One for the electrical gurus out there

[rightrev]

One for the electrical gurus out there.

My car is a Porsche 1987 924S. Here is the problem.

When coming to a fast stop, or coming off the freeway to street traffic, I noticed that my oil light wound flicker. I then noticed that the “BREAK” light on the center column, but not the one in the dash gauge flickers in sink with the oil light.

Do these share a common lead somewhere than might be shorting out? Any other ideas?

Thanks in advance.

[nynor]

that is the way it is supposed to work. not a problem with the electrical. what is happening is that your oil pressure is dipping as you let off the throttle completely, which turns on the oil pressure light. the lights as you describe them are working properly, including the brake light in the center console.

[SoCal Driver]

Bad grounds between the engine and chassis and behind the gauges next to the drivers door.

[nynor]

i am telling you, this is exactly how my car behaves. i read up on it somewhere. but, socal driver is the man... trust him before me.

=)

as this is a 924S, it has the same guages, etc., as my '83.

[nynor]

er... wait! socal driver, does your '83 NOT do this?

[Eldorado]

my '83 does it..
not saying it's normal, but it does it...

only does it at idle (or moving in neutral or clutch in).... and the revs dip below 950.

[fast924S]

My 87 924S does the same thing, If I get low on oil or oil pressure the BRAKE light and The oil light will come on. I agree that this should happen and everything works normal. I think they do it to get your attention, because a porsche with out oil or oil pressure is not a happy one

[SoCal Driver]

Originally posted by nynor
er... wait! socal driver, does your '83 NOT do this?

It does NOT do as described. But then I keep the electricals all nice and conductive.

How?

Well the engine grounds were "freshened" when I replaced the engine about two years ago. The connections at the battery were "freshened" about the same time -- new battery. Also the starter connections were freshened when I had to replace the clutch slave about four months ago.

I suggest checking the charging voltage at the battery with all the bright lights on. May be a bad regulator in the alternator.

[Granite 944]

FWIW, none of my early cars are doing what you describe either. But like SoCal, all my grounds, and connections have been gone thru some time ago. Aux. ground wire added on the front of engines to the LF frame rail also. One car has the Iceshark full boat light kit on it, which included a new voltage reulator in altenator, which made a HUGE difference in that car. Flickering lights, doesn't sound like somethng normal to me, at least, not as described. The grounding "trees" behind, and above the fuse boxes, are hard to get to, and often overlooked, but on every car of mine anyway..........they looked really horrible as far as corrosion on the terminals when I cleaned up each one of them. Those trees are the main grounds for the fuse/relay boxes. Add it to your list of ground points to clean up.........maybe just not the first place to go until you've cleaned everything else up. Sid V is right ya know.

[SoCal Driver]

The under dash ground cluster does bear some resemblence to one of those cut and fried dipping onions you can get at TGI Friday's!

It's location above the fuse and relay block is a PITA.

[WolfeMacleod]

My '88 924S does not do this, and has zero electical gremlins.

[SoCal Driver]

So far....

[WolfeMacleod]

Originally posted by SoCal Driver
So far....

Shut up!

[nynor]

you better be knocking on wood.

[WolfeMacleod]

Originally posted by nynor
you better be knocking on wood.

I play guitar. I knock on wood every day

[nynor]

it is my understanding that if the oil pressure drops below two bar, the oil light comes on. mine comes on when the engine is hot, stop and go traffice, and i first drop the RPM's to idle, then it comes back up a bit and the light goes off.

[Granite 944]

Originally posted by nynor
it is my understanding that if the oil pressure drops below two bar, the oil light comes on. mine comes on when the engine is hot, stop and go traffice, and i first drop the RPM's to idle, then it comes back up a bit and the light goes off.

Then, it sounds to me, that you just might have a few issues you need to deal with also.

I'm not sure exactly at what pressure the light is suppose to come on, since I've never had the issue come up to deal with, and never researched it out. And yes, I do have the low oil pressure light, and it works. And....I have the "3pc" OPRV's in all my cars. I also think these 3 pc OPRV's get replaced to the 1pc more times than they really need to.


"The under dash ground cluster does bear some resemblence to one of those cut and fried dipping onions you can get at TGI Friday's!"

I must say, I never thought of it in that way.........now, I may have a hard time not laughing outloud, the next time I order this! ...........My wife will REALLY know I'm nuts then! LOL

[nynor]

i was concerned, til i read in the owner's manual that this is normal when the motor is at operating temp, during a hot day. the oil pressure only drops below two bar when the engine drops to idle, then comes right back above two bar. anything faster than idle, the pressure is above 3 bar.

[Granite 944]

Originally posted by nynor
i was concerned, til i read in the owner's manual that this is normal when the motor is at operating temp, during a hot day. the oil pressure only drops below two bar when the engine drops to idle, then comes right back above two bar. anything faster than idle, the pressure is above 3 bar.

Once in a great while, I could see the light "might" come on for a split second (never seen it yet myself), but, maybe you have the "shudder" condition more than me, or maybe its the type of oil you use, or maybe a dying voltage regulator, bad grounds/connections on block/frame/battery/oil pressure sender? I know its a lot hotter there in Utah........what weight oil are you using? Amsoil? Never tried it, I don't think its on Porsche's "recommended oil list" (TSB). I've been using Castrol GTX 20-50 wt. No issues so far, and I sure don't see "the light".

Even when I used a lighter weight oil (10-40 wt) for a while, I never noticed the light coming on like this. Pressure at idle was below 2 bar on hot days, and/or when car was good and hot. Thats why I'm staying with the 20-50wt, at least durring the summer. But then again, I live in the pacific northwest.......not the desert.

[nynor]

i do have a pretty good shudder when i drop off of the accelerator. it only does this when it is REALLY hot and any drop below 2 bar causes the oil light to come on. i am pretty happy with the amsoil, car runs nice and strong.