View Full Version : I need help with generator testing!

08-07-2000, 10:15 PM
That little red generator light is on, and I've been trying hard to figure it out.

My 1968 Chevy sportvan 250 with DELCOTRON 5.5" generator:

Is there any easy way to measure the generator's output? The shop manual offers a crazy setup that requires a load tester and such - I put my voltmeter from the generator's BATT terminal to a ground on the chassis - it read 11.90 - or should i read current instead?? The voltage directly across the battery was 11.94, also while running. When the car is off, across the battery is 12.04

Should the generator be grounded anywhere? There's a wire that goes I suppose to the battery, and the 'F-R terminal connector' with two wires that goes to the relay, but nothing from the ground post (or is that even a ground post??)

Is it a good idea to raise that relay voltage? Is that a possible cause?

Really appreciate your help, thanks,


08-07-2000, 10:49 PM
if your voltage regulator and alternator are working correctly you should read about 13.5 volts reading across the battery terminals with the engine running.red to plus black lead of meter to neg terminal of battery.be sure to clean your connections at both the battery as well as at the alternator and pull check terminals at the above items.outside of that you most likely have a defective part battery,alternator-voltage regulator.your local auto parts store should have equipment on hand to check them and tell you which is bad.but first eliminate connections.good luck .

08-07-2000, 11:15 PM
this is to answer your questions on the wiring at the generator.i,m looking at my 1967 van diagram but it should be the same the b terminal is your main battery,your r terminal goes to position 2 on your voltage regulator,your f terminal goes to position f on voltage regulator,and your b terminal goes to both the left hand fwd headlamp and to a sheetmetal gnd.this gnd point is the same one the voltage regulator also shows it uses.to answer your question the 18 gage wire of the two on the g terminal of your alternator goes to gnd so check this with an ohmeter to ensure you do infact have a good gnd present.bottom line check and clean your connections.good luck hope i helped.

08-07-2000, 11:24 PM
i goofed i should have said the "g" terminal the one with two wires going to the alternator has one wire going to the fwd lh headlamp its the 18 gauge black wire and the 12 gage black wire goes to a sheetmetal gnd.off the voltage regulator you should have an 18 gage black wire "chasis gnd that also goes to the same sheetmetal gnd.hope this clears things up for you.

08-08-2000, 12:56 PM
thanks tom - that's given me some good ideas, and hopefully it is just related to a dirty connection or poor conncetion or such. worked on her hard yesterday, and did manage to fix headlights, fans, horn, and that somehow took care of a major short - so i'll give her again today, will let you know - thanks again for your help! andrew

08-08-2000, 07:21 PM
i'm still wondering about a way to measure the generator's output directly (ie. voltmeter/ammeter directly on the generator somewhere) - any thoughts?

08-10-2000, 06:32 PM
problem solved - replaced the regulator on a friend's suggestion, sure enough - the gen light went out, and the battery is charging just fine - thanks - over and out, andrew

08-10-2000, 10:04 PM
an ammeter would conect in series with the output of the gen.- i.e. disconnect batt terminal and hook ammeter from batt term to wire- a stock 67 generator will probably only put out28 or 37 amps- at 2500 rpm's. the rated output should be stamped on the top of the gen, behind the mouting ear.