Need Voltage Regulator Tested

[RobinHood]

The battery on the lawn mower keeps discharging. It starts with a boost. Investigated and found no output (0.9VDC) from the regulator. Input is ~18VAC at idle increasing to ~ 30VAC at 75% rpm.

Did a search and found that there are lots of regulators for sale from $16 to $80. Reviews show that there are also a lot of DOAs right out of the box or within 1-2months.

Decided to “splurge” and get a genuine Briggs&Stratton one. Installed it, no output.

Vendor tells me to buy a new one. If that one works, then I can go through their Warranty Claim procedure to get the money back for the faulty one ( and hopefully get my $s back).

I would like to test the new one (and the old one for that matter) to check if my analysis is correct.

Does anyone in the Calgary area have an AC Power Supply (I think they are called Variac?) with an output of at least 30 VAC that we could hook the regulators to to check for operation? I only have a DC power supply.

Is/are there other ways to test a VR?

Any advice would be appreciated. Thanks!

Old VR is on the left, new one on the right. Yellow wire pair is the AC input, single red is DC + output. The case is ground. All contacts are clean.


Wiring/Parts diagram

 

[DavidR8]

I wonder if your 'local' CDN Tire could test it or maybe a friendly garage?

 

[RobinHood]

Good idea, David. There is an alternator rebuild shop not too far from me, I should swing by and see if they test VRs. They have a sign saying “ Free Alternator Test”.

 

[DavidR8]

Alternator, regulator, potato, potatoe

 

[Johnwa]

If that fails I do have a variac.

 

[RobinHood]

So I called the alternator shop - they basically only deal in automotive equipment. Understandable.

I don’t have the Technical manual for the lawn mower and thus can’t confirm the values I have found. Apparently in a 16A charging system, the output voltage from the stator/alternator is >30VAC at full power - I get 35VAC @ 100% rpm and 30VAC @ 75%, dropping off to 19VAC @ idle rpm.

Update:
Our heating system has 24vac control circuitry. The transformers put out 30VAC. So I hooked up the input side of the VRs to one of them. Both the original and the new VR have 0.5VDC on the output side - so I think that they are both hooped.

Am I missing something?

@Johnwa , I think I will take you up on your offer. Can you please PM me with your availability and details. Thanks.

 

[combustable herbage]

I would agree you have come up unfortunate with the new one. I would also check with an ohm meter with no battery hooked from the positive lead to ground and make sure there is nothing dragging that line down causing the regulator to blow. I checked my john deere and it was around 14mega ohms so it should be somewhere in that range.

 

[ShawnR]

When you get it working, you could fuse that DC line. It might be trial and error at first, to find the right value, unless you can find the current rating of the coil in the motor but at least if something happens ie battery cell shorts, causing excessive charge rate, the fuse might save you buying another regulator. I had some Kohler engines years ago, still have one on my digger, and everyone of them needed a new regulator. Hate those things! But all were replaced with ebay cheapies and the only engine I still have is still using the same regulator. But since you are in a warranty situation, hopefully the replacement works. iirc, my ebay supplier had to send me a replacement too....yep, they can be crap fresh out of the pack

 

[PeterT]

Late to the conversation. When you measured your regulator output, was it hooked up battery? Are you sure your battery is not defective & wont hold a charge? If the regulator is delivering correct voltage/current but the battery chemistry is pooched you typically see OK looking nominal voltage but issue is the voltage suppression under load & curve over time. Typically when batteries going south they build higher IR right up close to internal short if real bad. So the same input charging power isn't as effective to charge it. Then potentially the battery drains to lower voltage state which is bad for it & its a vicious circle. I have a 12v universal battery charger that senses/conditions. Also open jaw type clamp meter to see DC current if that's of value. The auto guys have battery load testing apparatus that basically snapshot voltage decay & this indicates health but I'm not sure if they extend to smaller cells.

 

[ShawnR]

Late to the conversation. When you measured your regulator output, was it hooked up battery? Are you sure your battery is not defective & wont hold a charge? If the regulator is delivering correct voltage/current but the battery chemistry is pooched you typically see OK looking nominal voltage but issue is the voltage suppression under load & curve over time. Typically when batteries going south they build higher IR right up close to internal short if real bad. So the same input charging power isn't as effective to charge it. Then potentially the battery drains to lower voltage state which is bad for it & its a vicious circle. I have a 12v universal battery charger that senses/conditions. Also open jaw type clamp meter to see DC current if that's of value. The auto guys have battery load testing apparatus that basically snapshot voltage decay & this indicates health but I'm not sure if they extend to smaller cells.

Yes to what @PeterT says. Just measuring the voltage output, with no battery connected, might not give a true indication. You could charge the battery with a separate charger, measure the voltage when it is mounted in the machine, then start it and see if the battery voltage climbs, stays, or drops. Ideally, put an ammeter in the circuit to see if there is charging current too.

 

[RobinHood]

I would also check with an ohm meter with no battery hooked from the positive lead to ground and make sure there is nothing dragging that line down causing the regulator to blow.

On both the old and new VR, there is an open circuit to ground from the positive output.

When you get it working, you could fuse that DC line.

There is a 20A fuse in the circuit. As far as I can tell the LA140 has a 16A charging system.
When I tested the output of the VR, it was not connected to anything - just mounted to have a ground.

The battery was brand new last year. It holds a charge. I charge it after mowing with a “smart charger” (an older model, but it works well).

I use a FLUKE DVOM. It can measure current with the clamp jaws. There is 0 coming out of the VR.

Just measuring the voltage output, with no battery connected, might not give a true indication. You could charge the battery with a separate charger, measure the voltage when it is mounted in the machine, then start it and see if the battery voltage climbs, stays, or drops.

So you are suggesting that the VR has built-in voltage sensing circuitry? Unless there is a minimum voltage on the output lead, it may not even trigger the charging circuitry?

I will have to go check that. The battery is currently fully charged and reads 12.5V. I’ll connect the new VR and see if it bumps the output voltage to somewhere around 13.5V - 14.2V.

I’ll get back to you on that....

 

[PeterT]

Longshot but was the new battery the same class or very similar? (chemistry, nominal voltage, Amp-hr capacity)? Reason I ask is I wonder if the regulator unit is more than a regulator & has some on-board smarts that is sensing battery voltage conditions & now being tricked by what it perceives as a depleted or full. Programmable chargers work like this. You select chemistry & other parameters... based on that it invokes a program that delivers the voltage & current in a prescribed manner. But choosing the wrong parameters confuses it. Maybe that's why your charger can charge it but it gets messed up with reg?

 

[RobinHood]

So you are suggesting that the VR has built-in voltage sensing circuitry? Unless there is a minimum voltage on the output lead, it may not even trigger the charging circuitry?

Yes, it does have built-in smarts! The new VR works! 14.0VDC, 5.0A charge (measured on the AC side, as my clamp-on is for AC amps only).

For laughs and giggles I installed the old VR: it is outputting 18VDC! Probably cocked my old battery. It was 12 years old by the time it died, so maybe I should not complain.

The new VR is back in the mower now.

A huge thanks to everyone that helped me solve this problem! Learned something today. That makes it a really good day. Thanks!

 

[Dabbler]

Many regulators with solid state circuitry need an load to have an output. If you have a 10 - 20 ohm 10 W resistor, that would suffice. Measure the voltage across the resistor.

[edit] sorry we posted at the same time!

 

[ShawnR]

Glad to hear you are up and running!
There are a number of ways to control voltage output. Those simple regulators don't get too complicated internally, but many need a current flow to sense voltage (see @combustable herbage profile pic....) so no battery, no current flow, no output. What @Dabbler says often works but I have chased my butt more than once assuming that and it was not the case. The best bet is to put it into practice and then do some checks.

Cheers,

 

[RobinHood]

Thanks Shawn.

I did learn that by isolating and testing a component by itself is not always the best course of action, especially if that component depends on something downstream for ”feedback”. I though there would need to be some sort of feedback wire for that, but I was wrong again, as the internal electronics can look at the single output wire to determine what the state is.

Lesson learned. Thanks again.

 

[PeterT]

What little experience I've had with regulators, the amp rating is usually a rated maximum, not what its delivering. 12V 5A usually means hold 12V +/- float tolerance at 0-5A depending on the actual draw. And max current may further defined at operating temperature or continuous duty. All I know is the specs are reduced if the smoke escapes LoL.

 

[RobinHood]

Both the old and new VR have no specs written on them/included with the packaging. That made troubleshooting so much more challenging. So I made some assumptions based on my understanding of VRs (some of which turned out to be wrong as I found out with the help of this forum) and went to town.
I was really trying to avoid taking the machine in to the dealer - like they kept suggesting when I pressed them for info regarding the VR. For sure would have cost a bunch of $s with their shop rate at $125/h and a min diagnostic fee of $150...
So really happy that it works.

 

[combustable herbage]

I think a 12 volt incandescent bulb might have worked as well.

Many regulators with solid state circuitry need an load to have an output. If you have a 10 - 20 ohm 10 W resistor, that would suffice. Measure the voltage across the resistor.

[edit] sorry we posted at the same time!