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Old 12-06-2010, 09:41 AM   #1
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Stuborn Electrical Problem '02 Boxster

I am new to this site and have used much of everyone's helpful posts to work on my friend's 2002 boxster. It seems that there continues to be a stuborn electrical problem that I can't figure out and thought someone out there may have experienced this. The battery kept dying (6 yrs old) so I replaced the battery. The dealer confirmed that the alternator was bad so I replaced the alternator (and serpendine belt at the same time). Not difficult with the help of this forum. However, the car still has a problem with all of the lights continuing to flicker lightly (headlights, interior lights, LEDs on stereo etc.). I am not that familiar with boxsters and someone suggested it might be a "boxster thing" but this doesn't sit well with me. In addition the front speakers cut in and out when accelerating. I thought maybe the channel related to the front speakers in the stereo unit was going bad, but it only does this when the engine is on. When it is off, and using just the battery, the stereo/CD works fine. About a year ago the dealer replaced the ignition for my friend - could this have anything to do with it? Although 8 years old, this car has less than 25,000 miles on it.

Does anyone have any thoughts on what else this could be? All thoughts are welcome.

PB2002
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Old 12-06-2010, 10:30 AM   #2
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check the usual suspects...connections,grounds etc. expensive electrical test equiptment would help. is ANYTHING else acting funny...if so maybe ignition switch again
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Old 12-06-2010, 03:56 PM   #3
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Before spending any more money - heres a very quick back to basics guide...
You have already installed a new battery & alternator. Flickering can be caused by a bad ground (there are several) and pulsating from the alternator is usually absorbed by the battery.
Do you have a multimeter - if so, heres a rough & ready check list - voltage values are approx:

1) Check your battery terminal voltage without engine running - should read approx 12.6 volts - if lower than that charge it for ~12 hrs and check voltage again.

2) Read alternator output across the battery terminals with engine running - should be 13.5 - 14.5 volts - if not in this range, a more specific load test must be performed with specialist instrument to check alternator.

3) Inspect the ground cable @ the battery and where it bolts onto the chassis.

4) Run a temporary earth (ground) wire from the (-) side of battery & connect to a suitable bolt or part of the engine and see if the problem persists - this will check if you have a broken or high resistance earth in the system.

The above is a very simple check - if the problem persists, it could be a very time consuming exercise without (as extanker says) expensive test equipment.
JFP in PA might be able to shed a bit of light as he has seen a couple of electrical issues in his time....
Hope this helps......
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2001 MV Agusta F4.

Last edited by Steve Tinker; 12-06-2010 at 04:00 PM.
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Old 12-06-2010, 04:15 PM   #4
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Quote:
Originally Posted by extanker
check the usual suspects...connections,grounds etc. expensive electrical test equiptment would help. is ANYTHING else acting funny...if so maybe ignition switch again
Just the flickering lights and the stereo cutting in an out. I will have to check into the ground wires. She brought the car out from NY to CA, so maybe the weather back there got to something over the last 8 years.
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Old 12-06-2010, 04:32 PM   #5
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Quote:
Originally Posted by Steve Tinker
Before spending any more money - heres a very quick back to basics guide...
You have already installed a new battery & alternator. Flickering can be caused by a bad ground (there are several) and pulsating from the alternator is usually absorbed by the battery.
Do you have a multimeter - if so, heres a rough & ready check list - voltage values are approx:

1) Check your battery terminal voltage without engine running - should read approx 12.6 volts - if lower than that charge it for ~12 hrs and check voltage again.

2) Read alternator output across the battery terminals with engine running - should be 13.5 - 14.5 volts - if not in this range, a more specific load test must be performed with specialist instrument to check alternator.

3) Inspect the ground cable @ the battery and where it bolts onto the chassis.

4) Run a temporary earth (ground) wire from the (-) side of battery & connect to a suitable bolt or part of the engine and see if the problem persists - this will check if you have a broken or high resistance earth in the system.

The above is a very simple check - if the problem persists, it could be a very time consuming exercise without (as extanker says) expensive test equipment.
JFP in PA might be able to shed a bit of light as he has seen a couple of electrical issues in his time....
Hope this helps......

Steve:

This is very helpful. I do have a multimeter (confirmed the alt was bad before buying new) so I can give you a response to a few of your items:

1. The voltage from the battery is exactly 12.6 volts.

2. A test on the voltmeter of the terminals with the engine running reads 13.1 volts. At engine start it is a little bit higher, but never gets near 14 volts. This is a 120 AMP remanufactured Bosch alternator (supposedly the OEM one) that I got from ******************************** a week ago (in fact I still have to send them the old core). Seems like a low probably that they sent me a bad one. Could something else be draining the power away or is 13.1 volts enough to keep the battery charged?

3. Ground cable at the battery is clean, made sure when I replaced the battery. I will have to find where it connects to the frame, check it and report back?

4. I will run a temp ground and see if this eliminates the problem and let you know.

This has been very helpful.
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Old 12-07-2010, 12:38 AM   #6
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PB - the alternator voltage does seem a low @ 13.1 v. What does the voltage go up to when you increase the engine revs?
When I installed my underspeed pulley (which actually runs the alternator at a lower speed) I was getting 14.1 v @ 750rpm and 14.5 v @ 1250 rpm.
Your initial low voltage could be a faulty alternator, or a high resistance ground.
To really know the answer to a faulty alternator you need to load test it - most auto-electrical places (preferably Bosch agents) will be able to do this.
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Old 12-08-2010, 10:55 AM   #7
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Steve:

The voltage increases 0.20 volts to about 13.3 when the engine is revs, I would have thought it to be higher. I set up a separate ground to another bolt on the frame and this did not make much difference, in fact the voltage actually dropped abit into the 12.8 volt range. I clean the ground wire to the battery terminal again and where it is bolted to the frame (about 10 inches away), both places showed no signs of corrosion.

I am a bit shocked if the alternator is bad as I just purchased it and installed it last week. I will see if I can find someone that can load test it before I yank it out and send it back. Please let me know if anything else comes to mind.

I will let you know where I come out on this....

PB2002



Quote:
Originally Posted by Steve Tinker
PB - the alternator voltage does seem a low @ 13.1 v. What does the voltage go up to when you increase the engine revs?
When I installed my underspeed pulley (which actually runs the alternator at a lower speed) I was getting 14.1 v @ 750rpm and 14.5 v @ 1250 rpm.
Your initial low voltage could be a faulty alternator, or a high resistance ground.
To really know the answer to a faulty alternator you need to load test it - most auto-electrical places (preferably Bosch agents) will be able to do this.
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Old 12-08-2010, 01:10 PM   #8
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On the face of it, it certainly looks like an alternator problem - barely 13 volts with no load seems low.
I wonder what the v reading is if you leave the engine running, switch on all the lights, fans, A/C etc and then read the battery voltage again. I wouldn't be surprised if its even lower - maybe even drawing current from the battery ....
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Old 12-09-2010, 07:34 AM   #9
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Steve:

You are correct. When you turn on the lights, A/C radio etc. with the engine running the voltage drops into the 12.6 - 12.8 range. I am going to replace the alternator again under warranty and see if this solves the problem.


By any chance do you happen to know what function / system the plug on the alternator serves? There are three wires on the alternator. The thick cable and red wire (with the eye connector) that is bolted to the back. The other wire (blue) is terminated with the black mercedes benz connector which plugs into the back of the alternator. It travels back into a wiring harness. Do you know what this wire supports or what its function is related to the alternator?

PB
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Old 12-09-2010, 03:47 PM   #10
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I think the wires that eminate from the connector are for the charge warning light and field energising circuit. They will be control / indicator circuits though.
I could be wrong - its been known before....
One thing I did forget to mention is that the battery must be fully charged when you check the alternator output voltages - a half charged battery can give all sorts of strange numbers. Charge for at least 12 hours and test as mentioned.....
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2001 MV Agusta F4.

Last edited by Steve Tinker; 12-09-2010 at 03:54 PM.
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Old 12-09-2010, 07:46 PM   #11
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I thought the connector wire might be the warning light. Just wanted to get your thoughts on whether is was sending some type of instructions to the alternator, but I suppose all of the "brains" that control output voltage are in the alternator. I will recharge the battery again and do my tests. I am taking the car to the dealer next week to have them test the ignition switch again. As one of our earlier members suggested, the switch they replaced in June might have failed. Stay tuned....
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Old 12-27-2010, 12:17 PM   #12
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Stubborn electrical problem - RESOLVED

Steve:

Just wanted to close the loop on this thread...I took the car to the dealer and they tested the ignition switch and confirmed it was not the problem. They then wanted to charge me $200 to begin testing the wiring to find where the problem was coming from. I decided to give it a shot myself. When I got home, the new "replacement" alternator had arrrived so I swapped out the one I put in a week ago and Voila! The voltage test put it at 14.2 volts, just where you thought it should be...

However, the lights continued to flicker and the stereo still cut in and out. I then removed the Positive (not negative) lead from the battery to the connection in the firewall and found a small amount of corrosion on the firewall connection. I cleaned both ends and reconnected and the flickering went away!!! I was shocked and surprised that such a small amount of oxidation could have that much of an impact. Nevertheless, the problem is fixed.

Thanks to everybody who provided input on this issue, it greatly helped.

PB2002.
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