jim912928

I have an 83 928s with 110k miles on it. Use it pretty much as my daily driver and it runs great. Even took two 500 mile trips in it this week. So, tonight I drive to the mall no problem. I come out and turn it on and the OXY light is on, the volt meter light is on and gauge reads 10, when I give it gas the "engine oil" light pops on and when I let off on the gas the "engine oil" light goes off. OXY light is on and the volt light/gauge still on and at 10. But none of the telltale signs of low voltage is happening (CD player is playing with no skips etc...). Even when I load on lights and blower fan for heat no movement/faulter on the volt meter which is registering 10.

Any thoughts?...This was like night and day.

Jim

p.s. I did check the oil immediately and it's fine so that idiot light warning is not accurate.

John Struthers

Similar post this week.
Disconnect battery wait a few seconds/minute.
reconnect.
MIGHT RE-SET ... might not.
Do a Load test multi-meter on battery.
Before start: what's your reading?
After start: Reading?
Lights on: Reading?
Lights, A/C or Heat ,fan on high. Reading?
A lot of folks say that their volt meter is hideously off the mark -can be adjusted -see archives-.
But, if you are used to 'seeing' a certain range on your particular volt meter while it may be inaccurate you can basically call it a baseline and if it changes -high or low - significantly from 'that' baseline something is indeed amiss.
!2 'real' volts may start your car but it is actually low. A 'real' reading of 15 volts is way to high.
The Guru's have said that ideal is somewhere around 12.8 - 13.5 volts.
So if you have an actual 12volt reading on a cold battery with engine off you are low, even this might be a false multi-meter reading because a battery can 'surface charge'.
If you haven't had a recent spat of wet weather, COLD weather, run trough some standing water,
I'd tricke charge the battery overnight and see what shows up on the multimeter, hopefully 12.8 or better.
If the battery runs down quickly after that I would either remove the alternator or take the car to a alternator/starter/battery shop. Good possibility that it's the regulator.
There are quite a few folks who will recommend that you take your reading off of the alternator terminals.
Thats all well and good of you can put your sHARk up on ramps or a lift and still start, add load.
Or, if you are double-jointed, have 5 foot long arms and telescoping eyeballs which makes the task a little easier.
I'm 235lbs, and a little arthritic so I test at the battery.
There are other culprits, corroded/loose grounds, loose connectors, broken wires ....
Stick with the easy ones first.
Battery: Test, charge. Maybe replace - only to find it was the alternator...bummer.
Alternator -specifically the regulator, thin second would be diodes.
BTW how old is your battery?
Good luck let us know what results are.

ViribusUnits

Sounds like eighter a weak battery, weak/bad alt. or a bad main grounding strap.

The numorous warning lights are symptomatic of low electrical voltage. Something about when the error checking system goesn't get enough voltage, it goes crazy.

The usual culprets are a weak alt., weak battery, or the main grounding strap. You can test the alt. and battery as described above. (btw, you only need 4 ft long arms, and there is no need for double joints to test off the alt.) However, to test the grounding strap you MUST remove it and use an ohm meter. Good looking grounding straps can go bad for no apparant reason. Also, check the grounding strap from the engine to the frame. They also can go bad at random times, and cause a similer problem to the above.

If none of the above are the problem, I'd check the ground under the dash. IIRC, all of the stuff in the pod is grounded there, and if the bolt got lose for some reason, the dash would act like it had low voltage, even if it didn't. Remove the bolt, and clean it up really good.

jim912928

Thanks all, I'll check this stuff today or tomorrow and let you know. The battery is about 1 year old and the alternator/regulator were rebuilt last spring.

SteveG

Viribus: I know (I) we have mentioned this before; I swear this is the last time I will ever mention it, once this nagging question is answered. You have pled dyslexia (my wife teaches reading so I am aware of its forms and my interest). And you claim your profs never penalize your spelling. If this social promotion is practiced beyond hs, they are doing you, a sufferer of dyslexia, a disservice and perhaps you should point that out to them. Though it has been suggested more than once gently, I have never seen evidence or acknowledgment that you know how to use spell check; if you physically cannot distinguish some letter patterns, spell check could help point them out. And since Rennlist has a button conveniently located below the icons, I'm wondering if there is something else going on that we are not aware of as to why you do not avail yourself of this feature?

GRGGOODSPEED

Disconnect the battery, for 30sec, start car (parked) for 10 min.,
Then turn off.

jim912928

Ok..this is what I did today:

1. Multimeter checks: battery/ car off is about 13v...car on with lights/heater/radio still at 13v
2. cleaned the ground back by the battery
3. cleaned the ground from engine to frame
4. check all the other "little' grounds (even under dash)..all was clean and tight

Still, when I start the car the OXY light comes on...volt dummy light is on...volt meter in car showing just above 10...engine oil light coming on and off.

blew the fuse in my multi-meter so can't do an ohm test on the ground straps..what should it be anyhow?

jim912928

Goodspeed..I'll try that next!

Garth S

Jim,
When you reload a fresh fuse in the multimeter, please retry a couple of voltage measurements: With the engine off, voltage at the battery should be 12.6v max - and within 12.4 +/- 0.1 at the hot terminal under the hood. That is for a new battery - a year old may be as low as 12.3v: values sustained of 13v suggest a 'surface charge' - and a battery going bad best confirmed by a load test of CCA (cold cranking amps). This is often a freebie at Auto Parts stores.
With the engine running, the nominal regulator control from the alt. is ~13.8v - measured at the same points.
Excuse the detail, but you should not see 13v as reported in either location with/without the engine running.

SteveG,
I will offer my opinion of 'Spell Check' - for as muck as I may attempt to massage the language into correctness, when I misspell of hit the wrong key - spellcheck in its blindness cannot recognize anything even slightly past a most close approximation of the correct word. The two planted errors above (muck = much, of = or) indicate misses on the most simple of words - my normal spelling errors absolutely confound this tool , leaving it of little use for my true 'fubars'..
One of the qualities I admire in posters is an inquiring mind compounded with the courage to develop a point - that is why I enjoy Viribus U's posts, and smile over spelling gaffs that I am quite capable of making.

mspiegle

i ran into an issue where my oil lights were going bonkers, and my voltage guages weren't accurate. Shortly after, my car wouldn't stop starting (yes, I take the key out of the ignition and the starter motor is still going).

It turned out to be a fried wiring harness up front. The shielding melted off because of the oil.

jim912928

Ok..latest tests:

1. car off, multimeter test shows between 12-13 (about half way)...eyes aren't that great so I was rounding to 13 before.

2. car on, multimeter test at battery still shows half way between 12-13

3. car on, heater and lights on...at battery still shows half way between 12-13

4. front of car using the pos connection for jumping it shows very close to 12..all the time no matter what load

5. I took the rear ground cable off and did a continuity test (I think..dial to ohms and a lead on each end?)....ohm scale went all the way to the other end of the spectrum from off. Not an electrical genius so I'm not sure if that is good or not

6. oh, did all this after battery was disconnected for about 30 minutes

Overall, car sounds good..runs good..but that OXS light and the charging light are still on with the gauge just showing above 10. Oil light is still blinking randomly on when I give it gas and immediately goes off when I let up. The warning blinker stuff goes on/off with that.

Garth S

Then, if we can trust the meter readings, the alternator is not charging. It appears that you have an analogue meter, but even a marginal one should pick up the differential of ~1.5volts between the battery and the alternator charging voltage.
How long has this been going on? FWIW, after an alternator died and left me stranded with a flat battery. I swapped in a marginally charged battery and drove the 25Km home - a battery can last quite a while: As the first battery was dying ( not being charged), I had a Xmas tree full of dash lights - like your car ....

jim912928

This just happened literally in a blink of the eye. Drove the car home and everything was fine. Drove to the store and everything was fine. Got in the car to leave the store and "merry christmas" the liights were blinking. Battery is about 1 year old and the alternator was rebuilt this past spring.

John Struthers

Say your alt wasn't a Paris-Rhone was it?
This is stricctly personal opinion:
The Paris-Rhone seems to work well for it's operating life but the rebuilds make great paper weights.
If you have the Bosche -and I believe there is one other model- see if you can swap the regulator -springs and brushes attached.
It's been awhile, but the unit is a 2 screw affair for attachment with two or three wires to connect. (I think)
Don't forget to disconnect battery when you work on the alt or starter lest you end up doing some unintended welding.

jim912928

alternator is a Paris-Rhone