Interesting Electrical/Charging Issue Options

[GregAmy]

1974 2L 914. "Driver" condition, way far from concourse, but drives well. I've noticed from the beginning a relay clicking under the dash; at first I thought I left my turn signal on, but it's not. It didn't seem to bother anything so I ignored it.

Couple nights ago I drove it for the first time at night. It was then I noticed the "gen" light was glowing very faintly, and at idle I'd hear the click and the light would get brigth(er), then slowly dim. Then it would click again, get bright(er), then dim.

I've also noticed from the beginning that the voltmeter would show 13+ volts normally, except when I stepped on the brake; when I did that it would go below 12. Same thing happened when I flipped on the lights. Strangely, when I did either, the clicking would stop...

Today I did some basic troubleshooting. Had my assistant sit in the car and I measured voltage directly at the battery. At idle, center console gauge shows ~13v, VOM showed 13.75. Good. Asked Vanna to step on the brakes; gauge showed ~11.8V, battery showed 13.4. Asked her to turn on headlights and stay on brake; center voltmeter showed ~11.5, battery had 12.3-12.5. Asked her to rev it, battery voltage got up to ~12.7.

So it really doesn't sound like I have a charging issue, it sounds like there's something going on under the dash.

I'm gonna guess you're gonna tell me it's a ground under the dash. But can you offer where I might find that? Or where I can run one to supplement it? The battery (from a Miata) has been moved to the rear trunk; it's positive cable goes directly to the starter and its ground to the ground stud under the rear trunk. The ground strap from that stud to the transaxle is very good, I've removed, cleaned, and re-attached it.

Car seems to be running fine, starts, drives, charges. I'm just looking to get accurate readings from the gauge and to stop that clicking...

Thanks!

Greg

[Tom]

The ground lug is under the dash near the fuse panel,
The voltmeter in the console is a bad design the way it is hooked up. There is nothing wrong with the readings you are getting. To accurately tell one the voltage level of the battery, they should have run a dedicated wire from the battery to the voltmeter.
Your problem sure does sound like bad grounds.
Tom

[GregAmy]

I love me a good electrical mystery...

So read up there ^^^ on my questions about charging. "TL;DR" is that my battery is charging fine, but the gauge in the center console is wrong. Fine, no prob, I'll get around to adding a dedicated wire from the center console to the starter/battery to give me a good reading. But that dim/flickering generator light and the relay clicking caught my attention...

I printed out the full wiring diagram and started looking. It made no sense, that I had some relay clicking under there in time with the gen light. Couldn't figure it out (foreshadowing: still haven't) but I started looking around on what could cause that and noticed the flasher relay is using the same power circuit...a clue.

I got home tonight and pulled down the fuse/relay panel and looked around, all seemed well. Ground from there to the chassis was strong, no corrosion and 0 ohms resistance to other points on the chassis. Fired up the car and noticed the gen light flickering once every second or so, along with a click. Basic tactile search revealed it was the flasher relay.

Pulled the relay...and no more clicking (of course) and no more gen light flickering. Plugged it back in and noticed the relay was buzzing along with the occasional click. Replaced the flasher relay with a spare and the relay and it started clicking at the same tempo as the turn signals -- and the gen light flickered as if it were a turn signal indicator.

Final clue: I tried the turn signals, and the T/S indicator flickers in time with the signals (which seem to work fine all corners) but then stops lighting up after 3-5 times.

Something really strange is going on here. Since the gen light works fine with the T/S relay removed, I'm guessing it's something in the turn signals/emergency circuit that's no right. Bad ground, swapped wires, something that would cause the relay to flicker on and off and cause the gen light to illuminate. The gen light works off of differential voltage, so I'm wondering if the supply amperage to that circuit is insufficient? all of it is fed through the 15 keyed circuit; bad ignition switch? Or maybe the turn signal circuit has some oddball ground that is sucking up the amperage?

Remember: turn signal flasher removed, gen light works fine. Slip it back in, relay buzzes and/or click along with the gen light. Go.

All the makings of a good murder mystery. But given I have a lot of other things to deal with in my life, if you've solved this before please toss the answer at me...

Greg

[Spoke]

Gen light doesn't come on when the headlights are turned on?

[toolguy]

Hook up you VOM where the console battery gauge is and confirm the correct readings there. .
If you read different than what your read directly at the battery, you have a voltage drop in the wiring harness or the ground. . and I'd bet on the ground being a poor connection first.
You can wire the meter ground side directly to a new frame ground right above the console on the bulkhead. . there should be a 6mm stud where the radio brace goes. .

[stugray]

Sounds like you have a "soft short" in the flasher circuit.
(soft meaning it is a load, not zero ohms or "hard" short)

When the flasher circuit is energized, it pulls so much current that the voltage is drooping on that side of the Alt light circuit.

A voltage difference in either direction is what makes the Alt light illuminate.

You could tell which side of the alt light the drop is on by checking the voltage across the light when it is lit.
This will tell you which way the current is flowing and help you isolate the probelm.

[Mike Bellis]

Sounds like you are chasing 2 different problems.

Clicking is most likely the brake circuit. Either check the switch at the e brake handle or push the reset button on the master cylinder.

The voltage drop you see an the gauge is mostly due to age. All of our chassis grounds are rusty and corroded. The ground plane of your car used to be the entire unibody. After 40 years, it is spot welds and steel panels. The factory volt gauge should have a dedicated wire from the battery but it shares with all the other accessories. Clean your grounds and the reading should improve.

The other factor is corrosion on the old wiring harness. Even if it looks good, it's still 40 years old, on a design built for a ten year life span.

[GregAmy]

Gen light doesn't come on when the headlights are turned on?

Nope. Behavior is the same, with or without additional load.

Sounds like you have a "soft short" in the flasher circuit....You could tell which side of the alt light the drop is on by checking the voltage across the light when it is lit.

Good point. I shall make that my next troubleshooting step. But note that since the prob goes away with the flasher relay removed, I suspect it's going to be on that side, downstream of the relay.

Clicking is most likely the brake circuit. Either check the switch at the e brake handle or push the reset button on the master cylinder.

Not sure why you say that? It's definitely the flasher relay that's clicking. When I remove the flasher relay the clicking stops and the gen light stays off.

The other factor is corrosion on the old wiring harness. Even if it looks good, it's still 40 years old, on a design built for a ten year life span.

Yup. If I can find the resistance circuit, I can repair/replace it.

GA

[GregAmy]

Sounds like you have a "soft short" in the flasher circuit.

And I wonder if this may be related?

http://forums.pelicanparts.com/porsche-914...al-problem.html

An incorrectly-grounded wire would explain one relay "buzzing" and the other cycling and causing the gen light to cycle.

So in addition to checking everything else, I guess I'm pulling out all the turn signal circuits to ensure they're terminated correctly...

GA

[76-914]

I'm going to ask the same question as Mike B. in a round about way. Does the flashing red light on your gage function properly when the E-brake is engaged?

[ChrisFoley]

Check the wiring connections on your front turn signals.
One terminal is grounded to the light bucket.
Reversed polarity there will cause dash lighting anomalies.

[GregAmy]

Does the flashing red light on your gage function properly when the E-brake is engaged?

Dunno, I'll check it. HOWEVER, I see where you're going: you're thinking the ground may be in that e-brake circuit. And you may be on to something: when I bought the car it was (still) missing all the carpeting and a lot of the interior was removed, I believe to repair floor rust...and I do not recall seeing a switch installed for the e-brake, nor do I recall ever seeing a parking brake warning light coming on.

And, per the wiring diagram, if that circuit is shorted it could energize the flasher relay.

I'll investigate this lead as well.

Check the wiring connections on your front turn signals.

Will do as well, thanks.

Racing this weekend so don't know if I'll have time to follow up on these leads until next week, but I'll report as soon as I do.

GA

[Mike Bellis]

The flasher relay is tied to the brake circuit. That is why I ask. It is a warning function of the brakes.

[GregAmy]

Ok, so I had 15 minutes to check some things out.

- No switch on the e-brake handle. Hell, not even any wiring over there.
- Obviously, e-brake warning light not operational.
- Seat belt relay system is supposed to be under passenger seat, right? Right, nothing there.
- No brake warning light with the key on (oil and gen light are on). Don't even know where it's supposed to be...
- Don't know what you mean by 'reset the switch on the master'
- With the key on, I can hear the relay buzzing and clicking.
- Turn signals at all four corners work strong.
- Tried to find where the black/green/white wire splits off the relay, but it must be buried in the car somewhere.
- I reached under the car (it's on the ground) and pulled off the wire from the master cylinder and...relay buzzing and clicking stopped. Started the car...no more buzzing/clicking. Turn signals all still work fine.

So, it appears the problem is in the wire to the master cylinder. It looks like it has been repaired before, and not very well, so for now I'm going to leave it disconnected and tie-wrap it out of the way (I'm confident I can tell when there's a hydraulic brake issue). Next time I have it on the lift I'll follow the wire and see if it's chafed on the body somewhere.

Any idea where the seatbelt warning system disappeared to...?

[Dave_Darling]

The master cylinder switch is supposed to flash the brake warning light when it detects a pressure imbalance between front and rear brake circuits. Like what happens when a brake line fails catastrophically (almost unheard of with stock lines), or when you boil your brake fluid (rare), or when you bleed your brakes (relatively common). Most of these switches require you to reset them to turn off the light.

You reset them by pressing the button on the switch, which is covered by a rubber cover. Just press the cover in to press the reset button.

--DD

[Mike Bellis]

Ok, so I had 15 minutes to check some things out.

- No switch on the e-brake handle. Hell, not even any wiring over there.
- Obviously, e-brake warning light not operational.
- Seat belt relay system is supposed to be under passenger seat, right? Right, nothing there.
- No brake warning light with the key on (oil and gen light are on). Don't even know where it's supposed to be...
- Don't know what you mean by 'reset the switch on the master'
- With the key on, I can hear the relay buzzing and clicking.
- Turn signals at all four corners work strong.
- Tried to find where the black/green/white wire splits off the relay, but it must be buried in the car somewhere.
- I reached under the car (it's on the ground) and pulled off the wire from the master cylinder and...relay buzzing and clicking stopped. Started the car...no more buzzing/clicking. Turn signals all still work fine.

So, it appears the problem is in the wire to the master cylinder. It looks like it has been repaired before, and not very well, so for now I'm going to leave it disconnected and tie-wrap it out of the way (I'm confident I can tell when there's a hydraulic brake issue). Next time I have it on the lift I'll follow the wire and see if it's chafed on the body somewhere.

Any idea where the seatbelt warning system disappeared to...?

Seatbelt warning on 74 and later. What year is yours? Or did I miss it?

On the master cylinder, under the car is a reset button. You have to jack up, crawl and use a flashlight to find it. When you do, push it in. You might also have to remove the skid plate for better access, but usually can be reached without removal.

The brake handle switch is not in the handle. It is located on the down stop, or where the handle rests when the brake is off. If your switch is missing, the wire may be grounded which can cause the clicking.

The brake warning system is designed to tell you that the parking brake is on or if the brakes run out of fluid. It would normally flash a lamp on the dash. I have seen the lamp located in a gauge or in a warning lamp above the climate controls. It depends on the year.

There is also a diode in the system. The diode separates the brake warning side of the circuit from the signal lamp side. I have seen these fail to short which could cause the clicking.

The flasher itself works by completing the circuit to ground. The wire to the lights is grounded on the other side of the lamp. The brake warning switches also complete the circuit to ground. The diode above keeps the two circuits from back feeding to each other.