lights flicker at cruising rpms fine at idle?

-
T

taco502001

Well-Known Member
Joined
Nov 9, 2005
Messages
73
Reaction score
2
Ok I have 71 dodge demon with a 440....most recently I have changed the alternator (78 amp flat back), it has a newer voltage regulator on it....has new belt, cap and rotor and plugs.

today i was getting ready to hook up the new temperature gauge and got as far as it has the wiring for the lighting hooked up and ran out of time and daylight....I took the car for a drive then noticed that at idle my ammeter sits right in the middle everything is working great but when you go to accelerate or sit at say 2-3k rpms the car appeared to be overcharging and the needle bounced back and forth quite a bit at the +20 to +30 mark

I unhooked the wires to the new gauge and it settled down a little bit but was still bouncing a little bit but staying right around +20....did I mess something up, will it go away when i get the rest of the wires on the gauge?

I plan to check all my grounds tomorrow the best I can just wanted to make sure i did not mess anything up
 
I'm always preaching this, but I'd bet this is our old friend "the screwed up bulkhead connector" or other related problems causing voltage drop

Get the car running to simulate "low to medium cruise" that is, around 12-1500 RPM. Make some checks first with all loads off, and again with lights, heater on

What you are looking for is bad connections through the harness.

Stick one probe of your meter directly onto the neg. post of the battery, and the other directly onto the frame of the regulator. You are looking for a very low reading, the lower the better, and zero volts would be perfect. Anything over .2V (two tenths of a volt) is too much, and indicates that the ground between the regulator/ body/ ---engine block --battery is not good

If that is OK, make the next check, if not, improve the ground

Next, stab one probe of your meter directly onto the battery pos. post, and the other as close to the regulator IGN lead as you can get. The "dark blue" ignition run side of the ballast will do.

Here again, you want a really low reading, and over .2v is too much. This indicates a drop in the path from the battery, to the start relay stud, the fuse link, through the bulkhead connector, the ammeter, through the connector to the ignition switch, the switch contacts, back OUT the connector, back out (on the dark blue run wire) the bulkhead connector, and finally connecting to the regulator/ ignition system

Some other things to look for is open the hood with it charging IN THE DARK and see if there is a small lightning storm going on inside the alternator. This usually indicates physical damage, which has now caused the insulation to rub itself off the windings.

Also check one probe on the alternator output stud and the other probe on the battery. Look for the meter "jumping around." If it does, you probably have a bad connection that is arcing, sparking, making, and breaking.

To see if it is in the field circuit or the main charging lead, Find the GREEN wire on one of the two push-on connections at the alternator and remove it.

Clip the exposed terminal to ground

Now "rig" a good clip lead from the battery directly to the OTHER "push on" terminal of the alternator

You have just created a "full field" situation

Start the engine, and GENTLY play with the throttle, watching the ammter. Experiment with the headlights, heater, on/ off and look for "jumping" at the meter.

If none, the problem is in the field circuit wiring of the regulator

If it still jumps, it is PROBABLY either in the main charging lead --from the alternator, through the bulkhead, to and through the ammeter, back out the bulkhead, to the battery

OR it just might be a problem in the alternator itself. This could include just about anything in the alternator, so you might try a known good working one.
 
Usually flickering or pulsating lights are caused by a diode on the rectifier plate being bad another thing that makes the lights flicker is a brush bouncng in the brush holder. We have a saying around the shop... "Just because it's new doesn't mean it's good!" a third thing to do this is a short in the secondary windings of the stator. I would take the alt back and have it replaced and go from there
 
yeah i just find it odd with lights and heater on and in drive it is perfect at idle....just acts up when driving.....but I will try all those tests you have posted tomorrow and go through all my connections and make sure everything is clean and tight and go from there at least alternator has warranty so free replacement there
 
Your remark about the alternator warranty suggests you are running a "remanufactured" alternator from a parts store. They're usually junk that works poorly no matter how many times they get replaced free of charge (as it were). You can get a new (not "remanufactured") one from Old Car Parts Northwest.

Make sure the alternator, regulator, and battery are all bonded on the same ground plane. Run a new 14ga wire from the "GRD" hole on the back of the alternator housing to the voltage regulator base, and from the voltage regulator base to the battery negative terminal. See here and here.
 
Can be the voltage regulator too, even though its nearly new.
That was the cause of my bouncing needle.
Always disconnect the battery, install components so they are chassis grounded before connecting .
 
yes i installed a brand new re manufactured alternator....I noticed quick glance that engine is not grounded very well i believe just the one from battery to block....also it mainly really acted up badly after i hooked up the wiring to the new gauge
 
ok update ground was loose on back of alternator and is now tightened down, i am trying to systematically go through things here....I also noticed my bulkhead connectors are no longer on the firewall but inside the frigging car under dash now
 
Do you mean that someone changed the connector, or it just fell out of the firewall?

Check these out carefully for damage.
 
no somehow the bulkhead connectors fell out into the car....I checked them cleaned them and the wires and everything look perfect

I tested voltage at battery with car running and am getting a consistent 13.5-13.6 volts and at highest fluctuation when i turn everything on and full draw of heater, radio, lights etc.... dropped to 13 volts and highest with everything off and car first started 14.0 volts at idle....I also performed the first two tests you mentioned and got a reading of .02 volts


I do only have the battery to engine ground no others, voltage regulator bolts are stripped but being held in pretty solid
 
slantsixdan said:
Your remark about the alternator warranty suggests you are running a "remanufactured" alternator from a parts store. They're usually junk that works poorly no matter how many times they get replaced free of charge (as it were). You can get a new (not "remanufactured") one from Old Car Parts Northwest.

Make sure the alternator, regulator, and battery are all bonded on the same ground plane. Run a new 14ga wire from the "GRD" hole on the back of the alternator housing to the voltage regulator base, and from the voltage regulator base to the battery negative terminal. See here and here.
Click to expand...

I have to agree with Dan on this one. I had a bad alternator that was causing flickering while running down the road. It was a "remanufactured" alternator and was junk. I replaced it with an older one I had lying around (not as pretty) and it worked fine.
 
You must log in or register to reply here.
-

Back
Top