I have a 84 and when I am at idle the dash readouts tend to flicker when I am at crusing speed it does not seem as bad. Any ideas on what it is?

 

Low battery voltage will contribute to flickering. When your engine is idling and you have a heavy electrical load, the alternator cannot deliver its rated current at this low rpm and the battery picks up the load which causes the voltage to fall below 13 v, but when you get underway, rpm picks up and the alternator provides all the load current and charges the battery and the voltage will be above 13 volts.

 

Battery was new last year. Alternator read out says it is putting out between 14-15 volts all the time. Could the voltage reg. be going bad?

 

Mine does the same...and my battery reads high 14.5-15.doesnt bug me that much but I was woncering as well what it could be :confused:

 

Mine does the same thing...Anyone have any ideas?

 

Can I join this club? My 85 does the exact same thing! It's putting out about 14.2 volts, but ALL of my lights flicker slightly when I'm at idle/low speed. When I speed up, it goes away. The battery is only a few months old. It beats the heck out of me! :confused:

 

Assuming none of you have different pulleys on the engine........ you may want to have the alternator load tested. That is see if it's putting out the AMPS it's supposed to, when Mine did that years ago it turned out to be a battery dying and the alt was putting out plenty of juice. How about dirty terminals?........ or bad connections at the alt?........ last but not least how about loose connections in the dash......... god forbid......... but it's not THAT bad....... :seeya

 

Providing your battery connections are clean the the alternator is bad. Mine was putting out 14-15 volts and all of the lights were flickering. I noticed the dash first, then when I had to drive at night the headlights flickered at idle. 14-15 volts is not normal. Once I replaced the alternator, it went back down to 13-14 volts and the flickering stopped.



[Modified by Grzldvt, 8:01 PM 11/4/2002]

 

Grzldvt - You had exactly the same symptoms that I'm having. I know for sure the battery connections are clean; I cleaned them when I replaced the battery this spring. How did you find out that 14-15 volts is not correct? I'm not disputing it, I just want to learn more about it. Did you change the alternator yourself? I've heard it's not difficult, but that they are very expensive. Thanks again! :seeya

 

I have seen the alternator voltage regulator oscillate causing the lights to flicker. If you look at the waveform across the battery when the lights flicker, you can see the oscillation on an oscilloscope. You can replace the voltage regulator or the alternator.

 

jfb - Is the voltage regulator a part of the alternator or can it be replaced separately? Is it something a novice could do? Thanks for your input!

 

bad rectifier in the alternator, replace rectifier module. kitt

 

SwampRat,
My alternator was a rebuilt, done by a local rebuilder. Since I installed it last February, the alternator only put out 13-14. I started flickering and was putting 14-15. I checked with the rebuilder, and he told me it was too high. I took the alternator back to him and he checked it.... He told me it was bad. Fortunately, I had a 3 year warranty, so I got a free replacement. The warranty started all over again with the replacement.

For installing a new one, it took me less than 10 minutes tops to pull the old and less than 10 minutes to put the new one in. It is not complicated at all. The hardest part is lining up the bottom bolt. If you have metric sockets, a 10mm open end wrench, you have the tools to take it off.
It is held in with 3 bolts, and I loosen the bolt that allows the air pump bracket to swing up and out of the way.
I paid $175 for my rebuilt and kept the core.

As far as rebuilding or fixing. I have my original alternator, and it was working, but the bearing was going bad, based on the noise it was making. I followed the instructions on the Tech tips.... no way will the shaft come off of the housing without a press. Trust me I have tried, to the point I have mangled the threads on the shaft.
I can get to everything else, but the bearing, so I replaced.



[Modified by Grzldvt, 8:41 PM 11/5/2002]

 

Grzldvt - Thanks for the info! :)

 

One thing to check for is a bad ground on the transmission. Many times after a tranny has been pulled out, the bellhousing bolt on the drivers side, I think the second one up, comes loose and that is where the dash is grounded. This has happend to me on more than one C4. It is something free to check. Look at the tranny bellhousing bolts, and you will see which one has wires grounded to it.
Shawn

 

I was ignoring my slight flickering until my last trip back from New York. The dash started flaring brightly on the Turnpike, and I noticed that the red block would light next to the temp/volts indicator, and the high reading would display (16.4+ volts) even though I had the temp displayed! Thius happened about every 3-4 minutes for about 2 seconds each time. The next day I saw 17.5 volts! I called the previous owner who said the relatively new alternator had a lifetime warranty, so we changed it - both were new. Ten minutes after the change, the slight flickering started again! We saw a little corrosion around the bottom of the battery during the operation, so I slept on that. This evening I pulled the battery and the battery tray and :U what a MESS!! Acid corrosion everywhere!! The battery ground and engine ground strap are in the middle of the mess, and the quality of the connections HAS to be effected. I've sprayed everything down with baking soda and now I'm looking at the mess on my hands (wear gloves!)

In short, check for any signs of corrosion. If the ground connections aren't spotless, pull the battery and tray - you might save your frame! Good luck.

Ray

 

Had the same problem with my 85 Vette. Replaced the battery but it still did it. It got worse and flickered (shimmered) almost all the time (driving or idle). Finally replaced the alternator and the problem went away. Pretty sure it was the alternator.

Hope that helps

 

I too have 14.3 - 14.5 constantly on my '96. I don't notice the flickering so much, but I do notice that the turn signal at idle makes the voltage guage drop and recover almost as if the battery were not good. I had the alt checked by Cheverolet AND another auto parts place and both say its fine. The parts place also said a load test on the battery showed good. I am convinced the battery is bad, but I have no evidence../shrug , whats a man to do? ; )

 

I would take tha alternator to a real rebuilder/electrical place. Generally these guys no more than your basic auto parts guys. On the flip side, eventually something will fail and then you will know :mad