Captain_Slow

I'm sitting at work with the key in my hand and the 928 still idling. Mind shuffling through ideas for killing it. Then I ran through things I had done differently this morning. Only one thing -- I pushed in the defrost button for the rear window. So I pulled it out and the engine shut down. I tried it again after work to see if overnight condensation in the morning might have had some part in this. Apparently not, somehow pressing in the rear defrost button keeps the circuit closed even when the ignition is turned off and key removed. I'm guessing I have some wires with deteriorating insulation, causing a short. Mashing in the defrost switch is closing a gap between a couple of wires, pulling it out opens it....I guess. If pushing in the defroster button started the car I'd just leave the keys in my pocket. I'd tell passengers the 928 was the first car to offer push button start Any ideas on what is shorting behind the button are appreciated.
Jon

Landseer

Jon, search on this, others have seen it. Can't remember the fix, but it was an issue.

Where in VA are you. Looks flat. Tidewater?

Jadz928 (and I) just pulled the oldest 928 on earth out of that area.

Captain_Slow

Landseer,

Thanks! I didn't search because I never imagined anyone would have had this problem...just so weird.

I'm in Fairfax now. The photo is my previous 86.5 928, taken in Clarke County, VA. Miss the full cashmere leather. Surprised I'm not missing the sport seats at all. The standard seats are more comfy. My latest 86.5 is also black, not full leather. It's actually in better mechanical shape, and all the ventilation controls, switches, etc. work (most of the time). This one is not as pretty (could be), but is well sorted by PO for being a daily driver. Talked to the mechanic (Taylor Chapman) who's been servicing it most recently. He agreed, this car just needs to be cleaned up. He said it's a "very nice driver". Just what I wanted to hear.

Barry Chan

after you fix the problem, maybe just maybe you can somehow work it into a "928 push button start/stop" idea?

Farfelc2s

I had the same problem last month w my 997.
I took it to an indy, pulled a relay to shut motor. couldnt fix it,so he put it back.
Went to another indy right away, Finger flicked the relays. One of them had a cold solder when he opened it up. Fixed it, but bought a new relay anyway.
GL

Manfred

I think i remember it being the defrost relay

Captain_Slow

I NEVER would have guessed I'd have found this by doing a search... nor that JON in OZ would describe EXACTLY the problem JON in VA is having!

"I've heard this can happen if

The heated rear window switch is pushed in and does not pop back out again.
or
The heared rear window timer relay can stick in the on position.

Both causes give the same symptom - +12v is fed into the ignition circuits from the Power to the Heated rear window which is direct from the battery. This keeps the car running when you turn off the ignition.

Once the engine has been stopped disconnecting the battery normally resets the relay, but if the button is stuck in it needs to be pulled back out.
__________________
Jon in OZ

Rennlist Member
928OC Member

Black SE
Slate Grey '90 GT (hers)
Ex UK, Ex NZ (me and the 928s)

Captain_Slow

It would be nice if the defrost relay is a number 53. I have some spares. Will have to wait until the weekend.

pcar928fan

Often when the ignition switch goes out you get strange stuff like this too...

jon928se

Common occurence - you're on the right track with the defroster switch.

2 causes

Defroster switch can physically stick in the pushed in position - this can backfeed +12V into the ign circuit keeping the car running with keys out. - Pull switch back out.

Defroster timer relay can stick on causing same as above. Stop engine - stall it if a 5sp not sure if an Auto - then either disconnecting battery temporarily or restarting engine removes power from the relay unlatching it.

Captain_Slow

Too funny...JON, I found your earlier response on this issue. This may take a little bit of sorting out. Seems it could be the switch sticking (it stays depressed once pushed in), but it could also be the relay. If the switch is NOT supposed to stay IN when pushed, then the switch is likely the problem. I definitely have to pull the switch out to turn off the engine (after I've removed the key and it's still running).

Thank you very much. I can't get over how rapidly this problem has been solved (fixed soon) because of the people monitoring this forum.

Jon

jon928se

You must have found my earlier post while I was typing.

Switch is a "momentary contact" switch ie like a bell push on your front door. Shouldn't stick in. Normally gets snagged by a slightly distorted pod cover.

MGW-Fla

Yeah I had this same problem on my 1st '85. This was prior to it becoming known about the rear defrost switch & timer being the likely culprit(neither of which do I recall using). Everyone said to change the ignition switch, so I did, to no avail. It happened randomly & always only in the morning. The car was parked outside at night at the time, so the thought was condensation or temp change causing a circuit to stay open. My final solution was to start parking it in the garage & the problem went away! I thought perhaps my car was just of the feminine gender & was being fickle not wanting to be left outside at night! Seems like the '85-'86 models were the ones mostly having this problem.

RKD in OKC

Had a similar problem with the AMP relay.

SeanR

If you have this issue and need to get the car to stop running, pop the hood, pull the air filter out and shove a rag or your fist in to stop airflow. Car dies then you can unhook the battery ground strap.