mike cap

Everyone,

My 97 C2 had been in the paint shop for two weeks having the front and rear bumperettes removed and the bumper covers patched and painted.

The car was parked for about ten days and the paint shop owner told me that the car started hard (discharged battery). I stopped by and tried it and the battery was too weak to crank the engine over.

I thought this was odd, because the battery is a Diehard just installed 2 mos ago. I know that there is nore "parasitic" drain on the 993's than most cars and it is possible that when the paint shop moved the car around they may have left the ignition key in the accessory position. I already had the fuse pulled for the engine and hood deck lights. I was surprised the battery discharged so quickly.

Picked the car up last night and did a couple of quick electrical tests. I wanted to see if anyone else has numbers to compare to:

1) Parasitic current draw with ignition off, immobilizer system NOT set, key out and no interior, hood or engine deck lights on is about 100 milliamps.

2) Charging (bus) voltage at idle with no load on the system is about 13.8 vdc.

3) Charging (bus) voltage at idle, fully loaded with fan, lights, rear window defog, etc is about 12.8 vdc.

I fully charged the Diehard and then load tested and it is fine. When the car is in storage I use a battery milliamp "maintainer".

I did a search on this and could not find SPECIFIC numbers on 1,2,3.

Anyone have some numbers from their experience?

Thanks.

Mike Cap
1997 C2
Arena Red

Jeff 993TT

Seems a bit odd to me.. I've had my car parked for over 4 weeks before and did not have any problems starting it. It was up on jack stands and I was going in and out of the doors at the time, so at least the cabin lights were on periodically.

Jeff

Ray Calvo

The charging numbers seem low to me, as I remember. I have a voltmeter that plugs into the cigarette lighter; steady-state voltage when driving is 14.5 V. Then again, you're quoting idle nos. so they might be OK.

For info, I have a 993.

Ray Calvo

OK, temperature in the garage finally got up to something liveable, so I disconnected the battery maintainer and fried the sucker up. Here's what I noted about 2-3 minutes after the car started.

Charging (bus) voltage at idle with no load on the system is about 13.9-14 vdc.

Charging (bus) voltage at idle, fully loaded with fan, lights, rear window defog, etc is about 13.4 vdc. This is with NO AC but fan on full, headlights on hi beam.

I might have been in a bit of a fast idle; tach was a pretty solid 1000 RPM.

mike cap

Ray,
Thanks for checking this. That's pretty close to my numbers. I may hook a digital voltmeter to an adapter in the cig lighter and check the voltage going down the road.

Did you measure the battery draw (milliamps) at rest?

Mike Cap

Randall G.

Hi Mike,

100 mA is too high. Less than 25 mA is normal. Check out this thread:

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=3;t=005851" target="_blank">993 Current Draw</a>

You may find that you simply need to close a door/lid or tape back a light switch to get a normal reading.

Best of luck!