17prospective buyer

So, i started my S4 up for the first time in a while after letting a couple drops of oil sit in the cylinders overnight for lubrication when i start it. Well it ran fine, started up in 2 cranks. Well, it wouldn't shut off at the ignition switch. Kept running. Used rubber covered pliers to get the battery ground off, still running... Figured on unintentional chassis ground somewhere. Pulled the positive cable off, still running... figured unintentional ground on the alternator since after i disconnected both battery cables idle was loping and the battery voltage gauge read 14 where it usually only gets to 12. Clearly running off the alternator, so the safest thing to me was to pull out the fuel pump relay.

Currently printing off the engine compartment wiring diagram sheet, what should i start with?

Maleficio

Ignition switch.

yardpro

ditto

S4ordie

If you haven't named your car yet I recommend............... Christine.

SteveG

It is not a good idea to disconnect batt on a running car.

Randy V

So I take it you are no longer "17prospective buyer"?

Weren't thinking ahead when you chose that user name.

rbrtmchl

By any chance did you have your rear defroster turned on? I have read on this forum about the same problem of the car not shutting off, and the problem was related to the defroster. There can be some sort of back feed through a stuck defroster relay.

17prospective buyer

Can't really be on because my center console and all of the components/cabin controls that are housed in it i have disconnected so i can figure out the birds nest of wiring in there and trace current flow through those wiring diagrams. It can't be the voltage regulator since the gauge was vaguely reading what i estimated to be 14.5 which is normal charging output voltage for an alternator at idle.

Going to check the grounding for the alternator tomorrow. I think ignition switch is pretty likely though. I think i ruined my fuel pump relay in the panick to get it shut off. It was so tight in there i had to use pliers to take it out, and in the process ripped the cover off the relay. Luckily i was holding rubber insulated pliers so i could still just grab the whole thing and eventually get it out.

Lizard928

Next time, pull the fuse, #42.

Its the ignition switch. Replace it.

Mrmerlin

before you replace any parts,
I would inspect the rear window defroster switch on the pod ,
if it has been turned CW then the defroster is on so turn it CCW first.

Then start the car

If it has been turned to the CW position then there is a very good chance that the defroster relay has stuck on,
when this happens then turning off the key will not shut off the ignition.
The solution is to turn the key back to run,
then remove the fuel pump fuse.
It might be wise to open the defroster relay and clean the contacts.

Note you may also have damaged the voltage regulator or alternator by disconnecting the battery cables with the engine running,
after you start the engine take the multi meter and check to see what kind of voltage is being sent to the battery and the hot post,
test it at 1500 RPM it should be over 13.5 and under 14.2,
Lower than this then you have a damaged Diode,
higher than this you have a damaged regulator.

17prospective buyer

I'll do those tests you mentioned tomorrow Merlin, thanks. I really wasn't thinking when the car wouldn't turn off when i turned the key to full off position. I was just kinda freaked out and acted in haste. I guess the sudden current spike when i pulled off the positive on battery side could have cooked the diodes or capacitor in there like you said.

F**k sakes, it's always somethin' with 928's. Oh well, i have no deadlines for it to meet, and that is as we say, the fun part of owning a 928, the wrenching.

17prospective buyer

...Merry Christmas everyone! Merlin, if I tested the defroster relay when it's pulled out, it would be for continuity between the two switch contacts of the relay, which there should be if its stuck closed correct?

Mrmerlin

once the power is removed from the relay it may go open and will be hard to figure if its closed ,
best bet is to get another relay , used will work

BUT first take the cover off and clean the internal contacts then put it back in.

As long as the defroster isnt used it wont stick on,
and now if it does you know how to shut the car off,
once you pull the fuse,
then turn off the key and make sure the defroster is turned CCw to its off position,

then crank the engine this will shut off the relay if its stuck on.

NOTE the rear defroster relay has a timer in it, this is the part that either fails or sticks,
so you may have this issue again if the defroster is used