Electrical sleuthing

[jeffgreef]

Got an electrical problem, have no experience sleuthing DC vehicle electrical problems. I do have a volt/amp meter. This is for my 1950 Super A.

When I bought it recently, the previous owner told me that it was necessary to disconnect the battery after every use or else the battery would run down. Also, he said that he thought the starter motor was going bad because it was cranking slowly. And, I noticed that the amp meter never moves.

As you see from the pics, a 6 volt alternator was installed. I've confirmed that the battery is 6 volt.

The slow cranking starter could be a low battery or it could be undersized battery cables which look to me like standard auto 12 volt sized cables.

Why would the amp meter not move at all? How do I tell if it is broken? I read somewhere that some replacement meters are, in that person's opinion, poor quality. Are there better and worse ones around?

How would you go about sleuthing the gradual discharge of the battery? I think one person suggested it may have to do with diodes in the alternator.

Got the battery on a trickle charger now, it's showing exactly 6 volts. My volt meter measures amperage and resistance.

 

[Qapla]

View attachment 460795View attachment 460794View attachment 460793Got an electrical problem, have no experience sleuthing DC vehicle electrical problems. I do have a volt/amp meter. This is for my 1950 Super A.

When I bought it recently, the previous owner told me that it was necessary to disconnect the battery after every use or else the battery would run down. Also, he said that he thought the starter motor was going bad because it was cranking slowly. And, I noticed that the amp meter never moves.

As you see from the pics, a 6 volt alternator was installed. I've confirmed that the battery is 6 volt.

Is you tractor positive or negative ground?

Actually, I can not really "see" from the pics that the alternator is 6v - all I see on the label is a bright square and cannot read anything it may say - and I cannot "spot" a 6v one from a 12v one just looking at the case.

That said, on many of the older systems the ammeter is connected in series with the charging circuit. You could check to see if the meter is good by connecting it directly from the battery, through the meter to a known load - it should show a "discharge". If it does not, it is probably bad - they can be bad and still allow the power to flow. Also, with the voltmeter connected to the battery it should read 6v or sightly above when the tractor is just sitting. While cranking it most likely will read under 6v and once running it should read enough above 6v that you can see if it is charging or not.

I am not sure just where the starter is, but, is it possible that the starter is 12v and that is why it runs slow?

You mention that the cables look like they are "standard auto 12 volt sized cables" - if they are, they should be heavy enough since a 12v car system needs just as suitable cables as a tractor does. When you are cranking it, does any of the wires get hot or do you smell "hot plastic"? If you do then the cables may be undersized - if not, the cables are probably sufficient and the problem is either a weak battery or a starter that needs replacing.

BTW - does the tractor run?

To locate the power drain you might try using your test meter connected to the battery. Then, disconnect whatever items/devices you have one-by-one, reconnecting each one once it has been eliminated as the problem. You should be able to read a power drain if your test meter is sensitive enough.

 

[jeffgreef]

Thanks for your response Qapla. You're quite right, one can't see that it is a 6 volt alternator from looking at it, what I meant was simply that the generator had been replaced, and that as far as I know it is a 6v alt.

The tractor was running. Right now it is partly disassembled and 265 miles away, awaiting my next vacation or long weekend. It was running well when I was there, and always started with the starter, though it was cranking slowly.

It has a negative ground, the positive goes straight to the starter.

Next time I'm up there I will take the ammeter off and try what you said- I'll get a 6v light bulb and set it up in series with the meter and see if it moves. That's good info to know that they can allow current to pass even when they are not working.

I suppose the starter could be a 12 volt. I would wonder why a 12v starter was installed on a 6v system that was not converted to 12v, but stranger things have happened. I'm told that the 6v starters will operate fine on 12v, but I don't know if Int. used a starter designed for 12v whenever they began producing the units with that voltage. I suppose this could be one of those, I don't know how to tell.

The battery cables don't over heat when starting and I don't smell anything burning. I see the reasoning of larger cables with 6 volt systems- the lower the voltage the higher the amperage to do the same work- and undersized cables will restrict the amperage. But I think I'll explore other things before installing thicker cable.

The volt meter I have seems to be very sensitive, but I'm inexperienced with these. To test for a power drain as you suggest, do you mean measure voltage across the battery poles as I try disconnecting different components? Or test for amperage after the battery?

 

[DJ54]

If you have a decent starter/generator repair shop near, they could bench test the alternator, and tell you exactly what you have, and if there are any problems. Originally, those were positive ground systems.

I'm thinking if you have a set of jumper cables, you can put them on the battery to starter, and to chassis, like the cables are, then try starting it, and see if it turns it over any faster. Kind of like a larger set of battery cables, but then not. Of course, that really depends on the battery too, whether it is up to snuff. It may show 6V, but you don't know how many cranking amps. Pretty much take a battery tester to check that.

 

[LD1]

To say it "turns over slowly" may mean different things to different folks as "slowly" is a subjective term.

6v systems DO turn over slower than 12v systems. Just the way it is and has always been. But since the tractor always starts if the battery is charged, I dont think this is an issue.

So it sounds like the real issues are
1. You dont know weather the alternator is charging as the gauge dont work
2. Parasitic loss on battery when tractor is off causing a dead battery next time

To see if it is actually charging, with the tractor running, put a meter on the battery. A 6v system should be 6.3v on a full charge battery, and should read something above that, like 7-8v while running. If you are at or under 6.3v then you arent charging.

As for the battery drain, you need a meter capable of doing DC amps inline. Most digital meters that are capable of this are fused to 10A max, which should be enough, but if it isnt, you have a BIG drain on the battery and will blow the 10a fuse inside the meter and will have to replace.
But what you would do is set the meter to 10a inline accordingly, and disconnect a battery cable. Put one lead on the battery terminal and one on the cable you just disconnected. (thus inserting the meter inline with the circuit.) Only do this with the tractor and key off as if its on and/or you try to start the tractor, you will exceed 10a and blow the fuse.

Your meter should now be reading the amperage draw on the battery. IIRC the target is 50mA or less parasitic load on the battery. If you are above that, start unhooking things one at a time until you find the culprit.

 

[jeffgreef]

Thanks Gents.

DJ- I will look for an alternator shop. I wonder what it costs to bench test and repair an alternator, if necessary. I was thinking of converting to 12v but perhaps I won't if the 6v works fine. I'll try the jumper cable idea as well. I'm suspicious of this battery, which is on a trickle charger and showing 6v exactly.

LD1- by 'turn over slowly', I mean that it turns and stops on a compression stroke, then turns again and stops on the next compression stroke. It rarely, but sometimes, continuously spins. Fortunately the rest of it is in good enough shape that it starts pretty easily, sometimes on the second compression stroke.

Battery, on the bench, shows 6v and no more. Guess I'll try to have it tested. It's 2-1/2 years old and was not used frequently.

I have an old analog volt meter with a needle- not the digital variety. It will measure DC amps. I'll try what you said.

Thanks for the good advice guys. I'll let you know what happens.

 

[Soundguy]

I'd drop a working 12v bat and alt on there, change the coil, and have a work g machine. If starter needs some brush n bush n bearings, go for it.

6v alt wasn't original anyway

 

[farm boy00]

Thanks Gents.

DJ- I will look for an alternator shop. I wonder what it costs to bench test and repair an alternator, if necessary. I was thinking of converting to 12v but perhaps I won't if the 6v works fine. I'll try the jumper cable idea as well. I'm suspicious of this battery, which is on a trickle charger and showing 6v exactly.

LD1- by 'turn over slowly', I mean that it turns and stops on a compression stroke, then turns again and stops on the next compression stroke. It rarely, but sometimes, continuously spins. Fortunately the rest of it is in good enough shape that it starts pretty easily, sometimes on the second compression stroke.

Battery, on the bench, shows 6v and no more. Guess I'll try to have it tested. It's 2-1/2 years old and was not used frequently.

I have an old analog volt meter with a needle- not the digital variety. It will measure DC amps. I'll try what you said.

Thanks for the good advice guys. I'll let you know what happens.

Well that from my experience is what happens for a min then rolls over enough to start. I just got rid of my farmall h that was 6v. Did the same thing usually so I just towed started it. New owner bought a. Brand new 6v battery to come get it and it did it for a min then rolled over and fired fine

 

[DJ54]

The only complaint I've ever had with the original 6V system is the crappy voltage regulators they seem to put out anymore. It didn't seem to matter if it was a $70 Echlin from NAPA, or a cheapie from an aftermarket place, I was lucky to get one year of service out of them.

Pretty fortunate to have a great local starter/generator shop, and Les finally found some decent USA made no name VR's, for around $45. I put one on the one Super C, and another on the 240U back in '07, and are still working great. The other Super C still has the Delco-Remy VR on it, when Dad purchased it back in '75, and still works great.

But, the slow rolling over when it comes up against compression, is normally the tell tale sign of small cables, even with a good battery. When the 8V battery's came out, and were supposed to be the fix all for that problem, it still did it.

About 3 years ago, it was time for a new battery, and I decided to upgrade to 1/0 cables since I had inherited that tractor. All NAPA had in stock was 2/0 cable, so had them made out of that. With the new battery, and the large cables, it rolled over like my Farmall A, and my other Super C I'd done the same to 20 years ago. You'd think you were jumping it with 12 volts.

Here, the starter guy doesn't charge anything to bench test anything. But, when I, or anyone else take's something in to him, it normally needs something. Last alternator I took to him was off the 310B Case hoe I had, that someone had converted to 12V, with a single wire GM alternator. He had 3-4 setting on the shelf ready to go, and swapped for mine, and $35. And it has a 1 year guarantee.

 

[jeffgreef]

Starting to look like the battery is on its last legs. Been on a trickle charge 24 hours and reads exactly 6 volts- should read 6.25 at least if it's healthy. Think I'll pull the alt and starter, have them checked in a local shop, if there's anything wrong with the alt I'll do a 12v conversion. No sense replacing both the battery and alt at 6v.

Probably ought to rewire. Anyone know where I can get a wiring diagram for a Super A with distributor, not magneto?