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Starting to restore a 1989 928S4 row car. Pulling the interior at the moment. Can someone tell me what this switch is for and what the clear plastic box behind it is?
The clear box is your ignition protect circuit. Lose it. Order the replacement relay from Roger at 928srus. You don't want that to activate, dump fuel in your hot cats (think woosh) and possibly snap your driveshaft from uneven firing pulses. No idea on the switch though.
I have seen this switch before in one of my parts cars. In my case, it was wired as an ignition kill switch. Literally wired right into the back of the ignition switch
Edit. I should add that mine was identical with same wires and same location.
Thank you everyone for your replies. Appears to be an ignition cutoff, spliced into a small harness just in front of the clear box. Yellow wires are marked A1 and A2. Will install the battery tonight and see if the switch kills ignition. The kick panel cover is missing and the factory like switch mount made me think it was something else. Switch button is damaged and I thought it possibly shuts off local power when you remove panel.
The clear box is your ignition protect circuit. Lose it. Order the replacement relay from Roger at 928srus. You don't want that to activate, dump fuel in your hot cats (think woosh) and possibly snap your driveshaft from uneven firing pulses. No idea on the switch though.
Jeff - The IPS is designed to avoid raw fuel getting to the cats. If does start getting raw fuel (causing a lower manifold temp) it will activate - that is its sole purpose. Removing it will ALLOW that to happen. Yes if it does activate you will lose power on one whole bank - but the engine will still run - very poorly and possibly not at idle - but you are not really supposed to drive it like this at least not very far (just to safety). I can tell you - it is entirely obvious that you just lost half the engine if it happens when driving. If the IMS still works don't take it out - they are generally very reliable, if it ever activates you probably do actually have spark-miss (plug/wires/dist/coil/final stage) issues that need to be fixed to avoid a cat fire.
^^ It cuts power to the fuel injectors, not the ignition system. Chances are if it activated you had an ignition amp go bad. They're the most common source of losing half of your cylinders.
Of course it deactivates the injectors - to avoid raw fuel getting to the cats you have to do that. The cause is usually no spark for any of the reasons I mentioned including the final stage (what you call ignition amp). Taking out the IMS increases your risk of a cat fire - that's why they put this system in. It is generally very reliable.
It appears I had this backwards. I took mine out after a failure. That was 9 years ago. Didn't want to snap the old driveshaft as others told me would be prone to happening. It's in a thread on RL somewhere when I talked about it.
10-05-2021, 10:32 PM
What is this?
