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RayS

7790 Voltage Regulator

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RayS










I was using the diesel today with the revitalizer. When done I got off to go sow grass seed. When I came back a half hour later I heard the 20 amp breaker clicking off and on. The key was off and some how it was still getting current through the voltage regulator. I assume it is a internal short in the regulator. The first picture is what was dripping on the ground from the regulator. The Lombardini regulator has 5 pins on it. I am not sure but will look up and see if this is 15 amps or 20 amps. My question is I have a 20 amp Honda voltage regulator. Can I use this? I know the Lombardini regulator is going to be very expensive and would rather use this if I can. If the stator only puts out 15 amps it shouldn`t hurt the 20 amp Honda regulator. Another questions is the wiring? I have a Honda diagram somewhere.

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RayS
The parts book says it is a 12v -12a 3 wire voltage alternator under the flywheel. The part number for the Lombardini voltage reg. is 7362.228. it states it is 12V 14/21A-6 contacts for alternator 3 wires. Thought I only see 5 wires but will look again. Parts book say 6 contacts. So I am thinking after I figure out the terminals on the Honda voltage reg. I should beable to use it. Any thoughts?

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RayS
These people want $268.00 for the regulator. That isn`t happening. I can get a Kohler reg. for $25 or less. http://www.m-and-d.com/results_sql.html?mv_session_id=FAfhE8W3&ml=25&mv_min_string=3&stuff=7362228&x=43&y=11

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midnightpumpkin
Ray, Try to figure out which leads are coming from the stator. The stator resistance should be 2 - 4 ohms. Once you identify the stator leads, measure the AC voltage with the engine running. If it is in the range of 24 to 55 volts dependent on engine speed, you should be able to use the common Kohler 3 terminal regulator. Just remember the Kohler regulator case has to be grounded. If the stator is really a 3 wire stator, like the Onan CCKB, I don't know what to tell you???? Al did a nice writeup on the Onan 3 wire system, but again big $ to replace the rectifier/regulator. John U

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RayS
Looks like the two yellow wires from the alternator will hook to the two (GR) gray wires on the Honda regulator. On the reg. it looks like BL/Y (Black with yellow stripe) will tie into W (white) then that would hook to the (B+) orange wire on the harness. Evidently the (BL) black wire from the reg. would hook to ground even though it is already ground to the engine since it is bolted to the engine. The Lombardini reg. doesn`t appear to have a ground wire. Not sure what the (I) terminal on the 7790 diagram means? It has a brown wire hooked to the C terminal. The (W/Bu) white wire with blue stripe on honda reg. went to generator light.

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midnightpumpkin
Ray, Only a guess but the I terminal on the keyswith is probably Ignition and the C terminal on the regulator is probably a Control input to enable the regulator when the key is on. The Toyota alternator I am putting on Ugly Betty requires such a connection to enable the alternator to output current. I have no input on the Honda regulator, but looking at the 7790 diagram, I would sure give a standare 3 terminal Kohler regulator a shot. John U

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powerking_one
Ray, What are the output spec's of the charging system in terms of amps? Almost all small engine's charging systems using a regulator/rectifier module limit the current by shunting/dumping the excess power from the AC stator coils to ground (waste of power granted). That being said, any 2-terminal AC input (20-40V range) reg/rectifier module which is rated for the max output current range should work. Case in point if were to you take say a 20amp Kohler stator reg/rectifier system and replace it with a 15amp rated reg/rectifier, the rectifier/regulator module would fail in short order trying to dump the excess power to ground. If the output spec's for the charging system are 16amps or less, then consider B&S PN 691185/797375 reg/regulators out there on ePay which are rated up to this. I have picked up a few over the years in the $10-$20 range. Tom (PK)

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RayS
Just checked volts at the stator - alternator wires with engine at wide open throttle. I get 73 volts with meter set on AC and each probe on a stator wire. Is this to high or is it ok? Or would you just divide that by 2:D. Seriously I don`t know.








Here is a picture of the terminal markings on regulator. The two yellow wires coming from the alternator harness are hooked to the two alternating current terminals on the regulator. There is a red wire in the stator harness as well. not sure what the red wire is? Grond for stator maybe? The red wire was not hooked to a terminal on the regulator but since there is a terminal marked L.E. on regulator, I assume it goes there. What does L.E. mean? The orange wire from the key switch or tractor harness goes to the + terminal on the regulator. The brown wire on the end is on that terminal with a slanted line with a dot on it. Not sure what that symbol means. Any ideas? That is a C terminal in the 7790 diagram. According to the first diagram or picture above this system is either 12A or 16A charging system. My Honda reg. is for 20A. Below is a link to a Kohler full wave reg. / rectifier (it is the last one in the link part number KOH24755144S). Would it handle the 73 volts that I am getting from the stator? Thanks for the help and I hope I do not have everybody burned out like regulator:D. http://www.psep.biz/store/kohler_voltage_regulator.htm

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RayS
Just did continuity test from each yellow wire to the red wire. These are the wires coming from the stator harness. The volts on each are .003 and ohms is 1.0 Bob, I checked as you stated. I get 46 volts on one yellow wire and 28.8 to 29 volts on the other. That is with one test lead to ground the other to the stator wire at wide open throttle. Is that to much of a difference?

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BLT
quote:
Originally posted by RayS
Just did continuity test from each yellow wire to the red wire. These are the wires coming from the stator harness. The volts on each are .003 and ohms is 1.0 Bob, I checked as you stated. I get 46 volts on one red wire and 28.8 to 29 volts on the other. That is with one test lead to ground the other to the stator wire at wide open throttle. Is that to much of a difference?
Is that reading on the AC portion of meter?

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CarlH
I have a 7790 that PO replaced the Lombardini regulator with a Kohler 15A regulator. SEEMS to work OK. When I first saw it, I was concerned it wouldn't handle the Lombardini's alternator output. Why I don't recall at the moment. Kohler regulator hookup is straight forward. The 2 wires from the Lombardini alternator stator go to the 2 AC inputs on the Kohler regulator and the Kohler regulator output goes to the battery on the tractor. The other 2 wires for Lombardini regulator are irrelevant for the Kohler regulator. IIRC, the AC outputs from the Lombardini alternator are the 2 yellow wires and the orange wire is the regulator output to the battery. I prefer the Kohler 25A regulator since it has a full wave rectifier and additional current capacity. As Tom notes above, if you are pulling 20+ amps continuously from a 15 amp regulator, smoke will escape. Kohler 25A regulator pn's: 25 403 01 regulator, 25 amp 25 403 04 regulator, 25 amp 25 403 05 regulator, 25 amp 25 403 08 regulator 25 403 20 regulator 25 403 21 regulator, 25 amp 24 755 23 regulator, 25 amp 24 755 98 regulator, 25 amp 24 755 144 regulator, 25 amp

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CarlH
Check the alternator output across the AC outputs, not to ground. The AC referenced to ground could be about anything depending on the regulator design. 46 or 29 volts AC seem VERY high. I don't see any reason for that high AC output from the alternator stator alone. Might be from internal short in the Lombardini regulator. Check alternator output with regulator disconnected. I will check the Lombardini alternator output specified when I get home. There isn't too much to fail in the alternator stator since it is a passive device (an inductor in AC terms or resistor at DC). If it is shorted to ground or internally, there will be no output AC. Likewise, if it is open across the AC wires, no AC output.

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RayS
Carl, when I checked and got 73 volts. I checked it wrong. I get 46 volts on one yellow (stator wire) wire and 28.8 to 29 volts on the other to engine ground. I just went out and checked each yellow wire to the red wire on the meter. These 3 wires are coming from the stator and are in their own harness. One yellow to red is 37.1 volts the other is 37.3 volts.

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RayS


As of now I have the honda voltage regulator on it. It is a 20 amp regulator. At wide open throttle I have 16.05 peak volts at the battery terminal (seems to stay there) and 11 - 12 amps on the ammeter. The ammeter was going back down to zero before I cut out the previous owners shotty wiring connections. Once I put new wire connectors on it was staying at 11 - 12 amps for the 20 minutes I let it run. You would think that the volts (at battery) would start coming down after it peaks to a certain point then start all over again. Out of time and have to go to work. Any thoughts? I will look at it more tomorrow. The two gray wires on the Honda regulator are the stator wires. So I hooked the two yellow wires coming from the stator on the diesel to the terminals that the gray wires are on. The white wire on the honda reg. goes to battery. So I hooked the orange wire which is B+ wire on tractor harness and was hooked to the old regulator. Black wire terminal on honda reg. goes to ground. So I hooked the red wire from stator to that. Still trying to figure out what the c terminal on old voltage reg that brown wire was hooked to does or goes to. I believe it was low oil pressure warning light and oil pressure switch. Have to see if they need a 12V constant source and one of the two I have left should cover that. I have two terminals on the honda regulator left. One is fuel shut off solinoid (should always be 12 volts there) and generator light for GX620. I also added a black wire to the mounting screw of the voltage reg. and connected the other end to the engine ground strap at the frame.

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midnightpumpkin
Ray, When you measure 16.05 volts at the battery was your voltmeter set to read AC or DC volts. It needs to be DC. 16.05 volts will boil the battery dry. I am also curious, is the Honda regulator running hot when you let it run for a while? John U

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CarlH
Alternator output (disconnected from the regulator): @2200 RPM -- 28-30 volts AC @2600 RPM -- 32-36 volts AC @3000 RPM -- 38-42 volts AC appears to be rated at 16 amps DC I noticed in the Lombardini shop manual: - one or both yellow leads grounded demagnetizes alternator - that a disconnected battery ground could cause 'regulator burning' - an 'interrupted' green lead could cause regulator to charge at maximum rate (=> battery boiling) - grounded green lead => battery short circuit (this manual is obviously a poor English translation from the Italian original ;))

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HubbardRA
Use the two AC wires into either the Honda or Kohler regulator, then wire the other wires from the regulator according to a diagram for that regulator. It will work. I once had a Kohler, but no regulator. I just got a 25 amp bridge rectifier, which hooks to the two AC wires and gives DC+ and DC- on the two other wires. I wired the two positive and negative DC wires to a regulator from a Starter-generator. It worked great and I ran it for several years before trading that engine off.

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powerking_one
Ray, With this Honda regulator installed and showing +11 amps charging and the battery voltage being ~~ 16 volts, I'd be concerned that the stator voltage output is driving this reg/rect module into an unregulated "state". In a typical AC stator rect/regulator system; it limits the current to maintain a 13.8 to 14.somthing voltage range at the battery. So, the battery could be bad with a shorted resistance cell; or the Lombardini stator voltage output is too high and the Honda reg/rect just can't operate per spec thereof. With the battery in a no load/drain state, the URL below tells you the relative charge % state of a 12V battery. Measuring 72V A.C. accross the the 2 yellow stator wire sounds way to much for a "typical" U.S." small engine designed system which Tecumseh, Briggs, Kohler, Wisconsin all followed and standardized over the years (AC stator ouput in the 20-40V range). To subsitute one of these reg/rect modules on this engine just may not be an option. I'd be curious to hear more of CarlH's success experience with subsituting one of those 25Amp Kohler reg/rect modules on a 7790. Those whacky Italian design engineers; yeah and what are they doing with the RED wire coming off the stator coils? Maybe a center tap to ground? http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf Tom (PK)

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midnightpumpkin
quote:
Originally posted by powerking_one
Ray, Those whacky Italian design engineers; yeah and what are they doing with the RED wire coming off the stator coils? Maybe a center tap to ground? Tom (PK)
I think Tom hit the nail on the head. The RED wire coming from the stator is most likely a center tap. That way they only needed two diodes to make a full wave bridge. Ray reported 37 volts AC from the red wire to either of the yellow wires, that's a center tapped stator for sure. Carl's stator and regulator are a two wire system, much like we are used to seeing on a Kohler and the Kohler regulator will work. I have suggested that Ray connect his Honda regulator between the red and one of the yellow wires and leave the other yellow wire open. If this works and I'm pretty sure it will, he will end up with a 6 amp charging system instead of the original 12 amp system. 6 amps is more than enough to keep the battery charged, he has no electric clutch and no ignition drain with the diesel. We will be waiting to hear Ray's report back on this. John U

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CarlH
I did not install the 15A Kohler regulator on that 7790. It was installed by the PO. I questioned it. According to the service manual, the voltages v RPM I posted above were across the yellow leads from the stator. You can't see it well in Ray's picture but in the service manual the red wire is connected to the 'R' terminal on the Lombardini regulator and that is connected to the battery positive. I don't have a ready explanation but I wonder if some excitation voltage is needed through another winding in the stator? There are 2 different stators (and wirings) illustrated in the service manual. One is 2 yellow wires, one also has the red wire you are talking about. Lots of questions here and the manual isn't very clear. Note that the Simplicity 7790 wiring diagram only shows the 2 yellow wires from the stator. I will check my other 7790's to see how many wires come from the stator.

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