Just a quick question to get some ideas incase im missing something.
Car = 1998 civic 4dr LX
When I hit my breaks my headlights flicker off and on for a split second, and my stereo (head unit) turns off then back on again...

The headlights and dash lights have flickered when I hit the breaks for well over a year, I figured it was because the alternator is the original from the factory, and may be getting weak but it is still putting out 14.5V.
The head unit just started turning off when I hit the breaks in the past 3 weeks. I have spent a bit of time on the weekends trying to figure out why.

Head unit is an Alpine CDA-9874 (incase that info is needed), I had the head unit for about 5 years with no issues at all.

1 - I have checked all grounds in the cabin and under the hood and all are ok.
2 - I have checked all wiring to the head unit (uses adapter plug to the stock harness)
3 - checked all fuses - all good and none are loose.
4 - checked for any wires being affected by the break pedal assembly... none - all wiring under dash is stock and nothing is touching the pedal assembly...

Could this be related to the break switch? a relay gone bad?
Any other ideas on what to check for? this is getting really annoying...

 

I'm getting very frustrated with this issue. It seems to be getting worse as well. Now when I turn on the turn signals, or high beams the radio cuts out and lights flicker off then on...

Any ideas would be helpful....

 

It's no laughing matter, man.

Your alternator is almost surely kaput.

Redo this^ test with the high beams on, cabin blower on max, and the engine idling. What's voltage across the battery posts?

 

Check the taillight ground in the trunk area, it's either on the rear shelf or behind the trunk plastics.

 

LOL...
Will try that this weekend.

I will check that as well.

Thanks for the suggestions, I'll post back with results this weekend...

 

Ok, so far I have checked the voltage again as Ron suggested.
First voltage test mentioned in the first post was a cheap HF volt meter, this second test I borrowed my Dad's decent quality multi-meter.

Results are:

Engine off = 12.67
Engine on = 14.04
Engine on + high beams and heater fan = 13.53

I will be checking grounds in the trunk later.

 

voltages seem ok. alittle low if you ask me but not bad
Does the memory of the radio reset everytime this happens??

Definitely check the grounds and i know you checked the fuses but check the wires going to the fuses

 

Do you still have your original stereo to see if it is something with the new one? You mentioned the old head was fine, right? It's a long shot, but may be unrelated to the dash lights, or just more sensitive.

 

Checked ground in the trunk (near 3rd break light) and it was good.

drkyle - I don't have the original head unit. The current head unit is about 5 years old.

 

I believe there is another ground under the hood for the exterior lights, it's either on the driver or passenger side bolted to the frame below the fenders, maybe by the washer tank I think?

 

On each side of the headlight there is a white box that has all the grounds running to it. Make sure they are in nice and tight.

 

UPDATE:

After a month of chasing my tail on this issue, I think I finally found my problem.
I ended up pulling the dash harness out and checking every connection and every wire for shorts without finding anything. I checked and re checked all grounds and still could not find any issues.

I think I found the cause when I was replacing the oil pan gasket, the old gasket was leaking oil and it completely coated my alternator with oil.
I pulled the alternator out and disassembled it, cleaned all the oil out of it and re assembled and now the problem seems to be gone.
It appears the alternator had so much oil in it that it wasn't producing enough voltage to keep everything operating. I will know for sure after a few weeks of driving...

Thanks again to all those who gave suggestions...

 

I would check the turn signal switch replaced that on dash lights and tail lights going dark randomly. This fixed the issue for dash and tail lights.

 

Actually the update above your post was 1 of a few problems that I found that fixed the issues I had.
#1 - alternator was full of oil, after being cleaned seemed to be ok... then it started again...

#2 - connector for + battery terminal was loose and corroded inside... the wires were not making good contact. Replaced both + and - with new terminal connectors and seemed to be ok... then it started again...

#3 - found out the battery was cracked and had no fluid inside. It must have been dry for a long time since I never saw any evidence of a leak this entire time until I filled with DI water and it leaked out within a day.
that's when I saw the crack on the bottom of the battery and the corrosion on the battery tray... replaced battery, 3 weeks with no issues and i'm confident I finally fixed the problem.

 

One thing I still cant understand is how did the battery work for this whole time without any fluid inside?????
When I put the DI water in, I could see a lot of corrosion inside and it was bone dry...
It would explain why the car would be very hard to start...