A Little Electrical Help Please
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
A Little Electrical Help Please
My '72 has an electrical problem that causes the lights to dim briefly then go back to normal. When this happens, the volt gauge also drops to below zero then back to normal.
I first suspected the alternator so I took it in and had it tested this morning and it tested fine as did the internal regulator.
I then checked the connections on the battery and they are good and tight.
It doesn't make any difference whether the headlights are on or off, the stereo on or off, day or night.
I'm out of ideas so I'm hoping some of you may have resolved a similar problem that I can look into.
Thanks in advance.
cc
I first suspected the alternator so I took it in and had it tested this morning and it tested fine as did the internal regulator.
I then checked the connections on the battery and they are good and tight.
It doesn't make any difference whether the headlights are on or off, the stereo on or off, day or night.
I'm out of ideas so I'm hoping some of you may have resolved a similar problem that I can look into.
Thanks in advance.
cc
Burning Brakes
Joined: Jan 2007
Posts: 1,164
Likes: 1
From: Port Clinton Ohio
St. Jude Donor '08-'09-'10-'11-'12-'13
Fist thing I would check is where the negative battery cable attaches to the frame. Mine was bad and it caused all kinds of strange things to happen.
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
How is your drive belt on the alternator. I had the same type of problem and it turned out the belt seemed tight but just wasn't tight enough. Used a pry bar on alternator prior to tightening bolt and problem went away.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
cc
So, if it was a ground wire, I would suspect it is loose to account for the intermittent drain and draw enough voltage to affect the entire electrical system rather than one or two components.
Or one that is on a component that cycles on and off.
Last edited by CCrane65; Dec 2, 2009 at 01:23 PM.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Thanks.
Anyone else have any ideas?
Instructor
Joined: Nov 2006
Posts: 119
Likes: 2
From: Baton Rouge La
I hope this isn't your problem but when that happened to me the clip holding my positive battery cable came off. It drove and I even brought it in to a mechanic to have it checked and he was stumped. One day they flickered and the car killed. The cable ended up getting wrapped around my driveshaft or something and catching fire. No damage but lots of smoke (and fire department).
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Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I have more questions than answers.
You said the lights dim,what lights ,courtesy ?
Will this happen if the engine is not running, ammeter discharging then returning ?
Is your clock the old original type ? A clock rewinding can pull pretty hard.
Try pulling the courtesy light fuse and shut down that circuit and see if it still does it.
I doubt the short load test Autozone types do will bring out an intermittent problem.
If you have jumper cables use one of them to act as a secondary ground.Attach one end to neg batt term and other end to frame.
You said the lights dim,what lights ,courtesy ?
Will this happen if the engine is not running, ammeter discharging then returning ?
Is your clock the old original type ? A clock rewinding can pull pretty hard.
Try pulling the courtesy light fuse and shut down that circuit and see if it still does it.
I doubt the short load test Autozone types do will bring out an intermittent problem.
If you have jumper cables use one of them to act as a secondary ground.Attach one end to neg batt term and other end to frame.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I hope this isn't your problem but when that happened to me the clip holding my positive battery cable came off. It drove and I even brought it in to a mechanic to have it checked and he was stumped. One day they flickered and the car killed. The cable ended up getting wrapped around my driveshaft or something and catching fire. No damage but lots of smoke (and fire department).
I had one in the other day with 1/2 the clips missing. I probably wouldn't have noticed if it wasn't for the shiny ring on the driveshaft.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
It's going to take a day or two before I can try these and get the results posted. I found a quarter sized hole in the rear half of the alternator case just under the adjustment bolt ear. So tomorrow, my neighbor and I are going hunting for a case to replace the broken one.
At least the half with the numbers is in good shape. I plan to hunt with 2 things in mind, first look for an exact replacement rear piece and barring finding that get one that will work until I can locate the correct one.
cc
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
I hope this isn't your problem but when that happened to me the clip holding my positive battery cable came off. It drove and I even brought it in to a mechanic to have it checked and he was stumped. One day they flickered and the car killed. The cable ended up getting wrapped around my driveshaft or something and catching fire. No damage but lots of smoke (and fire department).
cc
Last edited by CCrane65; Dec 3, 2009 at 12:03 AM.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
I installed a reman. alternator this morning and then ran the car until it was at operating temperature. So far no more dimming or battery gauge drops below zero.
I have check everything you guys mentioned that I could do from above. I will put the car up on the left and check the rest.
Thanks again. I plan to wait until I get a job to restore my original alternator.
cc
BTW Roger, I think you are correct in that the machine at the parts stores are only godd for letting you know the alternator is in complete failure.
When I spun the pulley it sounds like the bearings are going so in addition to the intermittent electrical issue there is an impending mechanical issue.
I have check everything you guys mentioned that I could do from above. I will put the car up on the left and check the rest.
Thanks again. I plan to wait until I get a job to restore my original alternator.
cc
BTW Roger, I think you are correct in that the machine at the parts stores are only godd for letting you know the alternator is in complete failure.
When I spun the pulley it sounds like the bearings are going so in addition to the intermittent electrical issue there is an impending mechanical issue.
Last edited by CCrane65; Dec 3, 2009 at 02:48 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
To help diagnose your problem, you may want to hook up a voltmeter to one of the interior lights (courtesy light?) so that you can see if the voltage is changing [or not] when the lights dim. Your 'clue' about ALL of the lights dimming at the same time is informative...as all of them do not operate from the same ground point. Thus, if a single ground was the problem, only those on that ground should dim. It could be a main battery ground line problem, but you didn't indicate that any other electrical devices were giving you a similar problem (heater/vent fans, radio). With the voltmeter connected to the [+] line on the bulb (which has this dimming problem) and hook the [-] terminal directly to the negative post to a known good groud point..or to the negative post on the battery. When the lights are normal read the voltage; when the lights dim read the voltage.
My first impression is that the alternator voltage regulator is defective and that the local auto store couldn't detect it because they didn't load the output properly. But, it could be a bad connection on the battery ground wire.
My first impression is that the alternator voltage regulator is defective and that the local auto store couldn't detect it because they didn't load the output properly. But, it could be a bad connection on the battery ground wire.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
That's what I think also. Since I have the alternator off the car is their a bench test I can perform on it?
If not, I can take the reman out and put the original in for testing.
cc
It's getting dark now so I can go see what the lights do with the reman in the car.
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Just got back in from running the car in the dark and replacing the alternator really seems to have fixed the problem.
If it's possible the dash lights are brighter too. There was not even the slightest hint of lights dimming and the battery gauge needle was in positive territory the entire time at approximately 14. In fact, it barely moved at all.
cc
If it's possible the dash lights are brighter too. There was not even the slightest hint of lights dimming and the battery gauge needle was in positive territory the entire time at approximately 14. In fact, it barely moved at all.
cc