense to me.  As I've mentioned before I'm pretty thick headed when it comes to auto electrics so I don't really see the difference between what I've set up and the way it was when the engine, fluid drive and transmission were operating in the car, except for a bunch of body steel surrounding what I have here. 

But when "Master Tech" said the ammeter would basically blow up without a load on it, I got confused, which is why I've enquired here. 

 

I've added a few pictures of my set up,,,,, and yes,,,,, the wiring will be tidied up in a loom once I'm finished.  Yes,,,,, I've only got a few different wire colours, but I didn't want to spend about $120 plus, just so I could have a rainbow of colours.  Instead, I used different colours of heat shrink on the #10 wire ends that I did have, to tell them apart.  Yes,,,,, the battery is on the floor and not in the battery box that I built for it.  That's because I borrowed it from my '48 Chrysler.  I'll buy a designated battery for it once I getting it running.  Yes,,,,, I have two battery leads for the negative side of the battery.  That's because I didn't have enough  0/0 cable to run both positive and negative.  But I did have a couple of long 12 volt cables (4/0) so I just doubled up on the negative side of the battery.  Finally, yes,,,,,  if this project is a success, I'll give the framework a coat of paint so it's all one colour.

 

Once again, as in the past, I'm sorry for giving everyone a stiff neck, but I'm not about to keep altering the dimensions of  regularly shot, run of the mill pictures taken from my run of the mill phone, just so they won't show up laying on their side on this forum, which seems to happen more often than not, at least for me.  

  

Edited March 16, 2023 by harmony

[Sniper]

50 minutes ago, harmony said:

But when "Master Tech" said the ammeter would basically blow up without a load on it, I got confused, which is why I've enquired here. 

 

I would have to see that video, but an ammeter with no load isn't going to blow up.  It will do nothing.

[harmony]

4 minutes ago, Sniper said:

 

I would have to see that video, but an ammeter with no load isn't going to blow up.  It will do nothing.

I'm not sure if I did this right Sniper.  But here is that film clip.  It's mentioned around the 15:30 mark.

 

[Los_Control]

I'm going to play stupid here.

 

Point being, if a generator was putting out full output ....it can fry a ammeter gauge.

More commonly seen with a 12 volt alternator conversion .... My alternator is 65 amps ..... many are over 100 amps.

 

Same time it is possible to burn out a ammeter gauge on 6 volts depending on the load you send through it.

 

Probably more common on a 12 volt conversion with a high amp alternator ...... Just as possible on a stock 6 volt wiring harness with too many amps being pulled through the gauge.

 

I'm only suggesting it is what goes through the gauge, 6 volt or 12 volt ....

Some people have ran 25 years with no issue using a ammeter gauge on 12 volts. .... The next guy needed headlights, heater, radio, fan .... burned the ammeter gauge to the ground.

While more common on 12 volts, is just as possible to do the same on 6 volts. ..... Not likely .... but possible.   @harmony has a honest question here.

 

While I do not know the exact answer here, I think if you run the headlights or other heavy loads after the ammeter .... the gauge simply reads the battery & current charge.

[Sam Buchanan]

1 hour ago, harmony said:

I don't happen to have a volt meter kicking around the shop.

 

Hope 'bout a new voltmeter for $7?

 

https://www.harborfreight.com/electrical/electrician-s-tools/multimeters-testers/7-function-digital-multimeter-63759.html

 

 

 

I have four or five of this things scattered all around so one is always handy. Even gave some away when they were free with a Habba Fright coupon.

 

 

 

Edited March 17, 2023 by Sam Buchanan

[harmony]

14 minutes ago, Sam Buchanan said:

 

Hope 'bout a new voltmeter for $7?

 

https://www.harborfreight.com/electrical/electrician-s-tools/multimeters-testers/7-function-digital-multimeter-63759.html

 

 

 

I have four or five of this things scattered all around so one is always handy. Even gave some away when they were free with a Habba Fright coupon.

 

 

 

I have a half a dozen of those gizmos I think.  I get tired of trying to find the one I lost in my shop so I go buy another.  Then one day I seem to spot 4 of them, by tripping over them.  Then the next day I can't find one, so I go buy another one,,,, and on and on it goes.

  

I was thinking about your suggestion, when I came across the illustration in the "service reference book" that I mentioned before, that shows the resistor ( see x in the illustration).  The volt meter is wired in after the ammeter at the B terminal on the regulator.  At that point I was thinking, "why not use a multimeter?  Then the whole idea slipped my mind until you just mentioned it.  Getting old is such a fun journey,,,  hahahaha!

Edited March 17, 2023 by harmony

[Sniper]

1 hour ago, harmony said:

I'm not sure if I did this right Sniper.  But here is that film clip.  It's mentioned around the 15:30 mark.

 

Ok, I see what was being said.  If the ammeter is the ONLY load it will burn out, that is true. 

[harmony]

1 hour ago, Sniper said:

 

Ok, I see what was being said.  If the ammeter is the ONLY load it will burn out, that is true. 

How would I know if it is the "only" load?  

[harmony]

Lets try this from another angle. 

How about I install a resistor where I have shown it in my wiring diagram below (red R)?  My wiring is the same as the factory wiring diagram without any bells and whistles like horn relay, lights, cigar lighter, etc etc.   

I have no idea what I'm talking about, but my idea sort of resembles that page from the reference book that shows a resistor.

If that would work, what size resistor do I need?

 

Awhile back my odometer wasn't lighting up on my modern car.  A few resistors had become unattached from the dash circuit board.  So I removed the dash and soldered in new ones which were 150 ohms.  I think I have some left over.  Will one of those work?

Edited March 17, 2023 by harmony

[Sniper]

10 hours ago, harmony said:

How would I know if it is the "only" load?  

If the ammeter was connected to the posts on the battery with nothing else in line then it would be the only load and would smoke.  If any other electrical device is connected (aside from wires) between the ammeter and either battery post you are ok.

[Sam Buchanan]

Think in terms of the shunt inside the ammeter as being a dead short (it actually has a small amount of resistance). Connecting the ammeter across the battery terminals would be similar to connecting a wire between the terminals....the smoke escapes as the shunt blows like a fuse element. But put any load (bulb, motor, coil, etc) in the circuit and the smoke stays in the wires.

 

Edited March 17, 2023 by Sam Buchanan