Here's something I've been working on for a bit to help make sense of potential wiring nightmares under the dash.

If anyone sees any corrections that are needed, please let me know!

Hope this helps!

(Edit - Attachment was broken. Should be fixed!)

 

Nice! Thanks for the good effort. Unfortunately, it would take me hours to check your good work. But a good resource to use in conjunction with the factory wiring diagrams.

A photo of an actual panel might be helpful. It took me a while to recognize what the G and H terminals are. I know those letters are cast into the plastic of the panel but it didn't leap out to me until I had the panel totally removed and cleaned up.

Such as:

 

Harvey,
. It was actually your picture that got me started on this! (Found via Google Image search)

My primary questions revolve around the circuitry within the panel. (1) Power lines - I'm familiar with 30 (Btty), 15 (Ign on) - But what is X? It appears to be Ign Sw related. (Key in, but not necessarily on?)

Second question - There are what appear to be terminal points defined within the panel (per the schematic. ) I suspect they are relays, but where?

James

 

LOL. Glad to be inspirational!

"X" is a strange one. It feeds a variety of circuits and I can't see a common theme. It's possible that 15 reached some of amperage limit and Porsche just decided to add another circuit? Hopefully someone will chime in.

When you say "terminal points defined within the panel" I assume you are referring to the various relays that are shown within the grey boundary of the panel on the schematic. These are the relays that are integral to the panel, versus the ones that hang just off the edge of the panel and/or are mounted otherwise in the car. Hazard/turn signal flasher, horn, interval wiper.

 

The "X bus" is the ignition switched accessory power. Radio, wipers, HVAC fan, ect.

For some strange reason, the engineers decided that the 944 shouldn't have a 'accessory' position when turning the key, but have the accessory power come on when the key is inserted.

 

Harvey, the difference between 15 and X is X is unpowered while cranking. Most car's are wired this way. I guess they didn't want another 30-50 amp draw while cranking when it's 2 degrees outside.
I don't think it was the 944 engineers. The 944 engineers were probably given a Volkswagen ignition switch to work with. And who knows, it could have been Hilter telling Ferdinand Porsche "when the key is in, the radio shall play".

 

The photo and the schematic are perfect for my needs. I have been searching for that information for ages.
My 944 electrics have been progressively degraded by the PO's . Some of the rear plug pins, eg Headlamps,
have been overheated, necessitating extra relays to cope with the loads.
Thank you.

 

If you have extra relays running your headlights and fog lights consider yourself very lucky! Usually these are powered through their respective switches, which don’t handle the higher amperage’s well.