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Guzzi 1000 SP voltage issue

V

ville koskela

Just got it firing!
Joined
May 27, 2015
Messages
10
Location
finland
Hello. My 1000 SP 1980 provides little too much voltage. These are measured on a running motor with digital voltage meter from battery.

1000 revs 13-14V
2000 revs 15V
3000 revs 16V
4000 revs 18-19V

Ground connections are checked, so is alternator. Should I suspect regulator or rectifier?

br koskela
 
Regulator. Regulator controls the field strength of the rotor. Good electronic replacements are available.
 
I changed the regulator. Still measured the same voltage. What would you suggest next?

The problem at first was quickly emptying battery. Battery is less than a year old.

Koskela
 
What is your voltmeter reading on a charged 12 volt battery? That is test on another vehicle.
 
Some of these voltages are a tad high for a 12V battery - indicating an overcharge situation, which will shorten the life of the battery and possibly blow some globes. Everything points to the regulator, even though it's been changed, a 2nd opinion (or a borrowed one) might assist here. A long shot (I might be talking out my arse here though) is the alternator itself.
 
ville koskela said:
Fully charged battery gives 12,7V
Click to expand...


Sounds like the voltmeter is reading correctly. With a diode board, it either works, or you get no rectification of the AC voltages off the alternator, or one of the three lines off the alternator won't rectify so you get low voltage. I've never run into this situation. Check the wiring to the regulator. Something is causing the rotor to get full current for max output. A schematic for your bike is available in the resource section. One of the tests for the Bosch system is to jumper the connector for the regulator to see if the system will charge, In your case, the regulator isn't turning off the rotor. Somehow the rotor is getting constant current and it shouldn't be. Has to be a wiring issue in my opinion.
 
The ignition switch was full of green sludge. I cleaned it. Now there seems to be a lost of connection as it won't start. Probably sludge was connecting the pins.
 

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Use this schematic. https://www.guzzitech.com/forums/resources/1980_1000_sp_nt.108/ Remove the regulator (item 35). Place a volt meter lead (+) on the purple wire connection that goes to the regulator and a lead (-) to ground. Turn on the key. Do you read 12 volts? If you do, that is the problem. If you have zero volts, lift the brushes from the rotor. Take an ohm reading of the rotor through the two slip rings. Should be 6.9 +/- 10%. To check the stator, remove the connector to the diode board. Resistance between each pair should be 0.62 ohms. If all these check are good, then it is possible the replacement regulator is defective.
 
Thanks. Voltage between ground and df on regulator connector is zero with the power on, motor not running. Between d+ and ground 12 V which is 0,5V lower than battery voltage. Resistance through rotor is 5 ohms and through all stator coils 0,8 ohms.

I wonder if it is possible that I have burned the new regulator during testing.
 
Last edited:
ville koskela said:
I wonder if it is possible that I have burned the new regulator during testing.
Click to expand...

That is possible. Use a jumper on the regulator connector to provide a constant 12 volts to the rotor. If your output readings are the same, then I'd say you have another defective regulator.

Your ohm readings for the rotor and stator are a bit off, but then the components are possibly 35 years old and the specified readings are for new, or near new components. You've had a few heat cycles that could change the values.
 
Now it works. I replaced the battery, cleaned the ignition switch and regulator connectors.

Btw, where is the relay for flash/horn located on the bike?
 
There is no relay for the horn. There are only two relays on the bike. One for the starter solenoid, and the other for the high beam flash. So find the two relays, the one for the starter is easy to identify, it should be under the side cover. I think the high beam flash is under the fuel tank, but I haven't been in a SP for a very long time.
 
I think high beam flash and horn are operated from the same switch and activate both at the same time. There is something nearby the regulator under the tank, that is probably the relay I am looking for.
 
Looking at the schematic, the switch either provides a ground to the horn circuit or the high beam flash relay. It can't connect to both at the same time. You toggle one way for horn, the other for flash. Later models have a separate switch for the high beam flash.
 
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