924Board.org

[ltgland]

My car is having SEVERE electrical problems!
The idling seems too low and the following happened today, which confirms my fears:

when leaving the shopping centre in the rain, my windows were misting. I had the front wipers on 1, the rear demister on, and the fan on 3. The engine died completely, and only after I killed the fan, would it restart. The rear wiper also failed to work (it worked fine on the way in shopping).

The bit that scared me was:
when driving home, I had to rev high to stop the engine from die-ing, The car spun out severely on a corner (I was going 15-20mph at the most), The nose spun and I was 90 degrees to the road. A correction steer put me at 45 degrees the other way, then I regained control. This scared the crap out of me, and the taxi on my six stayed well back for the rest of the journey (funny that). I suspect electrical load problems, which points to grounding (I guess). Where do I start?

[Smoothie]

How old are your battery and alternator? If the car was already running, the alternator should have been putting out enough to keep
everything going. Is it possible that the rain was causing the alternator belt to slip? Maybe need to tighten that. I cured all my low current problems last year by putting in a 140 amp alternator. Before that I was going through batteries too fast and lights would dim as I turned on more electrical devices. I replaced the Bosch with a Delco CS-144 140A alternator. If you want to stay with the Bosch and a loose belt isn't the problem - might only need a new voltage regulator (if the battery is also good).

[Smoothie]

Me again - A few years ago while driving at night, my headlights started going dim, very dim. I realized that my alternator had given or was giving up and I was running on what was left on the charge in my battery. I was only about a mile from home so I shut off everything electrical including the lights, turned around and just made it back home. The engine started running rough before I got back so the lack of current was starting to affect the ignition and fuel delivery. The fix for this was a new voltage regulator.

[ltgland]

the cars just come back from a service, the altbelt was ok. I like the idea of putting in a bigger one. I suspected pokey groundings, but where to begin.
The scary bit was having to rev hard. I took a corner, and then teh car spun out. Damn, I S**t myself. Lucky for our hero he maintained control of his vehicle. Maybe I should race against Vaughn

[Joes924]

Ive never spun out.When I had a dead alt the motor would never stop worken the wipers got real slow though.Once off it wouldnt do anything.

[Geddy T]

What would losing traction have to do with electrical problems? Or did you just spin out because you were revving it so high to keep the car running? I had this same problem recently. I installed a new alternator and didn't torque down the ground strap tight enough. A mile down the road I tried to roll up my windows and the crept up a little and then stopped. Then a turn signal didn't work. Then I crapped myself. The battery was almost dead as it was and I was getting no charge from the alternator. So I pulled over at a shop that was close by. The alternators are rubber mounted so that grounding strap is important. Many mechanics don't understand this. In fact, the mechanic that I pulled over at told me that the grounding strap didn't do anything at all and then quickly retracted that statement when his prybar that he was using to tighten the belt caused a shower of sparks (when it grounded the alternator to the intake manifold). Also, make sure that the alternator isn't jerking around like crazy. I really don't like the rubber mounts and plan on fabbing a solid metal one to tighten it down. Your bearings in there can go bad really fast if it's shaking.

[kevrl]

Just to confirm what Geddy mentioned. A few weeks ago, I neglected to put the earth strap back on to the back of the alternator. If the car has just had a service, possibly a non porsche familiar mechanic has removed it, or alternatively moved the alternator to the extreme of its travel causing the ground strap to snap.

On my car it caused dim lights and a slowly falling battery voltage as shown by the voltmeter in the car. When running this should be at between 12-14volts, without the ground strap it will read about 10 volts.

For low idle, check the idle valve connector and timing. Both these can cause low idle at various stages of engine running. (obviously as well as mixture and idle bypass)

Kevin

[ltgland]

"What would losing traction have to do with electrical problems? Or did you just spin out because you were revving it so high to keep the car running"

option 2.
But the car went back today, the redid the timing, which upped the idling from 500-600 to 900-1000, which makes HUGE difference. I blew yet another fuel fuse though, and they said the fuel wires were getting very hot. Something is pulling a lot of current, more than likely the fuel pump. Since its very noisy, the reckon thats the most likely cause, which makes sense. I will be checking out the Technical section for fuel pump replacements when I have the money.

The altinator grounding is interesting, thats something I need to look at. I also noticed that when I played with the altinator air hose, I got better voltage out (from 12ish, to about 13 ish) . Its not clamped on, so I pushed it on real hard. Not too sure as to why cooling the altinator has anything to do with anything, but it seemed to have a positive affect.

[Smoothie]

Electrical resistance is lower at lower temps. You've probably heard of supercomputers and superconductors and how they require very low temperatures to maintain a superconductive state? I used to work with an IBM mainframe computer that had a liquid cooling system built into it. Coolant was pumped all through the circuitry and it wasn't even a "supercomputer". Well, just as low temps allow current to flow more freely, high temps hinder it. So be nice to your 924na alternators and keep them cool. (924T's have them mounted top center and away from the exhaust so there's not as much of a cooling problem with them.)