520h over charging

[fishingstararlake 1]

I have a that is charge at 16.5 it will drop to 14 with the lights on.

I put the charger on it so the battery is at full charge.

cleaned the posts so the battery is not asking for it.

Every thing I could find about the onans is not charging at all

has any else seen this ?

any help would be great

Dan

[sorekiwi 761]

Try running a ground wire from one of the mounting screws of the regulator directly to the battery negative. You could just do it with a jumper wire to see if it makes a difference.

Sometimes the regulators dont get a good ground through all those sheetmetal bits.

[fishingstararlake 1]

I didn't add that to my first post but already tryed that.

[sorekiwi 761]

I didn't add that to my first post but already tryed that.

OK,- I'm out of knowledge now! Maybe Chuck (SOI) or someone else smart will see this an chime in.

There is some troubleshooting info in the Onan manual, have you looked at that?

[dbartlett1958 99]

How are you measuring the voltage? The tractor gauge or a multimeter? Gauges are known to be off sometimes.

[fishingstararlake 1]

multimeter at the battery terminals

[Save Old Iron 1,572]

Try this

Engine OFF

Ignition key in RUN

Measure the DC voltage at the battery terminal - then move the meter probe from the (+) battery terminal to the B+ terminal on the rectifier regulator unit.

With the ignition switch in the RUN position and the engine OFF - you should read the same battery voltage on the RR's B+ terminal, This assures you have a good connection from the battery thru the ignition switch to the output of the RR. The RR needs a good connection to "see" what the battery voltage is.

Beyond a corroded wiring issue on the ignition switchor the RR wiring connector, the classic faults of the 520 charge system are the 9 pin connector on the engine harness and the fuse holders in the charge circuit.

The fuse holders corrode

and the 9 pin connectors corrode and melt. Check them too.

[Challenger 27]

Both 520H's I had did the same thing. Overcharged but with lights on dropped to about 14.

If I recall my dealer, (a good one), said not to worry about it if it stayed in that range.

(I'm not a mechanic, what do I know!)

[Ken B 3,202]

How are you measuring the voltage? The tractor gauge or a multimeter? Gauges are known to be off sometimes.

My 520 reads same overcharge as yours. I put a multimeter on it this past summer and the meter reads 14ish volts while the tractors gauge is reading over 16. I haven't done anything with it as I trust my multimeter and the tractor has been fine all this time. This June at the Big Show I'll try to find a new gauge.

[fishingstararlake 1]

I had 12.2 at battery and 11.98 RR's B+ terminal.

my 9 pin melted a long time ago. I changed it to male and female pushon coneters.

[fishingstararlake 1]

My multimeter reads the same as my gauge 16.

I have to run my lights or frie my battery.

I should of posted this sooner but

this all started after jumping. It has a hard time starting at below 0

[Save Old Iron 1,572]

I had 12.2 at battery and 11.98 RR's B+ terminal.

Well...

that's a (12.2 - 11.98) nearly half a volt drop over a very short run of wire. Some degree of corrosion in the wires at the RR and ignition switch might be an issue. If you can safely jumper a wire directly from the B+ terminal on the RR to the battery (+) terminal, that would eliminate wiring and possible ignition switch corrosion. Be safe here, as you will have a live wire right off the battery terminal and a whole bunch of grounds near the RR B+ terminal.

Anything over 14.5 volts @ the battery will start to evaporate fill solution in the battery - possibly overheating the battery - warping the lead plates and eventually causing the battery to fail. A slightly high charge voltage is not so dangerous in cold weather as it would be in warmer weather. Slightly elevated charge voltage in cold weather actually helps a battery last longer.

Failing all the test above, the evidence is starting to point to a failed RR unit. RR's are widely available on ebay for less than $30.

[fishingstararlake 1]

I got 15.57 at the battery with both the jumper in place and with it out

The test was done at 2200 rpm

[tiggercl 28]

Could this not be a symptom of a dodgy regulator / rectifier ?

Paul

[Save Old Iron 1,572]

Could this not be a symptom of a dodgy regulator / rectifier ?

Paul

Yes sir, I am now convinced that is the culprit.

[fishingstararlake 1]

what is a dodgy regulator?

Looks like I might have fried the regulator.

[Save Old Iron 1,572]

dodgey = a polite way of saying defective

[fishingstararlake 1]

found a replacment for 20 bucks on ebay

thanks for your help

Dan

[fishingstararlake 1]

replaced my dodgy r/r today. that was it

 

Thanks for the help

 

Dan

[Tankman 3,523]

Lots of good Sparky "stuff" here. Thank all for the replies.

I'm marking this post for reading as I restore the 520-8 20hp Onan I recently acquired.

Thanks again all. :smile:

[Save Old Iron 1,572]

Glad to be of some assistance. Seems like this particular style of RR unit tends to overcharge when they fail.