85 Carrera electrical issue

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85 Carrera electrical issue

Postby mljames65 on Sat May 16, 2020 8:31 pm

Fully charged battery discharging in about 5 days. Alternator shows 14.2 at idle, however, after a PCH run to Oceanside, would not start after a shutoff. Jump started and returned home at highway speeds with no issues. Was thinking possible flat spot at certain RPM not charging battery. Ultimately I think there’s an open circuit/short somewhere in the system. Usually have service done at Black Forest. Any suggestions on who may best be able to troubleshoot and cure this issue. Have also discovered the radio on without the key in if that helps. Pulling the face off the radio doesn’t seem to help.
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Re: 85 Carrera electrical issue

Postby kleggo on Thu Jun 11, 2020 9:23 am

mljames65 wrote:Fully charged battery discharging in about 5 days. Alternator shows 14.2 at idle, however, after a PCH run to Oceanside, would not start after a shutoff. Jump started and returned home at highway speeds with no issues. Was thinking possible flat spot at certain RPM not charging battery. Ultimately I think there’s an open circuit/short somewhere in the system. Usually have service done at Black Forest. Any suggestions on who may best be able to troubleshoot and cure this issue. Have also discovered the radio on without the key in if that helps. Pulling the face off the radio doesn’t seem to help.


How DIY handy are you?
Have an ammeter handy?
If so, connect meter and pull fuses until current draw goes to zero, that may be the circuit of interest.
But pulling fuses can disrupt some systems as they are powered down.
If what I'm laying down makes no sense to you, go to a real mechanic, not someone who plays one on the inet (me)

good luck.
Craig Fenstermaker

i'm here in Vista
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Re: 85 Carrera electrical issue

Postby mljames65 on Thu Jun 11, 2020 10:28 am

Thanks for the response.
I would call myself relatively DIY handy, however, Auto electric has always been a weaker spot. I do have a meter, just haven't found the time to give it a go just yet. Thanks again!
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Re: 85 Carrera electrical issue

Postby Steve Grosekemper on Thu Jun 11, 2020 2:05 pm

Michael,
You have multiple symptoms possibly caused by one problem.
Not starting after 5 days is one story, not starting after a drive is another.
But both with a radio that stays on sounds like an ignition switch issue.

If a charging system was intermittent the battery light would go on. (rare)
Check to see that the battery light is on with key on, engine off.

When it doesn't start check battery voltage; if above 12.4 then the battery is fine (12.2 is probably still enough to start)
If the voltage is good pull the 14 pin engine connector and bridge pin 2 and 13 (engine side of harness) and the car should crank.
(WITH THE CAR IN NEUTRAL!!!)

If it cranks you don't have enough voltage getting to the starter from the ignition switch.
Or there is an unusually high load at the starter.
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Re: 85 Carrera electrical issue

Postby mljames65 on Thu Jun 11, 2020 3:40 pm

Thanks Steve, appreciate the info.
I will check those items and get back to you. I’m coming due a major service in a couple thousand miles, I may just have you look at it then. :D
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Re: 85 Carrera electrical issue

Postby Steve Grosekemper on Thu Jun 11, 2020 4:06 pm

Sounds good and let me know.
But at least you will now have a better understanding of what is going on.
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