85fortheDrive

Folks:

I've read the recent posts from Dennis Burford and 928SS about low voltage readings. As the electronics gurus on the board know, I've had similar problems. Perhaps this similar thread can provide evidence and solutions for all of us suffering from this species of electronics gremlins...

WHAT I'VE EXPERIENCED
The voltage gauge typically shows 13.5V. Drops to 12.2ish when headlights are on.
When I start the car when the engine is still warm (and this is more common in wet weather) I sometimes get <10V on the gauge. More recently, the gauge has soared past 16V as well. In these cases, driving the car for 3-5 minutes returns it to proper voltage. However, revving past 3K doesn't necesarily do an immediate fix to either the too-high or too-low situations. In cases when the car starts up with <10V, the warning light is sometimes flashing and the low voltage light is NOT on when the key is turned the the ignition point.

With increasing frequency, the speedo needle just wags without response until I've driven the car for about five minutes. This is more common on COLD starts.

I have magic blower syndrome, which I believe is unrelated, but which is nevertheless an electrical anomaly at startup.

WHAT I'VE DONE
New Bosch alternator, AutoZone battery, battery ground strap, engine ground strap, ignition switch, replaced all fuses.

Have cleaned and put contact improvement spray on all ground points in the car. Have done all parts of Wally's annual maintenance checklist except checking relays.

Have removed and cleaned PCB circuitry, checked continuity of printed circuits, and checked for working of all indicator lamps.

MY THEORIES (as a non-electrician)
1. Something is wrong with the key-ignition part of turning the car on.
2. There is suspect wiring within the printed circuit board.
3. The wiring junctions that feed into the PCB are faulty.
4. The wiring harness is experiencing continuity issues that are impacted by wetness and heat.
5. The 14-pin junction point at the + post in the car is problematic.
6. The Lord is causing this to happen in punishment for my ditching Becky N during senior prom.
7. Likes don't actually repel.

MY THANKS
To Alan, Dave McKenzie, Dr. Bob, Rog and all those who have continued to lend advice.

checkmate1996

Maybe I'm oversimplyfing here, but what about the internal voltage regulator on the alternator going bad...

Chazz

How do those readings compare to the voltage measured between the jump start post and a good ground in the engine compartment using a multimeter?

checkmate1996

my bad...I just saw that you replaced the alternator..

JHowell37

What about the exciter diode on the back of the instrument cluster?
What is the condition of the positive lead from the battery?
The ignition switch you replaced is the source of electrical problems, not the keyed lock cylinder.

If there are ongoing problems such as the 14 pin connector at the jump post, then now would be the time to address those problems. That may or may not solve the issue, but nonetheless, it's electrical, and you are having electrical issues, so the best way to troubleshoot the fluctuating voltage issue is to fix known problems that might be causing the voltage fluctuation.

Airflite40

I think this is just what the doctor ordered:

http://members.rennlist.com/sharkski...04-Bzzzzzt.htm

Alan

OK - so first - you've got to stop looking at the guage and assuming it telling you anything meaningful... just stop it!

So get a real voltmeter (DMM) and connect it where you can see it in the car and connect it to the top of the central electric panel (real ring terminal to the post with the red wires) and to the ground point above the CE panel. Monitor the voltage while you are driving and see if it does the same as the guage.

If the guage is accurately reflecting whats happeing at the CE panel then you have a supply issue to that point. if the guage still fluctuates but the DMM doesn't you likely have an issue in the pod connections or the voltmeter itself. Given the occasional other warnings it sounds like its more than just the voltmeter though...

Its possible its the pod grounding so pay particular attention to that... otherwise pod connections...

If both meters read similarly you will neet to perform the same test with the DMM connected to the battery directly (at the rear)

Let us know what you find...

Alan

85fortheDrive

You have my word that I will hook in a DMM and use it to gauge actual voltage.

I can tell you that when the voltage soars past 16V, both interior and headlight brightness increase. So I'm pretty sure this is not gauge related. But I will do my homework here as a next step.

I did find a Nichols blurb on this - http://www.nichols.nu/tip317.htm - but it's like my post - more a statement of the problem than a solution. There's reference to a fishy diode in the pod. If that is shoddy, can it cause a deterioration in the voltage regulator? If so, then even my new alternator my be sufficiently deteriorated now. Just wondering...

Thanks so much, Alan!

Pax,
Tim

6mil928

After reading the battery on mine. It reads 3-4 volts low. It is one of the reasons I'm pulling the pod and swapping the guage cluster. Also some PO has jacked with it.

Alan

Tim - there is no diode - I think he means the exciter resistor. Its possible you have an issue (again) with the alternator/regulator but I really don't know what would be killing them - shouldn't be anything in the pod. The primary suspects are excess loading related - which would be battery and aftermarket equipment (audio or other high current) usually. Certainly could be other high current consumers on the car - like ABS pump etc...

But there aren't so many of these...

Monitor the voltage for a while and report what you see.

Alan

Landseer

Building on Alan's point,

Have you ever pulled the CE panel out and inspected the wires on the back of it for melted insulation? ( really not hard to perform this extraction)

Same with the wires of each of the A --- Z plugs --- any melted insulation?

Same with the ground wires located in the region behind and above the CE panel?

Airflite40

Seriously!!!!

http://members.rennlist.com/sharkski...04-Bzzzzzt.htm

trust me do this it will give you piece of mind!!

6mil928

And a Migraine

SharkSkin

Alan's suggestion of checking the voltage at the panel is a good one, but the 84 panel is the last of the early style with the ceramic fuses and the main power leads coming in the front between plugs N and O rather than studs on the top edge like the later style. You can check it at any of the three big red terminals you'll find there.

The idea is to divide and conquer; If you don't get stable voltage there, you work back through the jump post, alternator main output terminal, and battery to see at what point it begins misbehaving. If you DO get stable voltage there, then you move forward through the panel, harnesses, etc to narrow it down.

Did you replace the alternator before all this or did the symptoms appear after changing it out? Either way, check for a slipping belt. That could cause low voltage under load and much higher voltage when the belt heats up and begins to grip, and it charges like crazy to make up for the time it wasn't charging.

If the problem seems to be in the CE panel/harness, try just unplugging and reconnecting each harness connector at the base of the panel. If this changes things, then it's most likely corroded contacts(and not just the ones that lead to the gauge) and you can choose whether to leave it at that(band-aid) or go for a more thorough approach.

And BTW, thanks for the plug, Borys.

Weo

I'm new to this and still learning, but I thought I'd pipe in with my experience and opinion.

I have a 1980. I've had the instrumental panel replaced a couple years ago. The voltage on the gauge always ran low, even more so with the headlights on or at a cold idle. It always turns on my warning "!". My prepurchase inspection confirmed that the voltage was OK, and that both the old and new gauge were off. Additionally, I had an aftermarket stereo installed a few years back which has a voltage meter LED near my battery. It confirms that I am getting about 13.5 volts when my gauge is reading 10 or less.

Also, my speedometer has gone out in the past. I believe it was a loose connection caused by me adjusting the steering wheel over and over when I first got the car. I've heard that adjusting the steering wheel height can loosen the connections to the pod. Since reading that, I had my connections checked and keep my steering wheel where I want it, and haven't had a problem since.

I could be plain wrong with these experiences and assumptions, but I'm sure someone will correct my mistakes. I just thought I'd comment. Good luck!