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6 volt/12 volt? - NOT "How do I convert to 12 v"

S

sflem849

Well-known Member
I went to pick up my SMTA from a custom plow job this afternoon and it wouldn't start. I tried to jump it with my pickup (7.3 powerstroke with two brand new batteries at 880 CCA each) and it wouldn't go. There were sparks when I hooked it up so it must have been a decent connection.
So out comes the chain. It popped quickly at the first try. I drove it home which took about 15 minutes. It wouldn't restart at home when shut down so I hooked the charger to it and it would go on boost.
I got the multimeter out and it showed 7.00 volts. Hmm. That seems to me what a 6 volt should put out. I check the internet and sure enough, it is.
What is going on here? Shouldn't a 12 volt generator put out 12 volts no matter how low the battery is? Do you think they gave me a 6 volt gen instead of a 12 volt? Any additional checks or thoughts?
 
Who gave you a 6v generator? Have you replaced the generator lately? If so, give us all the facts.......
mike
 
Sorry, I didn't want to get too wordy :)
I replaced the generator with one from NAPA about four years ago. When I bought the tractor from my FIL NOTHING electrical worked like it was supposed to. I replaced the generator with a rebuild, put a new regulator on, and had the starter rebuilt. I did the jumper wire thing at this time.
The tractor is hooked up positive ground and the ampmeter read backwards after all my electrical work so I switched the wires around. It never moves more than 1/4" from the center, EVER. I have only done the jumper wire thing once.
The lights were really dim when I turned them on. I assume this is bc they were only getting 7 volts.
 
interesting.... did you ever put a volt meter on it before hand? take the hood off and see if there are any markings on the genny....
 
The voltage regulator is what determines what the charging voltage will be. If you use a six volt regulator with a twelve volt generator you will end up with voltage to charge a six volt battery, about seven volts. Likewise if you use a twelve volt regulator on a six volt generator you will see voltages high enough to charge a twelve volt battery, at least for a little while.
 
Hi... I'm not sure I'm following you very well but, I think you saying you have a 12 volt battery and you are measuring 7 volts at the battery?
If you got 6 volt generator 4 years ago, I would think the battery would have run down long ago. Seems more likely you have a bad regulator, generator or bad cells in the battery. Since you charged the battery with a battery charger and you are only seeing 7 volts at the battery, I'd get the battery tested first.
Pete
 
I would have to throw the tractor on the charger about once per year since I bought it. I figured this was just bc I didn't use it for much more than tractor pulling.
I actually had the tractor on the charger over night. I have to go do chores now and I will report back. I will test the battery voltage before starting and while running.
 
If you went to NAPA and said, "Give me a replacement generator for a Super MTA," they sold you a 6 Volt generator.

It won't start because you have bad battery connections somewhere...
 
(quoted from post at 07:01:46 12/19/09) If you went to NAPA and said, "Give me a replacement generator for a Super MTA," they sold you a 6 Volt generator.

It won't start because you have bad battery connections somewhere...
Click to expand...

My uncle was the manager for the location and I worked on him with it. I remember him asking if it is 6v or 12v system. Could have been misboxed or ???. Both VR and generator came from NAPA.
Didn't start bc the battery was dead. It was WAY below 12 volts on the DMM. Connections look decent with no noticable crud.

I checked the battery this morning (after being on charger) before starting and it was 12.75 volts. I then started the tractor and it was 12.03 volts. Probably dropped when cranking by .75 volts.

[b:ac835a0df1]What is my next step?[/b:ac835a0df1]
Am I on to something with improper VR or Gen?
How do I check VR?
Will a bad VR still put out some volts and it just happens to be 6v capacity?
How do I check gen?
Should I redo the jumper wire thing? What two terminals?

(quoted from post at 18:28:16 12/18/09)...Since you charged the battery with a battery charger and you are only seeing 7 volts at the battery, I'd get the battery tested first.
Pete
Click to expand...
Sorry, the 7 volts was on the battery before charging and after pull starting with 15 minute road trip at full throttle.
After charging 20 amps for 2.5 hours the battery voltage was 12.75 volts. After cranking with engine running it was 12.03 volts. I am not sure about a tractor, but my pickup puts out about 13.6-14 volts when running.
 
I doubt it's the wrong VR or generator. You would've had problems a LONG time ago.

At 7 Volts, though, that battery is SHOT. 12V batteries are permanently and fatally damaged if they go under 10.0 Volts. It may last a while if you start and run the tractor every day, but not forever.
 

Put a new / another battery in it if you can....a poor battery won't even boost start...
 
(quoted from post at 22:02:39 12/19/09)
Put a new / another battery in it if you can....a poor battery won't even boost start...
Click to expand...
f you have big enough jumper cables it will........even if it has no battery at all
 
I guess I wasn't clear, the tractor starts and runs fine now that I charged it.
The problem is it doesn't seem to be charging. Checking the voltage with it running I only see 12 volts. IIUC a 12v system should be near 13.6-14.
What I am saying is it is only recieving 7 volts before charging. How do I know if this is from the charging system or if that is what the battery had in it when I checked it? The real question is how do I know if it is charging. In my head it seems like even if the battery was dead it should still read 12+ if the tractor was running bc the gen is putting out that much voltage. Do I have a problem? (besides the battery, I know this is probably bad now, but there had to be something that caused this problem. I will load test that when I get it to a tester)
I forgot. If I do have a problem how do I isolate it without just throwing parts at it starting with a VR then to a battery then to ???
 
IF you do NOT have a magneto system.
With the tractor running at mid throttle disconnect the ground cable from the battery and if it keeps running the generator is working.
Dell
 
In my head it seems like even if the battery was dead it should still read 12+ if the tractor was running bc the gen is putting out that much voltage.
Click to expand...
Even if the charging system is working properly, a dead or weak battery can pull the generator output voltage down to whatever minimum voltage is required to push current back into the battery.

I don't recommend unhooking the battery on a running engine to see if it keeps running. There are non-destructive tests that can determine the same thing. Measure the voltage at the battery with the engine and all switches off. Measure the voltage again at a fast idle. If the second voltage reading is higher than the first, the charging system is working.
 
(quoted from post at 18:41:09 12/20/09)
In my head it seems like even if the battery was dead it should still read 12+ if the tractor was running bc the gen is putting out that much voltage.
Click to expand...
Even if the charging system is working properly, a dead or weak battery can pull the generator output voltage down to whatever minimum voltage is required to push current back into the battery.

I don't recommend unhooking the battery on a running engine to see if it keeps running. There are non-destructive tests that can determine the same thing. Measure the voltage at the battery with the engine and all switches off. Measure the voltage again at a fast idle. If the second voltage reading is higher than the first, the charging system is working.
Click to expand...

That is what I was trying to say I was doing. I tested it more today and running or not no matter what the throttle is set at it is putting out 12 volts. This tells me it is not charging. I polarized the VR and got the spark and click, but still nothing changed chargewise.

Is it possible to make sure it is not a 6 volt VR as opposed to 12 volt? I don't run it much, hardly any field work so it could run a LONG time on just the battery. Like I said, I have to charge it about once a year bc it will die.

I forgot, I am running a coil so I need a battery in place to run the tractor. It is a SMTA.
 
Most regulators are (or were when new) labeled to indicate voltage. They were also labeled for polarity, if it mattered. The marking may be stamped in or printed on. It is usually on one of the mounting brackets or somewhere on the bottom side. Most Delcos have it stamped into one of the mounting brackets. There will be some combination or 6 or 12, maybe a V and maybe a P or N. Maybe be POS or NEG. Might say "P 6V" or simply "12N".

There is a troubleshooting procedure on a web page. I don't have the pointer handy, but somebody usually posts it on any charging problem thread. I would expect a 6-volt regulator to test as "bad" if mounted on a 12-volt system.

One quick test is to directly ground the generator "F" terminal. Check voltage at the "A" terminal. This bypasses all the regulating function of the regulator and should put the generator at full output. Check voltage at the "A" terminal. If this voltage is above what you measure at the battery, the regulator is bad.

I am assuming you have good grounds everywhere, including the generator shell and the regulator.
 
(quoted from post at 20:27:29 12/20/09) Most regulators are (or were when new) labeled to indicate voltage. They were also labeled for polarity, if it mattered. The marking may be stamped in or printed on. It is usually on one of the mounting brackets or somewhere on the bottom side. Most Delcos have it stamped into one of the mounting brackets. There will be some combination or 6 or 12, maybe a V and maybe a P or N. Maybe be POS or NEG. Might say "P 6V" or simply "12N".

There is a troubleshooting procedure on a web page. I don't have the pointer handy, but somebody usually posts it on any charging problem thread. I would expect a 6-volt regulator to test as "bad" if mounted on a 12-volt system.

One quick test is to directly ground the generator "F" terminal. Check voltage at the "A" terminal. This bypasses all the regulating function of the regulator and should put the generator at full output. Check voltage at the "A" terminal. If this voltage is above what you measure at the battery, the regulator is bad.

I am assuming you have good grounds everywhere, including the generator shell and the regulator.
Click to expand...

I will pull the VR tomorrow.

That is what I am worried about. I hate to toss a good VR. I find it hard to believe it could only last a handful of years.

That makes sense. Field to tractor frame to ground it out. Check voltage at Arm by touching one lead to arm and other to ground. Sounds like I need an extra pair of arms!
 
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