Ok, first, watch this. I took this video last night.

http://www.youtube.com/watch?v=vDrP_...ature=youtu.be

I drove into my work lot yesterday and the car went into emergency mode and damn near shut down. Turns out the bolt that screws into the side post of the battery was messed up, wasnt getting good contact, I fixed that issue and the car runs like it did.

Now this has been going on for a little bit but in that video the lights and everything dim and go back to full like the voltage is fluctuating or something. If you watch the voltage gauge it doesnt budge. The alternator is charging as it should and the battery is a good optima that charges well and runs great.

What could this be? I did some research and im pretty sure its the voltage regulator in the alternator. If it is ill just get another alternator but the car runs just fine, zero problems. Its just anoying as hell when you drive at night and the lights dim like that.. BAH! One more thing! (actually my vette has had minimal issues, been happy as hell) Also, this 98 C5 has 60k miles on it, not abused. Thanks!

Joe

 

If your voltage does not fluctuate but the lights dim it would seem your alternator is working fine. It seems like you have a loose wiring connection, bad Multifunction Switch, faulty headlight Relay Switch, or poor ground connection. Not at home now but if not one else chimes in I can post the wiring schematic for you. I can't tell from the video if it is one light or both. Also, does it do it for low and high beams? That info would help. Should not be hard to figure out.

If I remember you should also be able to turn the lights on "without" the engine running and see if you get the same results. It would provide some more data to go on.

 

It was both lights, it seems like all of the electrical power does it all at once too. When the car is running like at 55 it doesnt do this, when you let off the gas as the rpms drop, it starts for a second until you accelerate more.

Im gonna try that tonight with the engine off. Also if you listen, you can hear the fluctuation through the speakers if im not mistaken (light whine as the lights dim). The rpms are constant, no variation.

 

Did you try it with the engine off? I forgot the voltage gauge (like other analog gauges) use voltage limiters to keep the needles steady regardless of small alternator output changes. It would be nice to monitor the actual battery voltage at the battery when the lights do their thing. I can post the wiring schematic if you need it.

 

I tried it with the engine off and it does not fluctuate. Im gonna break out the voltmeter this afternoon and see what the voltage does. I did a quick test of it when i redid the battery terminal connector and the alternator was charging at the proper level.

 

In my opinion that means it is either something related to the charging circuit or it is vibration induced (which I doubt but can't refute yet). Here is a copy of the charging circuit. I am not concerned with the level of voltage when the car is running with the lights on, but rather if you see a fluctuation/change in voltage for a steady rpm. If you need help, I would prefer to discuss on the phone since it is so much easier. You can PM me with your number if needed.

 

Well, been working a lot, so not had much time, but I took the time and the voltmeter and did some tests on my vette.

When it first starts it doesnt have the issue at all, runs perfect. After warmed up it starts and when i got home tonight it started again, very noticeable.

Voltage is jumping, the guage on the car doesnt show it hardly at all but it goes from 14.22 volts to 12.45 and does this about once every 3 to 4 seconds. Now... you can hear something clicking in the front left side of the vehicle under the headlight area somewhere. Its not coming from the alternator. This is a video i took tonight.

http://www.youtube.com/watch?v=dGa_E...ature=youtu.be

 

Does it do the same thing with Low or High beams on? Also clarify if other lights are affected or is it just the headlights. That is important.

Also, did you have this issue before the battery terminal problem?

 

All the lights dim some what, high or low, the headlights dim more than the rest, did this before fixing the battery terminal. The voltage to the battery goes from the 14.22 to 12.45 as said above when i used a voltmeter on the battery terminals while the car was idling.

 

OK, it sure sounds like you have a charging issue that is aggravated with the extra load of the headlights.

Do this:
Check all the connections in the above schematic to make sure they are tight and not corroded. Do not forget to check the grounds. I helped someone a while back with a similar issue and it was actually the large alternator wire at the starter. It was pulled out and loose at the lug connection. He put on a new lug and all was fixed. Not at home to help you ID the ground locations. Can do that later or you can do a Goggle search to easily find that info on the Forum. I find that is easier that directly searching the Forum.

If you don't find a problem in doing that I have some other ideas we can investigate. Also please post whether your alternator has a decoupler. Should not be too difficult to figure out. Mr. Sam

PS: Forgot to ask if you see this problem if you are not at idle, like driving at 30mph or higher.

 

Never happens over 30 mph, only when you are slowing down, let off the gas as you slow down at lower speeds, or when its at idle. Ill google that stuff and look it over tonight, really sucks how dark it gets this time of year, working till 5:30 then you get home.. its already night time. lol

 

So... I took the time and checked my grounds and they all were in perfect condition, no corrosion or anything. I turned the car back on and listened to it some more, but its louder now for some reason, but ive figured out what this is. It is not the lights, the noise im hearing is the AIR pump under the front right light. It is turning on and off every 10 seconds or so which is causing the voltage drop.

Now.... why the crap is it doing this? Its obviously working but it cuts off after running for a split second. Could this be caused by a battery?

Thanks again,

Joe

 

The air pump is on the driver's side below the headlight so let's hope we are talking about the same thing.
Assuming we are for the time being, try pulling fuse 50 for the air pump motor in the engine compartment fuse box. If that fixes the lighting problem then we need to figure out if the motor is bad or if it is being cycled unnecessarily.

PS: Pull your codes now that we have a possible issue with the pump. That info, if it exists, could help with further diagnostics.

Here is a link you should read about the air pump ;

http://forums.corvetteforum.com/c5-t...tion-pump.html

 

Lights in my 02Z dim at times while driving all so. Not as bad as what yours are, but still bothersome. Going to check all the things dadaroo suggested. Thanks for posting this.

 

OP: Have you done this, or have you only checked grounds???

I think this could be a very distinct possibility here too.

 

If you don't find your problem with what we have discussed here so far, please create a new Thread and give us a link here to it, It can get too confusing with more than one problem in following what has or has not been done. I will be glad to work with you Lt Dan.

 

Im sorry i ment the front left side. It is the Air pump. I drove my vehicle this morning and the pump kicked on when i started the car like its supposed to it ran for a min or two then cut off. Car ran fine to work, no voltage drops from it kicking on, when i got to work i let it idle and listened to the car and watched the voltage gauge and it did not kick on the pump at all.

It usually does this in the afternoon when i return home when the temps are warmer outside. It seems to me the pump works fine, as it was working good this morning then cut off like its supposed to, its very spastic when it decides to start kicking on every 10 seconds.

I just checked the car for codes and i only had one. P1518 Chevrolet - Throttle Actuator Control Module Performance

I dont have a check engine light on at all, and the car runs great.

I do believe that the code above is because of my battery now that i think about it and did some research. I have an optima battery but its not been as strong lately as it should be bout 4 years old. Now.. could a low battery cause the air pump to freak out?

Another update, checked the battery and it was at 11.26 volts, im charging it right now with a 20 amp charge. Might be on its last leg! lol.. Be great if a low battery caused these problems, cheap fix! (i hope.. lol)

 

Clear the code and see if it comes back. If the pump starts cycling again it might be the PCM but lets not assume that yet. A number of people have deleted the air pump. I would do that probably before replacing a PCM (assuming we diagnosis it as bad).

 

Well, i decided to just go get a new battery, I had an optima with 800 cca 78, and It was about 4 to 5 years old, it was time. Ive had issues with that battery before with it acting weird with the positive terminal on it, so i went with a different battery, got a Duralast Gold same amps. After putting it in I had to finish up work but i drove it back home.


Not a single time did the Air pump come on, no voltage drops, no nothing, damn car ran like it did when it was new.

Of course, i shall see if that was the true fix for it after driving it some more but it drove without any problems at all after coming home.

And.. it also started up way better too.. AMAZING.. lol! *crosses fingers*