Generator

[beatle_bayly]

Hi all,

I've conducted a search of the forums to no avail.

My genny light comes on steady, but only occasionally.

Q1: To check the generator output is it simply a matter of putting a meter across the two connections on top of the generator with the engine running ?

Q2: Will this test help to isolate the regulator as the culprit ?

Q3: I know an alternator requires some sort of back voltage before it will provide output, but is a generator the same ?

Q4: Should I disconnect the regulator before putting a meter across the genny ?

With the light on steady, there does not seem to be any charge going to the battery as it sits steadily just above 12V at idle or at increased RPM.

[Andrew]

Testing the output at the battery will tell you what the whole combo is producing; I'm unsure if you can just test voltage coming out of the generator, but I don't think it's that straightforward.

Andrew

[rogerspeed]

I have a Glenn's ALFA manual reprint, they are available from the usual sources, there is a very detailed, full page of small text print that describes the complete charging system test(s) and proceedure (for generator equiped alfa models). I don't have a scanner and it's complicated, depending on the brand of regulator, but let me try to assist. You can test with ammeter, they stress that when you test the generator with the regulator disconected, don't race the engine as with no regualtor in the loop you can burn out the generator also if the generator is being replaced/repaired because of no output, the regulator should be replaced, because generators generally fail because of faulty regulaors. They recommend that you slightly discharge the battery before trying any tests, (crank with the coil wire disconnetced). Then start the car and do the charging test, keeping in mind that the charging rate should decrease. Anyway the manual is Brookland reissue. Great stuff for the older cars.
1) test battery
2a) test generator output > low output >repeat test with ground jumper; output now ok. clean and tighten connection and or replace ground cable; OR output less than normal> perform elctrical tests on generator repair or replace parts as required
2b) test regulator > regulator not ok > adjust, repair or replace faulty unit
2c) test external resistence circut > resistance normal> battery run down from excessive or unusual drain; OR resistence excessive > clean and tighten or replace cables or regulator

[Alfacliff]

the generator and alternator both need the battery for excitation, the regulator sets how much of the battery current goes in to the thing to control the output.
the easiset test for either is to test the battery voltage at idle, run up the speed and the voltage should increase, but not over 15 volts or so.
cliff

[beatle_bayly]

Thanks all,

As it happens, I have a copy of the Glenns book. Now where did I put it ? Light is now on constantly when running.

After driving around it seems that the genny must be providing a charge. Seems to be around the 12VDC mark which is probably a little low, but the battery isn't going flat after a few starts and the headlights don't seem to drop the voltage significantly. Mind you there is only about 0.2VDC change from idle to 1000rpm.

The light is not staying on when the ignition is off which is good, so I just need to troubleshoot the light staying lit when running.