Charging problem?

grass1950January 18, 2013

I have a rider with a 1996 Linamar 790 (Onan p220) engine.
The battery was almost 10yrs old and when the engine was running the ammeter would normally read "0" unless the lights were in use. Every so often (lights off) the ammeter would read +"10" for a minute or so, but very seldom. The old battery died this winter and was replaced. Now when the lights are on, and the ignition is in the "on" position with the tractor not running, the ammeter reads -"10" and when the tractor is started the ammeter reads -"7.5". With the lights "off" and the ignition in the "on" position, the ammeter reads -"2.5" and once the tracter is running, the ammeter reads "0".
Is there a charging problem or is this normal? I do not own a multimeter. Thanks.

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bill_kapaun

IF your readings are accurate, your charging system is providing 2.5 Amps and your engine requires EXACTLY the same amount to operate.
Therefore- you would be discharging the battery some every time you-
Start
Use lights
Leave the key on.

Were your observations @ HIGH engine speed? It makes a difference.

Only other possibility is an inaccurate ammeter.

This post was edited by bill_kapaun on Fri, Jan 18, 13 at 14:10

    Bookmark   January 18, 2013 at 2:09PM
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tomplum

You may want to check with an external multimeter to verify. It seems that is what Bill concerned with is to know rather than assume what the ammeter in the dash says is so. You can compare the results off, running, running w/ various loads and even perform a draw test easy enough.

    Bookmark   January 18, 2013 at 3:05PM
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grass1950

Reading is the same regardless of engine speed. Since the installation of the new battery, I have not seen a reading into the posive range. Is there any significance to be seen in that with the old battery the ammeter would occasionally/rarely read +"10" for a minute or so? It appears I may need to shell out for a multimeter. Any suggestions for an inexpensive one I might get at autozone etc that would do the job?

    Bookmark   January 18, 2013 at 3:21PM
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bill_kapaun

Just a cheap multi meter will work.

IF it's charging, the voltage to the battery should rise to around 14ish Volts @ high engine speed.

A FULLY charged battery should read about 12.6 V.

    Bookmark   January 18, 2013 at 5:23PM
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exmar

To restate what's been said. I'd put an inexpensive volt meter across the battery when the engine isn't running. Let's say it reads 12.X volts, start the engine the voltage should rise ABOVE the non running reading. That would indicate the chargine system is working. The 14.6V Mr. Bill mentiioned is valid, however given the age your charging system could be suspect, did you go through and clean up all connections, including grounds? When you replaced the battery, is it the same size or larger? Remember these engines are designed to spend most of their lives running at WOT (Wide Open Throttle) mowing.

Good luck,

Ev

    Bookmark   January 19, 2013 at 12:26PM
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wertach zone 7-B SC

If you don't want to buy a meter and have a way to haul it. The place that you bought the battery from will probably test it for free.

    Bookmark   January 19, 2013 at 2:15PM
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bill_kapaun

Not sure where I said ANYTHING about 14.6V????????????

It's irritating to be misquoted!

    Bookmark   January 19, 2013 at 3:56PM
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exmar

Sorry Mr. Bill,

Ev

    Bookmark   January 19, 2013 at 5:04PM
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txtom50(8a texas)

Back to a cheap multimeter source, Walmart has a GE digital model in stores for about $18.00.

    Bookmark   January 20, 2013 at 5:25AM
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grass1950

I now have a multimeter. Checked batery voltage (terminal to terminal). Reading 12'6 v. Started engine and took new reading. At both low idle and high rev. Reading is 12.4 v. Turned off engine. Took reading. Reading is 12.4 v initially, but one hour later, reading is 12.6 v.
Checked all connections and wires as well as I could. All connections and wires appear good. The tight space and covered harnesses do not help. Regulator has two AC wires (black) comming from stator and one middle wire (white or grey) from regulator going to a multi wire plug connector and then becomming a multi wire harness. Schematic appears to show a red wire within the harness going from the multi wire plug to ammeter then to the starter. (It doesn't help that I'm color blind)
How might I go about checking if the stator is good first, then check the regulator?
All help appreciated

    Bookmark   January 28, 2013 at 2:32PM
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grass1950

Found instruction on checking stator and regulator. Voltage reading at the DC pole of the regulator while running at 3600 rpm is 3.8V. Reading of the left AC wire coming from the stator is 31V. Reading on the right AC wire coming from the stator is 6V. Checked stator continuity and no short was indicated. Checked resistance between the two Stator AC wires and got 1.8-2.6 ohms using the 0-200 scale on a very inexpensive multimeter that has a stated accuracy of 1-2% + or - 2D for most measurements, so I'm guessing that the ohms reading I got is not very dependable. Any ideas as to why the variation in AC voltage between the two stator leads? Or where the charging problem may lie?

    Bookmark   January 28, 2013 at 7:56PM
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bill_kapaun

Did your instructions give actual numbers to meet specs?

IF you have a lower OHMs scale, use it. Although, if it's a 2.0 scale, it'll probably over range.

Are you sure the instructions didn't say to check ACV BETWEEN the 2 AC outputs. (not individually to ground)
I have a hunch your 6 V on one is VERY suspect though.

Your +/- 2 digits really doesn't mean that much. It's only .2 MAX. Your variance is not untypical of measuring LOW OHMs. Radio stations etc. are broadcasting to your antenna (leads).

    Bookmark   January 28, 2013 at 8:16PM
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grass1950

Well, the instructions I found do give spec ranges, but I'm not real sure which I'm to use. For instances their are 2 different specs for 20 amps and another for 35 amps. they range from .06-.1 ohms (for 20 and 35 amp systems) and .1 to.19 ohms for the other 20 amp system. It does say to run from AC lead to ground to sest volts and rec specs vary there too. from anywhere from 21VAC @1800 RPN to 57 VAC @3600 RPM.
Here's the link if you are interested in a look (Starts on page 8-5: http://home.comcast.net/~lyon.family1/WheelHorse/Onan_Engine.pdf

BTW, a reading across the two AC leads is about 32VAC.

Thanksfor your input.

Here is a link that might be useful: Onan/Linamar

This post was edited by grass1950 on Mon, Jan 28, 13 at 21:05

    Bookmark   January 28, 2013 at 8:58PM
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bill_kapaun

"It does say to run from AC lead to ground to sest volts ......."

It does??? I guess I missed that part.

In any case, if you are only getting 32V @ high engine speed, it's a FAIL in any case.

    Bookmark   January 29, 2013 at 5:58AM
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grass1950

No, you didn't miss anything. You just can't read into things like I can. Crap. I hope my misunderstanding of the proceedure did no harm.
The 32VAC was at half throttle. Full throtle (approx 3600 RPM) was used to check DCV.
I'll check the ACV ACROSS the stator leads today at FULL throttle.

Thanks for your help Bill.

    Bookmark   January 29, 2013 at 7:52AM
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grass1950

The VAC reading across the stator terminals at full speed is 54.5VAC. Fail? As to your inquiry regarding the resistance test, my multimeter is an inexpensive Cen-tech digital and does not have a scale below 200. The specs call for measurement to fall between hundreths and tenths.

    Bookmark   January 29, 2013 at 8:58AM
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bill_kapaun

With 54.5V, it's 99% sure you have the "Spec B" system.
That states APPROX 57 V, so you are within 5%.

I think I'd bite the bullet and spring for a new VR.

I've never heard of a bad stator putting out too much, but then again I'm not in the business.
Maybe someone else can chime in if they've ever heard of that.

For your OHMS reading-
Did you touch the leads together to check the resistance of them and subtract that amount from the final reading?

This post was edited by bill_kapaun on Tue, Jan 29, 13 at 10:37

    Bookmark   January 29, 2013 at 10:35AM
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grass1950

"Did you touch the leads together to check the resistance of them and subtract that amount from the final reading?"

No I didn't. I did check for zero at 200k scale. (Manual says to check for zero at 200w--not sure what scale that is.) At 200 scale, I get 2.4ohms (it bounces from 2.4 to high 40's, but if I'm patient I can get a stable 2.4) If I subtract that from the readings I got while testing the stator I get a neg to zero sum.
Should I wait to see if anyone chimes in on the staor issue, or just bite the bullet? If the stator is bad, I really hate to spend money for the VR as I don't think I want to go to that much work and expense to replace the stator and/or the flywheel/magnets--we'll see I guess. I know I can't get a stator locally, I'll search the internet and see what comes up. The VR I can get nearby.

BTW, what parameters are used to determine when the VAC of the stator is fail or pass.?

Thanks again Bill.

    Bookmark   January 29, 2013 at 12:01PM
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bill_kapaun

Briggs for example, will specify a minimum number.
I don't know how much you can fudge under the minimum and still work.
Hopefully, someone will chime in that actually works with these.

You might try Googling. I know a similar issue has been discussed on a different forum that results in banishment from this forum if mentioned.

    Bookmark   January 29, 2013 at 4:30PM
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grass1950

Replaced the VR (expensive item -$98 most places, but found one for $78- for the Onan/Linamar) and all is working as it should now (DCV @ battery when running is now at 14+ DCV).

I wasn't able to find any info as to how much under the recommended stator output would still be sufficient for adequate charging. I did find info that for a given stator and magnets that the only way output can increase is through increased RPM.
Thanks for your help on this Bill.

    Bookmark   February 5, 2013 at 10:16AM
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bill_kapaun

Glad it's fixed.
I always hate to recommend for someone else to spend their money unless the outcome is sure. A $2 spark plug is one thing, but we're talking serious $ here.

    Bookmark   February 5, 2013 at 10:36AM
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grass1950

I still have that one questing: What scale is used to measure ohms in the hundreths to tenths range? As I said, my multimeter has a 200k and a200 scale. I'm not sure eiter is sufficient.

    Bookmark   February 7, 2013 at 11:18AM
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bill_kapaun

It would be your LOWEST OHMS scale, but also would be somewhat dependent on the number of digits your display has.
IF the leftmost digit is either 0 or 1, that is called "a half digit".
If you have 3 positions that read 0-9, that meter would have a 3-1/2 digit display.
Therefore- you would only have ONE digit to the right of the decimal point and could only read tenths of an OHM. (you theoretically would be able to read 000.1 to 199.9 on the 200 OHM scale)
Add in the accuracy of the meter +/- 1 digit and your meter really isn't suitable for reading that range.
You are also reading on the EXTREME bottom of the range, where accuracy would be more questionable as compared to the "middle" of the range such as 100 OHMS.

    Bookmark   February 7, 2013 at 2:17PM
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