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Discussion Starter #1
This has been a problem for as long as I can remember. I don't know if I'm just used to it now or not, but either way, can't really tell if it is getting worse. When my car is idle my headlights and dome will flicker almost in unison with the loud tumble flaps (and engine noise I can't figure out). Again, this has been going on for a long time.

Now I'm sick of it. I want to do what I can to fix it. I've read that it can be a few things:

- bad/corroded grounds
- alternator wiring harness
- corroded battery terminals

Here are my question(s):

- Where are the grounds located in the engine bay that I should check?
- How can I check to see if my alternator wiring harness is bad or not and how to replace? (how-to here has pics that are broken links)
- Anything else that I should check?

My alternator went bad just after year 5 of owning the car (3 yrs ago). So I had it replaced with a new one (and battery too). I'm hoping that it is merely a bad grounding issue that I can clean up myself. I'd hope that the mechanic who installed the alternator would have seen a faulty harness. But that is wishful thinking. From what I've seen, the wiring harness is difficult to get to and do I know exactly what I would need to do to replace it. So any helpful advice is appreciated.

I have a meter to check grounds, so that is not a problem.

Thanks everyone. I can't wait to dish out rep points! [twothumbs]
 

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Start with voltage measurements, at the battery of course but also somewhere like the power outlet to see what's getting to the interior. (running, with the lights on, when you see the issue)

Do the battery terminals of course, but when they're off for cleaning follow the wires back to their connections - particularly the body ground from the battery & disassemble/clean them as well.

That's a good start, see what you find with that & go further based on what you find if necessary.
 

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Alt itself can do it by worn brushes or brush rings worn like these do so badly.
 

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Discussion Starter #4
amc49,

Is it common for foci alternators to go so prematurely, if 3-5 years is premature for an alternator?

I honestly can't remember it ever NOT flickering even the slightest.

Thanks

And thanks sailor for the tips. I'll keep that in mind. I hope to do some grounding checks this weekend.
 

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Check the wires under umbilical that goes from the trunk to the body for any cracked wires.
 

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Discussion Starter #6
Can someone tell me what I should be reading in voltage at the battery when the headlamps are on and the car is at idle? I plan on checking this when I get home. I'll also try to check grounds.

Great tip for the trunk harness, freemind. I didn't think of that. Thanks.
 

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ROUTINE VOLTAGE CHECKS:
- Check resting battery voltage, optimal is >= 12.6 Volts
- Check charging voltage 13.5-14.5 Volts with all accessories on and engine at at 1200 RPM
- Check cranking voltage (>= 9.6 volts)
- Check voltage drop across positive & negative battery cables. (<= 10 millivolts)
- Inspect connections all battery cables.
 

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Discussion Starter #8
ROUTINE VOLTAGE CHECKS:
- Check resting battery voltage, optimal is >= 12.6 Volts
- Check charging voltage 13.5-14.5 Volts with all accessories on and engine at at 1200 RPM
- Check cranking voltage (>= 9.6 volts)
- Check voltage drop across positive & negative battery cables. (<= 10 millivolts)
- Inspect connections all battery cables.
Thanks a lot!

What is the best way to check crank voltage? Also, my car does not have a tach gauge in the cluster. So can I just push the gas down a little to achieve the same effect?

Thanks again, rep point your way!
 

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Discussion Starter #9
I'm at work and did a quick check on battery voltage and grounds.

Now I haven't had much time to toy with things after work due to school, which is why it is taking me so long to check voltages and grounds. But when I just checked now, my battery voltage while resting was 12.64V. The grounds I've checked so far appear to have good continuity from battery to the grounds (two near battery and two on passenger side). I could not find any other locations where ground wires were located. But when checking any part of the frame with ground I appear to be good. Looking in the trunk, I cannot check for any shorts since the rubber sleeve over the harness is perfectly in tact. I'm afraid to remove the sleeve where it mounts to the inside of the door and the trunk ledge. But going underneath the trunk carpet, above the wheel well, I see no issues.

Since I'm by myself, I am unable to do other voltage checks with car on and crank voltage. But right now I am planning on going to advanceauto on my way home and have them help me check my battery and alternator.

Any other suggestions? I'd really be happy to fix this. The flickering is appearing to get worse. I'm not sure if it is because I'm paying more attention to it now or not. But on my way home from school last night, I could definitely see the flickering headlights on the back of the cars in front of me at lights. Revving the engine (car in neutral) stops all flickering. I really hope it isn't my alternator. I already need to get a new intake manifold because it is really bad at idle due to the tumble flaps. I feel like my car is going to stall sometimes when idle.

Thanks guys.
 

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Discussion Starter #10
So, i stopped at the auto store and had my battery checked. He said everything looked good and alternator was charging my battery. But he did say that it was showing that the battery needed a little charge.

My grounds, the four that I found, are good but I plan on cleaning them up along with the battery terminals this weekend.

Here is a dumb question. Please don't shoot me for asking. But my intake manifold needs replaced, badly. The tumble flaps make the engine shake horribly when idle. Is it possible that this is affecting my car in whole? It feels like could stall at times. Would that affect the lights?

Again, just spit balling here. I'm asking you guys since you are all a lot more knowledgeable than I.
 

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Rough, low idle - almost to stall - that would give you a flicker of the lights as the alt can't do it's thing at low rpm.

Flicker matching the rough running would point straight to that guess.

The 12.64 for the battery was a perfect "off" voltage BTW. You could hook the meter to anything inside, or use the odo trick for voltage, to see if it's dropping when idle is low & lights flicker.
 

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Discussion Starter #12
Honestly, when I'm sitting idle in traffic, the headlights flicker in unison with engine shake and tumble flaps.
 

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If you do have something effecting your idle speed, as sailor said points right to your issue if they are occurring at the same time. I had a similar issue with a sluggish IAC on my vehicle till recently (was working, but due to alot of gunk buildup it wasn't adjusting correctly), would cause engine to stumble and everything connected to the engine was effected (ie the power supply to the lights).


In short, yes, the engine stumble and the light flicker are linked. When the engine stumbles, the Alternator goes slower as well which in turn effects the power output, resulting in the flickering.
 
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