I had some questions about the engine oil light and ! light on my 1983 US 5 speed.

Some background: The past two days Ive been going through some start up procedures, as yesterday was the first engine start for the Ladybug project. Today Ive been letting her idle and warm up, checking fluids, monitoring for leaks, etc. I set the idle to 775rpm, I set the timing to 20' BTDC at 3,000rpm. While setting the timing, some gauge lights started to flash. Specifically the ! light and the Engine Oil Light. The lights come on when the rpms go above 1,800, then the light goes back off. I made a video below to help explain better.

For reference: I filled the engine cold with 8.5qts of oil to the high level mark on the dipstick. Once it was warmed up, the level on the dipstick was on the low mark, I added another .5qt to bring the warm oil level to midway between the high and low marks. From what the Manual says, it should only hold 8qts, A well respected gentleman informed me that Id need 9qts to fill it from complete empty. Could it be possible that the engine is still wanting some more oil (I estimate another .5qts to hit the high fill dipstick mark when warm)? And does the gauge light behavior reflect that, or maybe some other non related issue (electrical?). Would love to hear some opinions or ideas before moving forward. Thanks

Also as seen in the video, not sure whats going on with the voltmeter and the shift light staying on. Windshield fluid is empty for now so Im not worried about that one. all gauges were working previous to teardown from what i remember.

Movie time

 

Just to wrap this thread up for future users. I added .75qts of oil, to get the level to the top mark of the dipstick. Engine oil light stopped coming on during acceleration. Problem solved, so just in case anyone experiences similar symptoms. Also to note, it took 9.75qts of oil to fill properly from a dry engine.

 

The alternator charging the system disables the oil level light.

This way you don't get an inaccurate level warning when the motor is running and oil is not all in the pan. At least that is how mine works.

 

Noted. Thank you

 

thats a lot of oil..jeez

 

go higher in RPM, looks like an alternator issue. i had that with a 84, that wouldnt charge until the rpm went above 3k... do a test, put a volt meter on the system like you just tested and see if its charging. i bet it isnt. also, look at your voltage on the 928 meter, which looks to be at 10v.
oil pressure looks good. idle is way too low... thats how you make cams wear funny.
capacity of the oil is not including filter.. takes 9 quarts to fill a 928, only half dip stick. about 9.5 quarts fill a 928.

 

I suspect you might be right. Another suggested the same thing. Just haven't gotten to it yet. I'll try to make some time tomorrow and I'll report back. Thanks for the input.

 

when you do the test, rev the engine past 3000rpm or so and see if the lights that are blinking go out. i forget what my '84 problem was , but we never solved it.. it was just standard practice when i started the car up, that i had to rev past 2500rpm to start the charging circuit .. otherwise, it was running only on the battery.

 

I think that is a fairly common issue or behavior of Bosch electrical systems. There's a trigger wire that has to start the charging process and that wire wouldn't get enough voltage until the rpms were raised once to the 2,500-3,000 level. Both my Saab Turbo and my 914 exhibited this behavior.

 

I can confirm this. With a new engine wiring harness, green wire, and new alternator I had a voltage regulator fail. As soon as this happened, the engine oil light started to flash when I accelerated or cornered as did the center console big red central warning light, and my OXS lamp came on. The voltmeter lamp also stayed lit indicating that the exciter circuit was staying on.

This is not a technical explanation of the circuit details and my use of the terms off and on are to keep this explanation simple enough for me to explain it. That said:

Normally, the exciter circuit is turned off once the alternator starts to charge. However the circuit is not turned off if the alternator doesn't start to charge. In my case not at all in the above members case only after reving to 3000RPM.

The OXS lamp and low oil lamp are only on when the exciter circuit is on.
So when the alternator doesn't charge, the exciter circuit stays on and in turn, the OXS lamps stay on and the oil lamp / pan oil level pick up stay in circuit. The oil level pick up is only meant to detect the adequate level of oil at rest. Sloshing about the oil (whilst motoring) causes the oil and central warning to flash.

As soon as my regulator was replaced and charging system functioning properly, the oil level lamp and OXS lamps stayed off as soon as the engine starts, the alternator starts charging, and the volt meter lamp (exciter circuit) is off.

At all times my oil level on the dipstick was full.

Steve
83 928S Black / Pearl

 

thank you, all helpful information. Based on the responses I edited the thread title to include "alternator" since thats where this "oil light" thread is going.

On the collectives advise, I (familiarized myself with a multimeter and) took some electrical readings at the battery, jump post and alternator B+. Here's my notes



Important to note. I think its a Bosch alternator? The regulator says bosch but I don't see anything stamped on the alternator itself. number on the back reads 9555. Also, may be of importance, the empty male quick connect terminal near the D+ terminal. I noticed on another's photo of their alternator, there was a little black box and wire plugged into this male terminal. Not sure if Im missing a part?





I first went through some basic checks. Wire harness is new (so continuity shouldn't be a problem hopefully). If continuity check is still critical ill source an ohm meter and learn that procedure next. The terminal posts and nuts on the alternator have been cleaned, deoxited and properly tightened. The belt tension (new belt) has been checked and snugged. I noticed a slight bad-bearing-type noise at the alternator when the car was running. Also another note, the power cable to battery and battery ground cable are new and all grounds on the car have been recently cleaned and deoxited.

So how would one interpret the voltage readings in my notes?

Thanks for everyones help.
Josh

 

The alternator isn't charging. You should have 13-14 volts at the JP with the engine running at speeds above idle.

 

Thx Steve. I did another test this morning. I disconnected the blue wire from alternator D+ and connected a short jumper wire to the D+ post. With the car idling I touched the jumper wire to the B+. The first time I touched it, I thought I noticed a load increase (idle decrease), but the other 3-4 times I touched it, I didn't notice a change. I also simultaneously videoed the dash gauge. The gauge fluttered around 12-12.2v the entire time while idling, no noticeable change when I was touching the jumper wire vs. not touching.

What may be interesting is that with the blue wire disconnected from D+, the dash volt gauge reads 12-12.2v while idling. When the blue wire is reconnected to alt., the dash gauge is seemingly dead while the car is at idle.

Didn't do any rev testing, my helper (and better half) is still sleeping Am I on the right track?

 

Did some more testing and revised my first page of notes to add a column for Alt D+ readings. Also added another page of notes regarding readings at 14pin and the yellow light on the dash volt gauge. These to go along with tests performed earlier this morning outlined in my last post.

 

Also to note: no blown fuses at CE panel