Alan

The rear defroster relay is a double can 928 specific relay... However it sounds like its the switch or the trim around the switch **** - either one is significantly cheaper to fix...

Alan

SteveG

It should be added, don't disconnect batt on a running engine, hence the above procedure. I forget the reason, voltage spike? but it is one of the more important "don'ts" on this car.

SeanR

The engine will continue to run off the alternator and it can damage it.

SMTCapeCod

Seems this can happen with the HAZ switch as well.

Unless P/O swapped the switches between haz/defrost plugs.

95carrera

Old thread but interesting. Made me remember my problem on my 993. Due to screwy Bowden cable which runs between ignition and tiptronic shift lever you could not
turn car off. P mechanic said pull fuel pump relay if it ever happens. WD-40 fixed it.

Captain_Slow

I don't have that black 86.5 anymore..but this seems to be a common and scary problem. If it happens after you've pushed in the defrost button, try pulling it out. Good chance the engine will stop.

17prospective buyer

Yep same thing happened to me. Lol Sean have much experience with runaway diesels?

davek9

I've seen the Defrost switch do this too, however I would not stuff a rag into the Engine air intake, if you do, you will destroy the MAF screen(s) when the rag gets sucked in.

I would pull the fuel pump fuse and let her run out of gasoline.

Dave

Mrmerlin

FWIW simply placing your hand in front of the MAF will kill the engine, no rag is needed.
If a rag is used it could damage the MAF screen