motorrad
My first post to the forum and it's a doozie! I have a 45KW custom Generac unit from the '90's that I'm attempting to get up and running as a backup residential system. The unit has a 45KW brush type head coupled to an industrial Chevy V8 running liquid LP. Good setup with easy mechanicals, etc. Previous owner decided to update the electronics and scrapped all the original Generac stuff replacing with the following: Engine control - Deep Sea electronics DSE703; ATS control - Mcpherson controls CM0900; Automatic voltage regulator - Mcpherson SS053 universal. The Mcpherson controls products ([url]www.mtspowerproducts.com[/url]) are universal type items and I've gotten good customer service from them. Previous owner couldn't get it to work, and so far I've not been able to get this unit functional either after lots of diagnostics and testing.

Here's the lowdown on technical information:

1. The field reads 10 ohms slip ring to slip ring.
2. Using a DVOM (Fluke) the stator is not grounded
3. When I apply 12 volts to the field during operation the generator head outputs around 60 volts on each leg (120 volts combined).
4. I've confirmed that the DSE703 engine controller is properly wired. The engine starts and runs great and all automatic functions work.
5. The SS053 universal AVR is wired correctly according to it's requirements - however will never output anything on the field circuit.
6. I purchased an additional automatic field flasher unit (Mcpherson SS500) and installed. Still cannot get any field output from the AVR.
7. The DPE wires output 80VAC when I manually apply 12 volts to the field when running.
8. The field and the DPE wires show no residual voltage when idle.
9. When tested with a DVOM the DPE wires show 0 ohms resistance across the terminals and do not show to be shorted to ground.

I've attempted to manually flash the field numerous times with no luck. Flashing is done by applying 12 volts across the field leads. The generator head does have the Generac DPE coils and wire - however are disconnected and secured. Not technically necessary with the universal type AVR's.

I've had several discussions with the folks at McPherson controls and they determined that I had a bad AVR. I subsequently replaced that unit and still no luck. Does any of the Generac techs out there know if this unit has any unusual things I should be looking for? I've considered purchasing one of the Generac 67680 regulators and installing, however don't won't to spend any more money parts swapping without some comfort I'm heading the right direction. Does the 67680 use the DPE circuit for field boost?

Thanks for any help you can offer and for reading my lengthy post.
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Skip Douglas SkipD
If you could define the abbreviations you're using, a few of us who don't understand them might be able to help. I think AVR is Automatic Voltage Regulator, but DPE floors me.

It's always a good idea to include definitions of abbreviations in posts on a forum. ;)
Skip Douglas
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motorrad
AVR does in fact stand for "automatic voltage regulator." DPE is an abbreviation commonly used by Generac for a supplemental field exciter coil. Not certain what the abbreviation stands for but I understand that they use it to provide a separate voltage source for the voltage regulator. Point being so that if the normal load side is dragged down by high loads the voltage regulator always has a steady source. That is my interpretation so by no means consider that 100% correct. Note that in my configuration I don't use the DPE because the universal voltage regulators state for it to be wired to the normal load side. For purposes of residential backup that seems fine to me - but looking for someone to help confirm.
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Skip Douglas SkipD
Thanks for that.
Skip Douglas
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mastr
What exactly does it do when you crank it up? Does the auto flashing module work? Do you have residual voltage? The SS053 installation sheet indicates that you can use a separate winding to power the regulator, using what they call the European hook up. While the DPE winding may not be "technically necessary", you have little to lose by trying.
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motorrad
Did a little more work today and still no luck. When the unit cranks with the units connected in either fashion (European style with the DPE circuit, or connected to the normal stator circuit) still cannot get anything to the field. Just to prove that I'm not crazy I applied 12 volts directly to the field from the battery and let it run for about 10 minutes. Voltage out of the generator head holds steady in that configuration at 60 volts on each leg. I also checked the amperage on the field when running this way (no load on the unit) and it showed 1.3 amps. This is well within the spec for the universal voltage regulator. Based on the tests so far I am convinced that the generator head is OK, but for whatever reason the universal regulator is just incompatible.
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motorrad
Anyone have the wiring schematic for the Generac 67680 regulator by chance? I've searched the internet tonight with no luck - lots of diagrams for the 830490 type but none for the larger regulator.
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ohmslaw
The Automatic field flash should be applying dc voltage to the brushes.
The avr should then recognize low voltage and apply a higher voltage to the brushes and vary that to maintain the proper output. What do you get out of the voltage regulator on the field side? I say the voltage regulator is not wired correctly or has failed. The alternator appears to be working properly.
Tim
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ohmslaw
I would use the 5 wire method fo rthe avr. F+/ F- goes to the field the same way you flash the field. What output do you have on the f terminals?
Tim
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motorrad
I would tend to agree that the AVR seems to not function due to failure or being wired incorrectly. I have been over the wiring numerous times at this point and am confident that it is correct (I've actually changed it back and forth from the "standard" setup to the "european" five wire setup a couple of times). This is the second regulator as noted before. This diagnosis was what me and the technicians at McPherson came up with also and that is what prompted me to purchase the second regulator and field flasher. I suppose it's entirely possible that I got a second bad regulator. I hate being a parts swapper. If I go the route of purchasing a third regulator it won't be from McPherson it'll be the original Generac type.
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motorrad
The F+ and F- terminals never output anything when wired correctly in either fashion. The field flasher works fine when not connected to the field and AVR (turns on, applies 12V to the field terminals and times out). When connected into the system however, the F+ terminal doesn't show anything when activated which makes me believe that it is shorted or senses a problem condition and doesn't apply power to protect itself.
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ohmslaw
I would not replace the regulator. I would check the output of the regulator on the F terminals. No output is a problem. Then check input. If you have power in on the sense line and no output on the F terminal i do not see how it could be anything else but the regulator.
Tim
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BNSFtheLeader
I'm really confused, maybe I'm not reading it correctly.

You can start it up but you cannot get power out of the unit even though you have 120v out of the terminals?
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mastr
First, I'll make this disclaimer-I have zero experience with the VR you are using. Some of the other universal regulators I have used will die a quick death if either field lead is grounded even momentarily. Do you have a diagram of your field flashing unit? Could it be grounding a field lead during the flash?
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motorrad
I actually only get 60 volts out of each terminal when I apply 12 volts directly to the field. AVR never outputs anything regardless of what I do. The field flashing unit is an SS500 which you can find on the internet pretty easily on the MTS products site.
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BNSFtheLeader
motorrad;7534 wrote:
I actually only get 60 volts out of each terminal when I apply 12 volts directly to the field. AVR never outputs anything regardless of what I do. The field flashing unit is an SS500 which you can find on the internet pretty easily on the MTS products site.


Did you disconnect all the Stator leads and perform the Stator test to make sure it's not burnt?
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bronco
New thought. As I looked at the regulator online I see that it needs a min. of 100 vac to turn on. I would check the T8 & T9 output to the VR (generac uses S instead of T) with flash and if your not getting 100 VAC you might need a lower voltage regulator.
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BNSFtheLeader
It sounds like the Rotor is shot. I just replaced one going back about 3 months ago and the terminals had an output that was much lower than 120VAC (Not sure off hand), I wish I had took pictures of it.

When I took it out the winding on the rotor had an area that was burnt out and the Stator was burnt in several places so the whole atl was replaced.
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motorrad
Got the unit going today. I installed one of the Generac voltage regulators using the DPE circuit and away she went. Apparently the universal voltage regulators were undersized for this unit. I did end up using the SS500 field flasher to provide "field boost" as noted in the Generac manual. Works great. Thanks all for your posts and help.
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