The Stovebolt Site Forums The Shop Area Engine Shop Flicker

I noticed coming in a bit ago I was getting a flicker in my dash and headlights that appeared like it was something induced by the ignition....

when I revved the engine it smoothed out and got more pronounced when it idled back down...

any suggestions? a strategically placed capacitor maybe? a failing diode or rectifier?
voltage regulator?

TIA

Florida,

Didn't mention what type of vehicle, engine type, generator/alternator, or whether you were working with 6 or 12 volt.

Might get a better diagnosis, if we knew what you were dealing with.

A normal generator? Failing diodes in alternator or bad connections to the battery or burned out charge lamp on the dash?

sorry bout the specs...it's 67 c-10 250 cid...

sorry to say I don't know if it's a gen or alt...

12v sys tho...still has points ign and I'm pretty sure there's what looks like a relatively new
Volt reg ...the points, condensor ,rotor cap, and plugs/ wires are all pretty new like a month or two...

I put a meter on the batt when running just the other day and read a bit over 14v about 12.8v turned off suggesting I had charging...

It sounds like you've got a diode out in the alternator. An alternator is a 3-phase AC generator, with 6 diodes to rectify the output to DC. One bad diode knocks out the winding it's attached to, plus another one because of the counter-voltage created. The one remaining leg still charges, but at less than 1/3 of rated amperage. it also causes a flicker at low speed.
Jerry

As usual Hot Rod is right on. You might try that voltage test again. Turn on the lights & heater & accelerate the engine. If it won,t come up to 14 volts than the alternator is weak. It possibly could be the points in the voltage regulator. A battery getting weak could cause that but I doubt it being it held 12.8 volts.

thanks guys...I'll get the meter back out...and see what output I have...I have no idea how old the battery is but based on appearance the VR looks shiney and pretty new...(I know...great diagnosis:)...and the alt/gen doesn't look orig either...

think a reman alt and new VR is the way to go?

The most accurate test is done with a high-rate ammeter, and enough load on the battery to put the alternator into full output, but that type of test equipment is usually only found at a professional shop. You can do a rough test by turning on all the accessories you can, like high fan on the heater, high beam headlights, cigarette lighter, etc., and look for a low output voltage, but it's hard to get enough load on a system for that to be a valid test. If in doubt, have a pro do a "full field" test on the alternator, and see if it can produce its rated current flow.
Jerry

Carquest has a regulator that looks & fits like the original but is all solid state. It has a very smooth voltage. I got a new reg. for my 71 Buick & was surprized how lightweight it was. Than I read the direction sheet & it told it was all solid state.

HRL, I have an amp probe (clip on induction type)
for ac current...I know dc current meters that read any significant dc current are rare except for usually industrial apps...
not sure if that would work and if it did not sure what amperage this alt/gen should be producing with a good load...also I have never even tried to crank the heater yet...not sure if it even works...got this truck in Fl july...and I noticed some work needs doing here...
at least I have noticed no leaks from the heater core...

this morn it was cool for us anyway...I guess it's time to be checking out the heat status..

Ok here we go..just put my meter on the battery engine running and off...meter is an Ideal...nice 100 dollar meter...

running w/ no extra loads reads 14.8...killed the eng and batt reads 13.2....running with brights,wipers,turn sigs ect batt reads 15.05! wth?...couldn't get my heater blower to work until I sent it a direct test feed from the batt...with the blower switch on reads hot at the feeder lead to the blower but plugged back in it won't run the blower?...there is all kinds of creative splicing/wiring under the dash...colored spagetti...DOH!...

this old truck has many issues...

For instance, the charging system tester/battery load tester I use in my shop has a 600 amp DC capacity! It uses an inductive current probe. The high range is used for load testing batteries. An average alternator from the 70's and 80's that's the most popular conversion for the old stovebolts will be anywhere from 55 amps to 80 amps at full output. One with a bad diode will usually have a max output of 15 amps or so, enough to keep the battery charged during daytime running, but not sufficient to carry headlights, heater, etc. without draining the battery. An alternator with a shorted diode will be noisy, and might be hotter to the touch than normal.
Jerry

Hmmmmm- - - - -
If it's producing that much voltage under load, it's doubtful there's much wrong with the alternator. Be sure the regulator base is grounded well, and the flickering might go away. I like to run a ground wire from one of the regulator mounting screws back to the alternator mount, or anywhere else on the engine, for that matter. Sometimes a flaky ground will do funny things to regulators. I remember one Dodge pickup that had normal charge voltage with the lights off, but went to over 16 volts as soon as the headlights were turned on. It seems that the regulator mounted on the firewall was finding a ground through the headlight filaments with the light switch off, but going full output as soon as the headlight current eliminated the ground path! A ground wire to the regulator base fixed that one.
Jerry

That,s too much voltage. If your ground is good like HRL posted you need to replace the regulator. They can be cleaned & adjusted but it,s a pretty delacate procedure.

Don't over look the head lamp dimmer switch. These things can run you nuts and can cause a flicker like you described.

ok...here we go again...I went back out pulled the VR...there is what looks like a capacitor
(just about like the one under the dist cap)
plugged into a connection on the back?this is obviously something a po did along the way as he spliced it to a female connector to make it fit on the vr male prong connector...I see the contacts that go to the connector plug going to the main wire harness...I made sure every ground I could see that was anywhere near the reg was sanded off and cleaned and added a new one to the frame..
here's a wrinkle..I started it back up after all this and I swear it read like a trickle charger....14.8 then momentary blips to 15.03 and back down again?when the motor was revved the voltage still stayed in these parameters?
gremlins...sheesh

wierd....I guess I need a new reg...I am going to see if all this did any good with the flicker as it gets darker outside...

Just back from the convenience store coffee run...

Flicker still there ... ...

guess I'm gonna have to change the VR eh?

I'd swap the regulator, preferrably for a solid-state one. The mechanical-contact regulators are prone to getting dirty points, and having other problems. Normal voltage against a fully-charged battery will be somewhere in the high 14's, maybe 14.7 or so. Current flow into the battery at full charge will be about 10 amps or slightly more. The capacitor has only one function, filtering out noise in an AM radio. The system will work just as well without it.
Jerry

Hey Fat Fenders


Pretty strange I noticed last night the flicker went away and stragely enough my hi beams indicator light doesn't work now and I know for a fact it was working when I had the flicker cause I turned it on and off after your post and it didn't seem to matter when I did but now the ind lite is gone and so is the flicker ???
co inky dink or were you on to something...?

I had a problem with my lights also. The head lights would not come on when I pulled the switch out. It truned out to be the dimmer switch was bad. Drove me nuts for a while until I talked to a friend that has been building hot rods for 35 years, that's what he told me to look for. Seems like he is a pretty smart guy.