Team Chevelle banner
1 - 5 of 5 Posts

· Registered
44 Posts
Discussion Starter · #1 ·
Hey guys...

Checked my charging system account 11.98 VDC at battery, engine idling, no lights/accesories on. Checked voltage readings and found this...

At extenal voltage regulator...

Key OFF / removed from ignition - Regulator plug removed - 12.8 VDC at battery

F (blue) = 0
2 (white) = 5.38 VDC
3 (red) = 12.77 VDC
4 (brown) = .008 VDC

Key ON / engine not running - Regulator plug removed - 12.4 VDC at battery

F = .004 VDC
2 = 5.32 VDC
3 = 12.23 VDC
4 = 10.73 VDC

4 brown dissapates voltage, after key is OFF / removed, slowly at a rate of .3 to .5 volts per second until it reaches .008 VDC.

At this point, I STOPPED and removed both battery cable connections and ohmed the blue & white wires between the altenator and regulator (both had 1 ohm resistance). Waiting for wiring diagram to arrive prior to poking around any further with my multimeter.

It's a 1969 SS, 396 auto, factory non-A/C car. Factory tach & gauges. Bought the car and parked it over the winter so this is the first time I really poked around under the hood.

Other known problems...

Ammeter AND Oil Pressure gauges inoperative.
Ammeter needle stays at first line towards Charge (off center) at ALL times (key OFF, ON, engine running).
Oil pressure needle stays half way between center and HIGH at ALL times (key OFF, ON, engine running).

There are only two wires at junction block behind battery, both heavy gauge Red.

The Field and Relay plug at the alternator was cut & spliced, the plug has Light Grey and Dark Grey wires spliced into two black wires. Followed the two black wires and the BATTERY red wire behind left side radiator, that harness exits behind the battery as BATTERY red, Relay white, and Field blue (splice somewhere along radiator) Battery red goes to J-block and meets ONLY heavy red from battery. Blue F and white R u-turn back to voltage regulator.

Regulator case has a good ground at core support.

Engine was cranking slow, but starting, which caused me to check charging / cranking system in the first place.

Heater blower fan inoperative on HIGH, turns slowly at other positions.

No other hokey cut/splice wiring apparent under hood.

I searched this forum and haven't seen anyone else with these voltage readings at their regulator plug. The readings immediately caused concern, especially the 2 white (5.32) and 4 brown (10.73) with key ON engine not running. The wiring schematics won't be here till the end of the week, so I was wondering if anyone can start me looking in the right direction. My last car, a 71, had newer parts (internal regulator, HEI, aftermarket gauges/voltmeter) so I'm not familiar with a 69's electrical workings yet. I'll check back during the week and post any results...thanks in advance guys...ya'll have been ALOT of help since I joined the Team...Rob

· Premium Member
125 Posts
F=Field variable voltage depending on load
2=Stator connects between the output diodes, ½ charging voltage, 0 when not running
4=Alt light to ignition or resistor to ignition if gauges
To Full Field Alternator disconnect regulator and short 3-F “Full Field”
Warning this will not be regulated and if the battery is fully charged voltage will quickly climb to 18v and beyond.
The Stator is ½ charge voltage when running. Usually either 0 or ~7.
The fact that you have stator voltage when not running indicates either a sensitive voltmeter or a shorted diode.
4-Light well you know when you shut off the car the Alt light slowly dims out. This is what you are seeing.
To check the charging circuit you must be around 2000rpm or higher. Good Battery
If you just started the car voltage could be low especially just after starting and at idle.
Start and run the car at 2000 rpm until the voltage no longer rises. Depending on temperature the voltage should be ~13.5 – 14.4, the stator voltage should be ½ charge voltage, the light should be 12v to oppose ignition voltage and turn the light out, the field voltage will bounce around (1-13)

Advanced Ignore: Sometimes if you cross ignition circuits through aux radios and stuff the car will not shut off. You can place a diode in series in the light circuit to prevent “back flow” This is where you have shut off the ignition switch and yet the car continues to run because the regulator is “back feeding” the ignition circuit.

· Registered
44 Posts
Discussion Starter · #4 ·
Mark and John...

Thanks for the replies.

Per previous owner, car was a factory Non-A/C with factory tach & gauges when he bought it around 1990. No major surgery done to car for over 5 years. I ASSumed this was true account no A/C equipment under the hood, could've been removed & blocked off 2 or more owners ago. Haven't yet poked around under the dash. I thought I'd throw in the blower fan not working on HIGH as informational purposes only. The Ammeter and Oil gauges not working made me wonder about wires crossed between the engine & dash/cluster, also causing the charging system issue-voltage readings I got. I'm using a Fluke Multimeter with a new 9 volt battery and good test leads.

I came across Peter F's and Charbilly's diagnostic procedures for external regulators/alternators and ran them. I was worried about the Key ON engine not running figures. My tests indicated voltage at 2 "white- Stator" when the tests indicated there should be zero "0 VDC". Also, F "blue-field" and 4 "brown-gauge" didn't correspond, F was .004 VDC and 4 was 10.73 VDC, when the tests indicated they SHOULD be "slight voltage" or equal to each other. :eek: I did a double-take when I saw 10.73 volts and stopped right there, thinking that was way too much to be "slight" or equal to the F-blue-Field measurement. Ya'll are thinkin' the 2 "white-Stator" reading of 5.32 (approx 1/2 of 4 "brown-gauge" 10.73) indicates a bad diode in the alternator? :confused: The Fluke meter's sensitivity shouldn't skew 2 Stator wire's reading that bad, should it?

Would this voltage 4 brown and it's dissapation rate indicate incorrect/crossed wiring between the regulator plug-ignition coil-ammeter-instrument cluster, since Ammeter in dash isn't working either? I suppose that's a dumb question since ya'll aren't here under the hood...anything's POSSIBLE given multiple owners and 35 years of tinkering...just thinking/guessing out loud.

I'll try the engine running-fully charged battery tests ya'll suggest and get those results next. We've got another month and a half of winter up here, so I've got time before cruisin' season starts up. Just wanted to get the electrical system checked out and up to par BEFORE adding any Mark VIII/Windstar/electric fans-10SI internal reg'ed alternator-HEI ignition installed. The blower fan-oil gauge-turn signal sockets' bad grounds are secondary to any charging/starting system problem I may or may not have.

Thanks again for the guidance and replies. I'm kinda "blind" right now without wiring schematics nor experience with a 69's electrical systems. I work over-the-road for a couple days at a time so I'll do a little further testing when I can and post back with the results. Electricity isn't my strong point, so your help and suggestions are greatly appreciated.
Every problem HAS a solution...Rob
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.