Generator Dash Light

[Damon]

My generator dash light stays on.  I placed a meter on the alternator and see a rise in voltage from idle 12.66 to 3000rpms or so 13.4.  What else could it be?

Thanks

[Sauron327]

Check the connections on the VR. And all others too. Horn relay bussbar, junction block behind battery, and especially the grounds. I assume you are using a stock VR and do not want to use a Wells VR715? You should be charging at least 14 volts with no accessories at the back of the alternator. I'm not an electrical magician but I'd start there before you start seeing how the GEN light is fed; which I believe is the brown wire from the VR.

[Damon]

Thanks Sauron327

I am putting this car back together (long story) so that could be it. Where is the VR and horn relay bussbar located?  What should be plugged int the junctin block?  My car currently has nothing.  The pos cable (new) and a separate smaller wire along with the battery cable.  Dont know what  Wells VR is, I may have that as its new. 

Thanks again

[Sauron327]

Voltage regulator is on the left side of the rad support and should be grounded, horn relay next to it. Junction block behind battery is main feed to system from battery. I'm a tad confused because you said the car currently has nothing but you are testing the charging system? Is this the H. Orange car you are restoring? A Wells 715 is an electronic voltage regulator. Not origional looking unlesss you change the covers. But you can tell by looking at the back of the housing, Judges know the difference. I don't know what your intentions are with the car.

[Damon]

Voltage Reg is a new Delco Remy.  It appears to be grounded.  All terminals filled on VR and Horn Buss below it. 

My junction block (new) has nothing mounted to it. I believe the wire that should have gone there is mounted directly to an auxillary feed on the pos battery terminal.  I am wondering how many wires the junction block should have?  Everything seems to work fine, car starts, runs, horn works, all exterior lights, radio, etc.  The only issue is my "Gen" light stays on.

I can take the wire now connected directly to the pos battery terminal and run it to the junction block and then to the pos battery termibal but I dont see how that will solved my problem.  I have a multi meter, what else can I check?

Thanks,

Damon

[Sauron327]

Is this a new harness? I'm not sure how the system is being fed if there is no wire going from the battery to the junction block and from there to the VR and horn relay. Where does the large red wire go that comes from the harness at the VR? It has to go across the radiator support to the j.block. Your also not putting out enough voltage. 13.4 is not enough. Test the alternator. New Delco Remy VR does not mean it's good. Your system is sensing inadequate output. My gen light was on and I was only putting out 13.1 volts at the back of the alternator and I switched to a wells VR715 and problem solved. This may not be your problem. If voltage testing is required on the wires at the VR then you will have to do as I and research it. For I cannot rattle that info off the top of my head. 

If someone else with electrical diagnosis expertise can add please do so.  

[Sauron327]

While engine is running what's the voltage at the back of the alternator and at the battery?

[Damon]

Is this a new harness? ANSWER: No

I'm not sure how the system is being fed if there is no wire going from the battery to the junction block and from there to the VR and horn relay. ANSWER: Because and I am guessing here, the wire that should have went to the junction block was connected directly to the new positive battery terminal.

Where does the large red wire go that comes from the harness at the VR? ANSWER: DIrectly to the positive battery terminal, will verify tonight after work.
It has to go across the radiator support to the j.block. ANSWER: Thanks, will check.
Your also not putting out enough voltage. 13.4 is not enough. ANSWER: At what RPM should I check for voltage?  Did mine from idle to maybe 3,000rpms at most.  It did climb as the RPMS rose.  I checked the back of the alternator and at the battery, both read the same.

Test the alternator. ANSWER: How?

New Delco Remy VR does not mean it's good. Your system is sensing inadequate output. My gen light was on and I was only putting out 13.1 volts at the back of the alternator and I switched to a wells VR715 and problem solved. This may not be your problem. If voltage testing is required on the wires at the VR then you will have to do as I and research it. For I cannot rattle that info off the top of my head. ANSWER: Good info to know..

If someone else with electrical diagnosis expertise can add please do so.   
 
While engine is running what's the voltage at the back of the alternator and at the battery? ANSWER, 12.66 at idle and rose with RPM's to 13.44 at about 3,000 or less.
 
 

[Sauron327]

My car will put out 12.7 volts at idle, which is fine for a 37 amp alt. And it will hit 14.2 before  I get to 2 grand. Your car is still not reaching optimum output. You say it's an old harness so inspect and CLEAN all the connections and insure all EXCELLENT grounds.  Before you start checking proper readings at the brown and blue wire at the VR I would have the alternator tested and put in a Wells VR715. The readings of those wires will determine why the GEN light stays on and how the system is sensing inadequate voltage.

There is a way to recalibrate a Delco VR but quite frankly I could not be bothered with a correct looking VR on my Jane and went to a 715.

Apparently your j. block was bypassed but that's not an issue now aside from cosmetics. But it would annoy me. Test the alternator? Well you know it's charging but the VR may be limiting it or it's toast. Perhaps a diode. I have them rebuilt and don't trust remans after the butchery I saw in one. Old brushes and dried out bearings in a shiny case.

[Damon]

At home now, Before I start the engine 12.46 volts.  Start the engine and idles the same, 12.46 volts.  Rev the engine to 2,000 rpms and I get 13.2 volts.  I get 13.20 volts behind the alternator and at the red wire at the VR.  Battery reads about .10 less at 13.10 volts.  If I disconnect the positive terminal from the battery at idle the engine dies.  Im thinking my rebuilt alternator is junk....

[Sauron327]

I'm betting you are having the alt tested.  715's are cheap too. Put in the good alternator, see what happens. Then put in the 715 if still a problem. The housing on the 715 MUST be grounded. 14.2 volts is your goal. How is the battery anyway? If this is still giving you grief you are going to have to get a multimeter and start checking various wire voltages.

[Damon]

So I removed the (rebuilt) alternator to bring it to a shop and have it tested and fter it was removed I noticed a stud not beng used that read "ground".  I reinstalled the alt. and ran a wire from the ground stud to the negative battery terminal, no difference. I thought that was it as the heads are aluminum as well as the water pump.  The alt is a Delco Remy brand.  Battery is brand new.  Will update everyone after I have the alternator tested.

Thanks,  Damon

[Stingr69]

I would be tearing it down to check the diodes. They should all have continuity in only one direction, not both directions. You may have one that goes both ways.

-Mark.

[JohnZ]

If the regulator and alternator are working properly, you should show 13.5-14.5 volts across the battery terminals from about 1200 rpm up; that says the system is charging.

[Damon]

Thanks for all the help and advice.

Taking alternator in to have it checked today and will report results.

One other question, my dash has an engine temp dummy light. I found the wire in the drivers side of the engine compartment.  Need to buy a new sending unit, questionis where does this sending unit go?  Head or intake?

Thanks again,

Damon