This one has me a bit puzzeled.
I has a dim gen light while the car is running.
I thought ok, changed the alt, still there. Hmmm,
fine, new voltage regulator, still there.
Funny thing, when shifting into reverse, it gets
brighter. Into drive, dim again.

It was glowing dim before I replaced the jetaway
with a built 350. I did remove the switch-pitch
pigtail from the accelerator, but like I said, it has
been on since I bought it. Doesn't seem to hurt
anything, new Die-hard battery seems to charge just
fine, but it really is bugging me.

66 442 vert. Pretty much stock, 400 E block,
30 over with a small cam. Runs great.

 

Is your idle too low?

 

Hi Eric, no I have been tuning on it.
I have it running at about 700 to 750 rpms at idle.

 

Have you ever measured the voltage across the battery terminals with the engine running at idle?


P.S. "Convertible" is actually properly spelled with a "i". I see you have added your new car to your signature block. Just thought you might want to have it correct if you're going to have that there for all to see.

http://en.wikipedia.org/wiki/Convertible

 

I don't have a '66 factory service manual, but I do have a '67, and here's what it says when the warning light fails to go out with the generator in operation. I'm assuming things didn't change much from '66 to '67 with regard to this.


1. Connect a voltmeter from the #2 terminal of the voltage regulator to ground.

2. Operate the engine slightly above idle speed.

3. If the voltmeter reads 5 volts or above and the indicator lamp fails to go out, replace the regulator.

Since you've already replaced the regulator, unless the new one is bad, which can happen, it would seem that this possible cause has been eliminated. It would still be interesting for you to check this and see what the voltage is.

4. If the reading is below 5 volts, connect a voltmeter from the generator "R" terminal to ground.

5. If the reading is now 5 volts or above, the wire between the generator "R" terminal and the regulator #2 terminal is bad.

6. If the reading is still below 5 volts, it says "proceed to generator output check."

Given that you've already replaced the generator, it would seem that it is not the problem, either, although rebuilt generators just brought home from the store have been known to be bad. But maybe that wire described in step 5 is the problem.

The "generator output check" section has 11 steps.

 

Thanks jaunty. I figured most folks would still "get it."

 

Both the Alt and Reg were known
to be good componets. Did I spell that right?
Both came from a running 67 Cutlass.
This is why I am at a loss with the problem.

 

Yes, the generator and regulator might be fine, but what about that wire that goes between them as described in step 5?


No, your spelling sucks big time. The word is components, with an "n" before the t.

Hey, you asked!

 

Ha ha. I will have to do some checking this
weekend. I will dig out the volt meter and
give it a cheek.

 

As in turn the other?!

 

Better fire up that old kerosene-powered spell-checker, too!

- Eric

 

Thought that might give ya a smile.

 

Check the fuse for your reverse lights....make sure you have the proper amp in there. If the light goes away in reverse, you may have found the problem.

 

Getting back to your gen light problem, it would be interesting to know what the voltage is across the battery terminals when the engine is running. I have a voltmeter as a dash gauge on my '67, and it reads 14-15 volts when the engine is running, and I think that's right where it should be.

The bottom line is that, however faint the gen light might be, the fact that it's on at all indicates current flowing in the wrong direction in your charging system.

I am a bit curious about why you replaced the battery (you mentioned a new Die Hard). Was there something specifically wrong with the old one, or did you just throw a new one in there hoping it would solve the problem?

The reason I ask, and I'm probably wrong here, is that I always thought that a weak battery is not something that would turn on the gen light. The gen light goes on because the battery is being discharged, not because it won't hold a charge.

A weak battery would manifest itself by weak cranking or no cranking at all when trying to start the car. But once started, the charging system takes over, and the battery just sits there quietly getting recharged. Whether or not it's actually taking a charge is a separate matter, but, as I say, I don't think a weak battery turns on the gen light.


Here's another question. You say the gen light gets brighter when you put the car in reverse, which is weird, but maybe reverse slows the engine speed enough to decrease the charging current enough to brighten the light a bit. My question is, does anything else make the light get brighter? What if you turned on every electrical device your car has? Start the engine and then turn on everything (headlights, hi-beams, radio, blower motor on high, windshield wipers, and open the door to turn on the dome lights). I mean, really tax the system. Does the light get any brighter? Or does it get a bit brighter you turn something else on? At least something that is a major current draw like the blower motor, wipers, or headlights?

If the answer is yes, I'm going to guess your system is right on the edge. It's barely keeping the battery charged, and the fact that you've put a new one in is only perhaps masking the underlying problem.


Here's a third question. You say the car runs and drives fine. What's the longest you've driven it continuously? In other words, things might seem fine if all you're doing is putting the top down and taking the kids to the corner ice cream stand. But if you took the car on, say, a four or five-hour drive, would the battery discharge enough in that length of time that you might have a problem trying to restart the car?

 

I don't follow the logic here.

He says putting the car in reverse brightens the gen light. That suggests that whatever problem his charging system has gets worse when the car is in reverse, and putting the car in reverse does slow the engine as well as turn on the reverse lights. But he could also simulate the added current draw caused by the reverse lights by turning on some other electrical system, like the headlights, instead, as I suggested. My guess is that he hasn't noticed an increase in the gen light brightness when other electrical systems are on, so the increase in gen light brightness caused by putting the car in reverse is not caused by the reverse lights themselves being turned on.

If he has too small a fuse, then putting the car in reverse should blow the reverse light fuse. That would open the circuit, meaning no current draw at all. That lessens the load on the system. I don't see how that would make the gen light get brighter.

Too large a fuse should have no effect at all as long as there are no other problems in the reverse light circuit.

 

Or maybe there's no ground strap on the engine, and the body is making ground through the shift linkage, and the resistance changes when in Reverse because of the positions of the parts.

- Eric

 

I think if he had a missing ground strap, he'd have more electrical problems than just a dim gen light. But I don't know. Electrical problems are the most insidious of any type of problem you can have with a car, and the solution often ends up being in the least-expected place.

 

Why, we have Jaunty.

This was posted by Joe P. in another post and is worded better than I would be able to explain it.

The GEN light does not ground in the instrument panel. The bulb is supplied with +12v with the key in the RUN position. The other side of the bulb is connected to the #1 terminal on the alternator (assuming a three wire, internal regulator alt, like the SI-family). In the regulator, the #1 terminal is grounded when the alt output is low and should be full alt voltage when the alt is charging. By having the same voltage on both sides of the bulb, it does not illuminate. If voltage on one side (and it could be either side) is low, current flows through the filament and the bulb starts to glow. The greater the voltage differential, the brighter the bulb. If the bulb is glowing dimly, you have a voltage drop on one side of the bulb. Start by checking output voltage at the #1 terminal on the alternator - it should be 13.8V or so. If you can get to the IP connector or the two terminals of the bulb socket, check the voltage of each of those to ground with the engine running. They should be the same. If one is lower, find the voltage drop in that wire. It will likely be a dirty connector terminal someplace.

The only difference is yours is an external regulator and the light is fed from the regulator connector on the firewall terminal #4, I think it's a brown wire. The brown wire goes through the bulkhead connector and then directly to the light. On the other side is a pink wire that also feeds power to your fuel gauge, temp light, parking brake light, and oil pressure light. So depending on which side of the light is low (brown or pink wire to ground) that will be the direction you need to go.

https://classicoldsmobile.com/forums...light-dim.html

 

I kept fighting a dim GEN light too. Checked alternator, replace regulator and cleaned a bunch of grounds but it kept coming back. Finally replaced the connectors at the alternator and VR and the problem went away. Picked up both pigtails at a local parts shop for just a few bucks each.

 

Cool Dane. I will try that.
The two part plug that went into
the alt was a bit toasty, I replaced
it with a better one I had, and the
brighter light just stayed dim in reverse,
go figure.
I also tried the old school trick of pulling the
pos. cable while running, and it died.
Me thinks alt is a pos.

Also, good ground cable from the back
of the block to the firewall.
Thanks all for the suggestions guys
I will get it figured out one way or the
other.

Jaunty, I drove it home from Fort Wort
the day I bought it, about 300 or so miles,
light was dim when I picked it up. He had
replaced the battery and alt beforehand.

Loaded it up with all systems including
brights and the a/c on high, no change,
dim light even in reverse.

 

Thanks. I was just about to retype that. You saved me the trouble.

 

Good point.
I just checked the diagram, and, yes, I can't come up with a way that a bad body ground would do this.


Or, if you're not obsessed with originality, you can just use any 1/4" spade connectors, soldered to the wires, with shrink tubing on the outside.

I did this on my alternator after I barely got home one night with a discharging battery, and the next morning found that the factory plug had fallen out of the alternator receptacle.

I would also remind you to be sure to clean the terminals of the regulator and alternator, as they're probably a bit corroded, too.

- Eric

 

Your quite welcome, I remembered seeing that thread when doing a search on 1 and 3 wire alternators some time back.

 

Same exact problem on my delta.....dim light, brighter in reverse. I had no fuse in the reverse lamp slot....put the correct one in, issue solved. Go figure....

 

It does seem that the reverse light switch is getting its power from the pink wire circuit feeding all the idiot lights. It shows that the junction of all the pink power wires is fed by an orange wire from the fuse block. Are the other lights acting up, do they light when you go to accy?

What also is a concern is that you pulled off the pos. battery terminal and the engine quit.

 

My generator light stays on too. After the ignition wire broke on the starter I got a whole bunch of lights that came and some warning beeper was going off like a ekg machine, darn car sounded like it was having a heart attack, lol...

 

I remember we used to pull the pos.
cable to check for a bad alt. If the
car died, new alt.

I got a new alt. and reg today
and the light is almost gone, very,very dim.

Did the oldschool trick and she kept running.
Everything works as it should, no surges, I did
see some hack work up under the dash though.
The trunk light is the only place I have no power.

 

FWIW, I had an intermittent, dim gen light in my car from the time I got it a few years ago. Sometimes it would stay on (dim) while I was driving and then come on bright when I was in reverse, other times it would just come on dim in reverse, sometimes not at all... no real pattern. The couple times I was ready to pursue it, it wouldn't do it. A couple months ago I resealed my intake manifold and it hasn't happened since then. I removed and reconnected the alternator and the ground cable to the engine block at that time... I figure one of those must have been the culprit.

 

Glad it's fixed. The old school trick does work, but it should not have shut the engine down with a dim light. I installed a gauge so I know that it's charging.