Battery drain and possible blower malfunction
08-04-2004, 07:30 PM
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Battery drain and possible blower malfunction
I've got a problem with my '97 C4S that I bought in April. It's not my everyday car, but I drive it 1-2 times a week. After owning it 4 weeks it wouldn't start. Local Porsche mechanic (not dealer) said battery was no good, although it was only 8 months old. He said he tested alternator and it was fine. They put in new battery.
4 weeks later and it's dead again. Different local porsche mechanic (also with good reputation) said alternator output 12v, not 14+ like it should be, so he replaced alternator and charged battery.
1 week later (after leaving it 5 days while on vacation) and it's dead again. I disconnected negative lead from battery and tested with voltmeter. It's drawing 10.4 volts and about 105milliamps.
Mechanic and I both noticed that engine blower comes on and stays on for about 10 minutes even if the car is cold started, driven only a few feet and then shut off. It has been doing this since I got it. I can see how this might draw the battery down some, but would not explain the readings when the battery is disconnected and the blower is not running.
Any ideas before they try another expensive repair? Appreciate any help
4 weeks later and it's dead again. Different local porsche mechanic (also with good reputation) said alternator output 12v, not 14+ like it should be, so he replaced alternator and charged battery.
1 week later (after leaving it 5 days while on vacation) and it's dead again. I disconnected negative lead from battery and tested with voltmeter. It's drawing 10.4 volts and about 105milliamps.
Mechanic and I both noticed that engine blower comes on and stays on for about 10 minutes even if the car is cold started, driven only a few feet and then shut off. It has been doing this since I got it. I can see how this might draw the battery down some, but would not explain the readings when the battery is disconnected and the blower is not running.
Any ideas before they try another expensive repair? Appreciate any help
08-04-2004, 10:57 PM
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Steve,
The engine blower you're speaking of may be the secondary air injection pump, which runs with a cold engine. Though, it's not supposed to run with the engine off. Then again, it could be the rear heater blower, which would run if the cabin is calling for heat (temperature control **** set--say--over 21C, depending on ambient temperature). The rear heater blower also runs to cool the engine, but only when the engine is hot.
Anyway, as you suspect, 105 mA is way too high. Should be closer to 20 mA. You'll need to start pulling fuses until you find the draw. If you're measuring current with the trunk open, make sure you tape up the switch that activates the trunk light. It will cause a high reading otherwise, even with the interior light fuse pulled. Likewise, make sure the doors, rear lid are closed, interior light is off.
Hope his helps, and good luck!
The engine blower you're speaking of may be the secondary air injection pump, which runs with a cold engine. Though, it's not supposed to run with the engine off. Then again, it could be the rear heater blower, which would run if the cabin is calling for heat (temperature control **** set--say--over 21C, depending on ambient temperature). The rear heater blower also runs to cool the engine, but only when the engine is hot.
Anyway, as you suspect, 105 mA is way too high. Should be closer to 20 mA. You'll need to start pulling fuses until you find the draw. If you're measuring current with the trunk open, make sure you tape up the switch that activates the trunk light. It will cause a high reading otherwise, even with the interior light fuse pulled. Likewise, make sure the doors, rear lid are closed, interior light is off.
Hope his helps, and good luck!
Last edited by Randall G.; 08-04-2004 at 11:12 PM.
