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Electronics cutting out.


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Hey everyone!

I've got a 2000 Boxster and have some terrible electrical gremlins.

When driving (happens much more often at night with headlights on too) my dash lights dim/flicker and my radio cuts out.

I have a brand new ignition switch put in, and my battery was just replaced yesterday as well (last one died after 1 year? Not sure if related or not)

Help?!

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Sounds like you still have the issues with a new battery. You may have issues with your cables. Visual inspection when good it's far from enough to verify the cables are healthy. You need to perform somevoltage drop tests on each cable to find out where you lose the voltage (flickering h adlights and dash indicate that).

Your symptoms seem very similar to Swaff's http://www.renntech.org/forums/topic/46275-power-surges-radio-turning-off-instrument-panel-flicker-light-flicker/

He had a bad battery negative cable, confirmed by voltage drop test between the ends of the cable when the flickering occured.

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I have a brand new ignition switch put in, and my battery was just replaced yesterday as well (last one died after 1 year? Not sure if related or not)

 

 

I installed a new ignition switch on my Boxster at the beginning of the month and had issues within a couple of weeks.  See this post: http://www.renntech.org/forums/topic/49343-light-switch-constant-illumination/

 

It turned out that the new ignition switch was defective.  I see that there are other possible causes, based on the other responses. But, as I learned, you cannot rule out premature failure of a new part.

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Sounds like you still have the issues with a new battery. You may have issues with your cables. Visual inspection when good it's far from enough to verify the cables are healthy. You need to perform somevoltage drop tests on each cable to find out where you lose the voltage (flickering h adlights and dash indicate that).

Your symptoms seem very similar to Swaff's http://www.renntech.org/forums/topic/46275-power-surges-radio-turning-off-instrument-panel-flicker-light-flicker/

He had a bad battery negative cable, confirmed by voltage drop test between the ends of the cable when the flickering occured.

How would I do this test? I read through his thread already, but I'm still unclear on it.

Also good point, with how cheap they are I'll get another ignition switch just for good measure and rule out the brand new one wasn't bad

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All you need is a digital multimeter. Just probe the two ends of the cable in question with your normal load ON (a/c, low beam, etc) and measure the voltage drop, which should be way less than 0.5v. For battery cables, touch one probe on the battery post that the cable is connected to and the other probe to the other end of the cable.

http://www.freeasestudyguides.com/voltage-drop-test.html

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New ignition switch didn't change anything.

Tested the ground cable - got absolutely no voltage drop.

Also tested voltage at the battery under load, 3-5krpm - getting 13.6-8ish on a brand new battery. Alternator maybe not putting enough out? Or is that okay?

What other things should I be checking?

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I would check the engine to chassis ground strap also (visual and voltage drop test). You may want to disconnect both battery cables from the battery and use those battery post cleaning tool (or wire brush) to clean the contact surfaces then spray them with Deoxit. 13.6v to 13.8v under load is not bad.

Also note the voltage drop test will be conclusive only if you do the tests when the flickering is actually occuring. Also put the multimeter into "mV" range.

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To test the ground strap (the cable on the passenger side of the engine that connects to the chassis), just put your probes on the brass ground bolt (connected to the chassis) on the airbox and any of the metal exhaust components (e.g., tailpipe or engine bracket, which are connected to the engine). This will test the ground strap itself plus all the contact surfaces between the cable and the chassis.

 

Yes the multimeter setting should be at 200mV. Also as mentioned before you should wait till the symptom shows up so you can catch the excessive voltage drop in the act.

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When the multimeter is set to 200mV, whatever it displays will be in mV. That means all your numbers above were 0.03mV, 1.8mV, and 1.4mV, which are excellent numbers! Anything below 500mV is acceptable. That means those old ground straps were good.

Basically there are 3 things in your case. The battery, the cables, and the alternator. The next logical step is to load test the alternator, which requires a load tester. A poor man's method is just turn on your low beam and a/c at idle (after engine fully warmed up) and check if you get 13.5v or above. When driving, you should also get 13.5v or above with low beam and a/c on.

Since there are a quite a few cables, you will need to check them one by one. Let me dig up an old write-up I have. When you light flickers, that means you are losing some voltage. The question is where.

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  • 2 weeks later...

Update: alternator shows 12.8 with my multimeter - took it to be bench tested, tests good 13.1 low, 13.9 avg, 14.2 high

So this means somewhere from the alternator up to the battery posts I'm losing power - correct?

At the cigarette adaptor i show 13.4-13.6

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"Alternator shows 12.8v" - where, how and under what condition was it measured? Whenever engine is on, voltage at the battery should be 13.5v to 14.5v, even wirh electrical accesories like a/c and low beam.

Don't trust the bench test too much as a lot of times the alternator acts up only when it's hot.

Did you get the tool I mentioned?

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12.8 when voltage is checked at the battery. This is when cold and warm and litronic low beams on.

When I have the voltage drops it doesn't seem to matter if the car is cold or been running for a while.

Also just ordered that tool today - should be here mid week next week.

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Are you sure when the battery measured 12.8v, the cig lighter socket meausured 13.6v? i.e., these readings were taken roughly around the same time and were repeatable? If that is true, I would suspect the positive cable that connects the battery to the power distributor under the dash.

Can you measure the voltage drop (set meter to 2V) between the battery positive post and the cig lighter socket positive? Should also clean the battery cable terminals.

Edited by Ahsai
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