Pulsating electrical

So I’ve known about this since I bought the car and while it isn’t anything more than an annoyance, at this point, it’s still annoying. I’ve gotten different answers from different people, either that it’s a problem with the alternator or the voltage regulator. Based on the pulsating nature of it, to me it seems like a voltage regulator thing, but I would love to hear from y’all experts!

First here’s a video of it:

http://img.photobucket.com/albums/v224/toomanyhelicopters/car/a8d35773.mp4

Second, it is not an all-the-time thing. It will always happen right after starting the car, then after a while will stop happening and then start again, which seems to suggest it only happens while the battery is being charged, no?

So! What is the source of this problem, and what is the solution?

Thanks!!

My '71 did exactly that for a while, it lessened at 3000 rpm, but was worse at 2000, and noticeable at idle.

It went away when I changed the alternator.

Well worn spots on the alternator is what a couple guys here suggested when I described the problem to them last year, if I remember right. I dunno, it was a bar, and I was on my 65th beer, so…

I don’t get how it could be the alternator though, and come in and out. Isn’t all the electrical being powered by the alternator at all times while the engine is running? The pulsating effect cycles on and off. Why would it ever stop happening?

And to be clear, I’m not doubting or even questioning your experience. Just trying to understand the mechanism behind this effect, and better understand how cars work. :slight_smile:

Thanks!

Scott

I’ll bet that if you’d check your chassis grounds, you’ll find that they are either missing or corroded. Without a good ground path, electricity does all sorts of funny things. I once saw a car’s accelerator cable get red hot because that’s the only thing that was acting as an engine ground when the car was cranking! Without a proper ground, your charging system gets funny signals, too!

FWIW, that is also one of the reasons that the factory neg battery cable had a grounding lug that bolted to the chassis using one of the voltage regulator mounting bolts.

I’m gonna check the grounding for sure. On the way home from shopping, the car started acting super weird, doing a few things it’s never done before.

First off, the horn started honking sporadically. Never done that before. Seemed to do it more when I was stopped at red lights idling, in an attempt to maximize my embarrassment. First chance I got I pulled over and disconnected the horn-- only one of two was connected, the other one is shot so has to be disconnected for the good one to work.

Second, it started hesitating when I gave it gas from a stop. Never done that before but was doing it consistently.

And third, after sitting in the CVS parking lot for maybe 10 mins, after driving for several miles, it really didn’t wanna start, and when it did, it was trying really hard to die on me. Had to work the gas pedal for several seconds to get it to the normal smooth idle.

Very frustrating. When I got it home, I left it running and took some voltage measurements. Here’s what I found.

Lights, heater, stereo off:
15.1 to 15.4 VDC, bouncing around, with 220 to 270mv AC ripple also bouncing around and occasionally dropping to 0 for an instant.

Lights, heater, stereo on:
14.7 to 15.7 VDC bouncing around, and very wild AC ripple jumping all over from 0 to 400mv

Car and everything else off:
13.2 VDC dead solid
0 AC



So. Ground, alternator, diodes in the alternator, alternator belt slipping,something else? And the hesitation when I give it gas from a stop, possibly related to likely not?

Worth mentioning maybe, the electronic choke is still hooked up to the ignition coil connection on the solenoid which I know is not cool, but I haven’t had a chance to run a wire to a key-on fuse yet. From what I understand that is messing with my coil voltage and means the plugs aren’t getting the juice they should. Is that part of this whole issue or just amplifying it?

Based on those voltage readings, something is obviously wrong in the alternator/voltage regulator part of the engine right?

I’ll bet you still have one of the old points style voltage regulator. I believe an electronic regulator would help.
I’ve used a 2000 Taurus alternator in a similar application for an upgrade. Pick-n-pull is full of them.

Stock ignition to the best of my knowledge, though an Ignitor 2 system that a friend has for sale is scheduled to be installed soon. But the voltage regulator isn’t part of that, right? Separate thing for me to address? Is the voltage regulator a blue box on the driver’s side mounted just behind the headlight? With a capacitor/condenser on the top of it? The first thing I’ve thought with all the AC ripple I’m seeing at the battery is a bad filter cap, but that might just be me going to what I’m familiar with from the tube amp world where I actually know something. :slight_smile:

Here’s something else I just noticed which I assume is totally unrelated, but…

Here’s a pic from last year:

And here’s a pic from today:

There is a discoloration on the piece where the throttle cable attaches to the carb, which is new, and the same sort of discoloration on the valve cover just beneath it which I don’t know if it’s new or old. That’s not got anything to do with the pulsating electrical I’m sure, but I just noticed it so I’m throwing it out there for comments I guess. Problem?

And something that I’m wondering about now, the cable from battery negative to the block is connected solidly on both ends as far as I can tell, but it’s stretched kinda tightly. Is that normal? Doesn’t seem like it would be. Problem? New cable needed?

Thanks again for the help.

And the video of the alternator replacement on the Taurus, just a guide for replacing the alternator if it comes to that?

Was your problem ever resolved?

Ron

Not even slightly. This just happened today.

Two other details I just remembered.

There was another electrical issue. When I went to start it maybe the third or fourth time before this, when I turned the key I heard the solenoid move and then nothing at all. And the interior lights weren’t on if I remember right. I hit the solenoid a couple times not too hard with a rubber mallet and it started right up and didn’t have that issue since.

The solenoid is new as of last fall, I was having the same sort of issue where a hit from a mallet fixed it. But I figured it’s a mechanical device, and old, so wear and tear.

Now I’m thinking it was probably a grounding issue that the shock from the mallet would temporarily resolve, probably nothing to do with the solenoid. I should’ve had DC supply rails set up, but it wasn’t really possible at the time. With the new garage, I can do all kinda great stuff, but right now it’d be fixing a brick wall problem like this, or unpacking boxes and figuring out what goes where.

The second thing, where do I find the top-notch write up of how to correctly wire an electronic choke to a fused, switched outlet? I just had this problem with the Bronco I bought, and there resolved it by disconnecting the power to the stereo and running a wire through the firewall to the choke. That thing starts like a champ now, I even reconnected the linkage for setting the high idle. Starts spot on.

I already want to run a feed through the firewall, to send manifold vacuum to the old Sun gauge I bought that fits perfectly where I took the rally clock out. The fuse box is not so user friendly here, right? Where’s the best place in the fuse box to connect up a feed for the electronic choke? And please don’t say the stator post because from what I’ve read of the voltage that puts out and the voltage requirements of the choke, it’s explicitly not okay. Maybe I got it wrong and it’s not Edelbrock just Holley that says it explicitly, they say “do not use the stator feed from the alternator” in so many words.

The right way is a fused feed from a run-position-on circuit, or even better, using that fused feed to switch a relay that either gives a direct connection to battery red or doesn’t, right? So I need a wire through the firewall there?

Also maybe related but probably not due to distance from the impact of the mallet… I got a new wire for the tach and temperature sender, got it with a bunch of other parts for stuff I’m gonna be doing ASAP, new fuel tank, PCV valve and valve covers too. No more tin with a cork gasket and some yahoo cranking down the wingnut-tipped bolts. Aluminum and normal freakin bolts.

I got the tach wire cause the one that’s there is, I suspect, the original, and it’s pretty ratty looking. So is the wire to the coil, really.

But the coil wire, how could it cause the lights to pulsate? Short in and out, ok, but follow a really specific interval of growing brighter then going dim? I could see the startup problem being related to the coil having an intermittent shorting thing goin on, but the pulsating lights are for sure a separate issue.

New fuel tank and lines. Got em. Just waiting to get this tank down a little more. It’s at about 1/4 tank, on the gauge anyway. Lowest I let it get so far. I don’t think I ever got it much below 1/2 full. And gotta deal with other stuff first, I guess. But restricted fuel flow or dirty carb, are those the two main culprits for the hesitation from a stop I had mentioned? I think a weak spark is another, and there the electronic choke thing could be a problem, right?

I’m stumped. I gotta get back to work too, made some promises to the boss about what I’d have done for Monday, and tomorrow being Easter and all…

Showing what the Taurus 6G alternator looks like.

Ah! Is that the alternator to put in mine, you mean?

But wait, idler pulley?

You MUST have a battery-to-chassis ground as well as a battery-to-engine block ground. Think about it. Your voltage regulator is mounted to the chassis. Your lights are mounted (and grounded) to the chassis. Without proper grounds, weird things happen!

I had the same problem with AlphaCat years ago… When I built up my car’s original engine, I replaced my battery cables with 0-ga. One from Battery + to solenoid, one from solenoid to starter and another from battery neg to engine. All sorts of flickering, to the point of once I blew out just about every lightbulb on the car. I tried different alternators, I tried different voltage regulators (including solid-state ). Then I added another 0-ga ‘ground’ cable from the engine block ground bolt to the framerail and all pulsing stopped. That also cured my weird rear turn signal sequencing issues. It all came back to no chassis ground!!!

I did measure the resistance from the chassis (where the hood release is) to the negative battery terminal and it read just barely over 0, so, what it should have. But I am up for trying adding a single wire. If that solves my problems, that would be most excellent. And it can’t hurt.

I agree with double checking and upgrading the grounds all over the car. My dad’s truck had a bad negative battery cable. It would start and run fine, but die as soon as you turned on the headlights or hit the brakes. Anything that drew a load more than just the engine running would over do it. That one had me scratching my head for a while.

Here is a write up I did a few years ago about electrical upgrades on my daily driver and the effects it had:

http://www.ford-trucks.com/forums/289070-made-the-3-upgrades-night-and-day-difference.html#post1986798

Does this car have a name?

Hey Fordblue thanks for that link, will give it a good read today.

Car’s name is Diane, in reference to the microcassette messages in Twin Peaks.

Should be an OEM chassis ground located on the rear RH cylinder head attached to the firewall with a large (3/8 hex) sheet metal screw. I’ve seen throttle springs glow red from poor grounds…

Read the write-up about replacing ground wires and battery. I think my battery is good, a relatively new Interstate. The ground wires probably not so much. I will check the one to the firewall, hopefully today.

Grounding wouldn’t likely lead to consistently periodic pulsating electrical though, right? To me it just screams of a RC circuit where I’m seeing the capacitance charging but shouldn’t be. Doesn’t that suggest the voltage regulator? I would think if it were diodes in the alternator the period would repeat much much faster than it does, more like the same as the engine rpm, no?