• If you like antique engines, vintage tractors or old iron, please register and join us. When registering, please provide your CITY and STATE as your location!

Dayton Generac 8kw standby with no power

phabib

Registered
I recently bought a Dayton branded standby generator that I'm pretty sure is a Generac. There is a Generac sticker under the lid of the control board. It is 8kw and uses a two cylinder engine with a belt drive. It was made in 1993. Dayton's number is 5W960.

The engine starts right up but I only get 10V out of the output terminals. It is AC at 61Hz.

This was measured with nothing else connected to the generator.

I have the instruction and parts manual, but no shop manual.

Every few seconds, I hear a buzz/zap/arcing sound for a second or two.

So far I have checked that the circuit breaker, CB2 in the schematic, is not open. This is a breaker across what they call the DPE winding. I also measured across the field winding and I get about 15 Ohms.

Is there a systematic list of things to go down and check and what are my options for repairing this?

Thank you.
 

K D Redd

In Memory Of
On a Generac generater, the DPE winding powers the voltage regulator. The one I worked on, a 20KW unit had a thermal breaker in the DPE winding so if the stator got to hot the generater would stop generating. It also had a wire that would by pass the thermal breaker if the breaker became a permanently open. I can see a breaker in series between the DPE winding and the regulator but I can not see a breaker across the DPE winding as this would be the same as a short across the DPE winding until the breaker opened. If the breaker was to large, this could cause the DPE winding to overheat and burn out.

Kent
 

phabib

Registered
The breaker is in series with the DPE winding as you said. Across was not a good word for me to use.
 

phabib

Registered
I found the repair manual online and started the diagnostic process.

I found that the stator DPE winding has 1.6 Ohms of resistance instead of the 1.1 the shop manual says it should. That doesn't seem horrible.

Next I tested the resistance between wire 2 of the DPE and one of the long bolts on the stator can. Instead of infinite resistance, I got 6.7M Ohm.

The resistance between wire 2 of the DPE and each leg of the output winding at wire 11, and 44 was infinite, as expected.

Resistance between wire 2 and wire 66 of the battery charger winding was also 6.7M Ohms.

This makes me think the stator is shorted. Am I right? Can the stator be rewound at a motor shop? If not, is the part available at a reasonable price? I'd be fine with a used one if its good.

Is there a whole new generator head in my future, and is there a good one to pop in there?

Thanks for any advice.
 

Fred M.

Registered
Phabib-

6.7 MegOhms is not exactly a short circuit. It might be a sign of moisture that would evaporate after getting up to operating temperature. Or, it could be a sign of a leakage that would develop into a real short circuit over time. Whichever, I don't think that reading is related to your immediate problem.

You might only need to flash the field. If that isn't it, I'd check the rectifier that uses the DPE voltage to produce DC for the field.

Fred
 

phabib

Registered
Thank you for the response.

I couldn't decide if 6.7M was a short or not. We have had some rain recently.

What does it mean to flash the field and where can I learn how its done?
 

phabib

Registered
One more thing, looking through the schematic, the DPE winding goes right into the electronic voltage regulator. There is no outside rectifier that I can see. So maybe the regulator is my problem?
 

K D Redd

In Memory Of
On the 20 KW unit I worked on, yes the wires from the DPE winding go directly to the regulator. When I was first called to look at repairing this generator, after a Generac Service Tech. said it was NOT repairable. The owner, who is VERY electricity challenged, had the 12 volts from the engine starting circuit boot-strapped to the brushes. The generator was outputting one half voltage. I brought the generator to my shop and figured out the wiring. When I had it wired correctly I fired the engine up and IT DID NOT generate. This surprised me as I thought there would have been some residual magnetism from the boot-strapped 12 volts. I flashed the field through the brushes again with 12 volt. When I did this the generator started making voltage. Not full voltage at first. It built to 220 volt over the period of about a minute. This was now three years ago. The generator was used every weekend to power the owners track where Garden Tractor were pulled and Go-Karts and Racing Lawn Mower were raced. They have not contacted me with any further problem with this generator.
Try flashing the field with 12 volt with the engine running. It may start generating. If not reconnect the 12 volt and check the output voltages of the generator. you should see about half voltage. With what little experience I have it seems to me as if most fields are supplied with about 24 volts DC to generate full output. If you get about one half the output voltage and the voltage DOES NOT build, I would say the regulator is bad.

Kent
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
I think your higher than expected resistance reading -could possibly- be due to the resistance of your meter leads.

When I measure low resistances, I first connect the leads together and note the resistance. Then I measure the circuit and subtract the lead resistance from the reading.

Works for me.:)

Take care - Elden :wave:
http://www.oldengine.org/members/durand

I found the repair manual online and started the diagnostic process.

I found that the stator DPE winding has 1.6 Ohms of resistance instead of the 1.1 the shop manual says it should. That doesn't seem horrible.

....................snip.......................
 

phabib

Registered
The meter lead resistance is why I wasn't too concerned about the low resistance reading. I usually figure that's good for about 0.3 Ohms, and since there is some corrosion on the things I was measuring to add more, I was OK with it.

I did a bit of research of this flashing the field and found that everyone seems to have a favorite method.

One was to plug a 12V supply at the output of the generator, positive to the hot and negative to the neutral.

One was to plug a reversible electric drill into the generator and to spin it backwards by hand with the reverse switch set for reverse rotation.

Another was to use a 6V lantern battery into the field coil.

It is not clear to me if this should be done with the engine running, or if I'm just trying to do it with the engine off for enough time to build up enough residual magnetism to allow the process to bootstrap after that.

As a total generator novice, I'm not sure about the best way to proceed.

A pointer to definitive method (if there is one) would be a great help.

Thank you to all who have been providing help. I would love to not have this turn into the most expensive $500 generator in the world.
 

Jim Rankin

Registered
Age
58
All those methods work on some generators and for some folks.

Some of them are really easy and safe, so if you want, try those first.

Directly putting DC current through the field can be done both with the generator running or stopped. You need to know the proper polarity of the field. (Match + and - ) and it's safest to disconnect the regulator, though it doesn't always have to be done. Some recommend flashing through a light bulb in one of the leads from the battery. This serves to limit the current and voltage a bit and gives a visual indication of making a circuit through the field or not.

If it is done with the generator stopped, like you said, you are depending on creating enough residual magnetism to get it going once you start the engine.

If flashing with the engine running, you will see if there is a voltage response while you are actually flashing. In general if it won't build voltage while flashing with it running, there's almost certainly something wrong with the field or the armature. With the engine running takes some prior planning and care to do it safely for both the generator and operator.
 

phabib

Registered
I would assume that if I flash it while running and I see some real voltage coming out of it, but I don't see anything when I re-connect the regulator, I must have a bad regulator?
 

Jim Rankin

Registered
Age
58
Yes, You're right, you've pretty well narrowed it down to the regulator and it's power supply (the DPE winding in this case) if the generator will build up good voltage while flashing.

You would like to see voltage in the correct relationships between line to line voltage and line to neutral voltages. (120 and 240 for example you might see 40 and 80, but that would be the correct relationship of 1 to 2) if it's 120 only, you don't have this check. If you flash with something less than full excitation voltage, you get less than rated AC output voltage, but the relationship between line-line and lines-neutral will be true even with only residual voltage, not even flashing. It's just easier to see when it's not a real low voltage.
 

phabib

Registered
Calling out the DPE winding as the power supply input to the regulator was a huge help in my understanding what's going on.

So I did the field flashing with the generator running and the field coil disconnected from the regulator. I had an AC voltmeter connected to one leg of the output.

Original state was 5V per leg.

Running with field disconnected, 5V. I guess this means that the residual magnetism with no power provided generates 5V.

With 12V from the generator battery running through a test light, the voltage went up to 19V.

With a straight wire, the voltage got to 89V.

I reconnected to the regulator and it did 19V for a few seconds, then drifted to back down to the original 5V.

From this I suspect that my regulator is defective. I also suspect that the field voltage is more than 12V max. Maybe 18-24V.

Does it make sense for me to throw a new regulator on it or is there some other regulator test I can perform first to make sure I don't throw money at a part I don't need?

Grainger no longer stocks the voltage regulator for this thing. I have heard of universal voltage regulators. Is there a consensus about which one to get or which one to stay away from? Better yet, is there a source for a used regulator that I could throw in there?

Finally does anyone know what the Generac model number was for my generator? I was able to find the repair manual for it, but after looking at every manual I could find, I never saw an owner's manual for it where I could see the Generac model number to try to find parts that way. My Diagnostic Repair Manual is part number 83045.

Thanks to all of those who've been helping me out on this. I wouldn't have known where to start without the crash course in generator fixing I've gotten in the last few days.

I should have known better than to say finally after that last question. It turns out I have a couple more.

Prior to swapping out the regulator, should I maybe check the voltage output of the DPE winding? It could be that the regulator is fine but the power source for the field is dead meat.

Then, why have a DPE winding in the first place? Why not take some power from the main power winding and use it to feed the field?

Next is I'm thinking a general purpose regulator wouldn't be that big a deal to make with a small microcontroller (Its what I do for a living). You could take the 120V as an input, isolate and rectify it then run it through a PWM to drive the field through a largish FET. Probably about a $15 parts cost. Is this basic method and idea sound?
 

Fred M.

Registered
Phabib-

The key to finding an owner's manual would be determining the Generac model number. See if you have the data plate shown on page 1.2-3 of the manual.

I found the 83045 manual at <http://www.zabatt.com/product_manuals.html>. I see they also have the 81134 manual for the V-Twin engine, if that applies to yours. They have other manuals, if you can figure out which one you need.

One reason the DPE winding might be separate, is to isolate the control circuit from the AC output voltage.

Is Grainger the only source of Generac (or Guardian) parts? I'd check other Generac dealers to see if there are others.

Fred
 

Jim Rankin

Registered
Age
58
If you can 'roll your own' version, you would be ahead of most of us who cannot even repair the OEM models. Replacement regulators are frequently too expensive to justify purchasing for an old generator of unknown condition.

There was a thread on here a few weeks ago about someone who had a bad DPE winding and had already bought a new rectifier or regulator or something that didn't help. Here....
http://www.smokstak.com/forum/showthread.php?t=71241
 

phabib

Registered
I was hoping to find a Generac number in order to see if Generac had the parts. From the 83045 manual that I found online, I can see that this existed in a Generac labeled product as well as being OEM'ed for Dayton, but I've only got Dayton numbers and this is too old for them to stock parts. Maybe Generac still has the regulator or a drop in replacement if I can get a Generac number for my device.

Making a very general purpose regulator seems like a simple enough project, but the subtleties of getting something truly right are never evident the first time you think about it.

I'll poke around the generator and regulator some more when I get home and see what I can find as far as part numbers.
 

phabib

Registered
I wound up buying a Power-Tronics VR50 regulator on Ebay for the generator. It was way cheaper than I could find a Generac replacement. I connected up the 4 wires and after turning the adjustment pot a few turns I'm generating power.

Thanks to all who posted here to help me out.

I learned everything I know about generator repair in the last 2 weeks and most of it was from this group.
 

Raymond

Registered
Age
71
The DPE winding is used to simulate a separate exciter. This way the exciter field power isn't reduced by load application , it's actually increased. Generators excited by stator output (shunt excited) suffer from field foldup with application of loads with current higher than rated. (motors are 6x, incandescent lights are 10x). They simply fall on their butt. This protects the generator but fails to start high current loads. The separate exciter is capable of usually 300% rated current but can cook the stator unless more carefully protected. A heavy incandescent light load appears as a short circuit for several cycles. It's a simple economic consideration. A sturdy unit with proper protection costs over 3 times as much as an economy unit with the same nameplate rating. The difference is that after repeated abuse, a well built unit will cruise through, an economy unit will fail. Very few people know the exact electrical characteristics of the load they attempt to run. To compare the durability one needs to look at the weight of the generator (not the engine) and the price. My rule of thumb is if you pay less than $400 per KW for a generator (new) you are wasting your money. Most used generators have multiple problems and a bargain isn't usually a bargain unles you are an expert. An 1800 rpm diesel is the best value. The most important reasons are that it won't exphyxiate you or rattle your nerves and uses 30 % less fuel.
 
Top