Charging light issue
 

Hello all
Car is a '79 SC CIS used only once or twice a week at best

When not used for a while, the charging light in the dash will stay on after starting. Rev the engine up and it becomes brighter. Rev the engine beyond 4,000 RPMs, light will go off for a while then it does it again at lower revs

Usually will do the above for a while then it goes off all together (regardless of the revs) after 1/2 hr of driving or so

Is this a brushes issue or diodes or something else?

It is not the regulator, I checked the voltage before the regulator and it shows 13.8 or less when the light is playing up

Thank you
Rafik

You need to put a meter on the battery terminals. See what the charge is. 12.5+ at rest, 13+ at idle, up to 14.2 at 2500 rpms.

Could be the battery, the alt or voltage regulator.

Could also be dirty commutator rings or worn brushes.

The indicator current, amps, normally flows from the battery through the indicator bulb to the slip rings/brushes to provide the initial magnetization of the rotor. Since the indicator glows brighter with RPM it becomes highly likely that the alternator is generating a much higher voltage than required,

If not a VR failure then a poor + or _ connection from the alternator to the battery Most commonly at the starter solenoid, or engine ground strap.

Cranking slow? Shorted battery cell.

Actually sounds more like excitation is not occurring through the VR circuit to get things going. Brighter lamp means more flow from the battery through the lamp not being cancelled out by the blue wire from alternator balancing the voltage.
Once the VR wakes up, it works normally?

Put a cheap digital voltmeter that fits in your lighter socket to see what voltages are being generated when it is doing it and post the results.

Original metal can remote VR beside the CDI under the cover in the engine compartment?
New electronic one from our host is pretty cheap.

thanks for all the advice.
I will get some more readings as described above and post the results
Battery is 8 months old
VR is the original
The car sat for a while before I bought it and put it back on the road so had many bad connections. For example the indicator arrows on the dash were all over the place. Once I cleaned the ground, they work perfeclty

After sitting in the garage for one day, here are some readings

Engine off
Volt at battery terminals is 12.7v

Engine on (2,500 revs)
Charging light in dash is on but dim
Volt at battery terminals dropped to 12.0v
Pulled the plug off the VR and measured across, volt is steady on 11.6v regardless of revs

Does the above tell me anything? Alternator stuffed? Brushes or something more sinister?

Did you take it for a drive to where the light goes out completely and check voltage?
I would try replacing the VR with the new $45 electronic one as a cheap replacement for the old mechanical one.

First one here:
http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2014.cgi?SUPERCAT_FLAG=Y&make=POR&Conte xt_make=&please_wait=N&LastVisited_input=911M&Prev ious_Section=&forumid=&threadid=&command=DWsearch& description=Voltage+regulator

A good rebuilder will help you....

Seems the voltage regulator is a miss!!

Timmy2, haven't taken it for a drive yet. Will do soon and remeasure

Rafik i Have the same car the same year,been dealing with this issue for months,replaced altenator, new regulator,still have the same problem ,checked all connetions clean,and tight ,ive come to the point i dont pay attention anymoore, the car runs great ,charges good, never leves me stranded, if you ever find out what the problem is please let me know ,Thanks TonyG

Hi Tony, when you say you had the same problem, you mean the dash light or also the low charging voltage (12v) at the battery?

Mine is dash light glows as you rev the car ,when you idle light goes out. charging good,thanks TonyG

Drove the car for a while till the light went off completely then remeasured
Engine running
Volt at battery terminals 13.5v
Volt across the VR plug terminals is steady at 12v regardless of revs

Sounds like the mechanical VR is sticky. Swap it for an electronic one.
You won't measure much of anything across the VR terminals, unless you go black to ground to see what the excitation voltage is.
The 13.5 volts running with lamp off is the real indicator the VR is working, it is just lazy. ;)

Not getting far with this. I had another VR which I fitted but exact same problem. The 2nd VR is not new but the chances both of them are faulty is slimi

To close this off, it was the alternator. Pulled it off and removed the brushes, looked worn. Got it fully reco'd. No more problems with dash light and charge at battery is 13.5+