Stuborn Electrical Problem '02 Boxster

[PB2002]

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.