RichPugh

So... I need a good 12V source in the engine compartment, ideally on the drivers side, in or near the sealed relay/connection box. Short of running a power wire from the battery back into the engine bay, what are my options?

FYI, I've ditched the secondary air system and the cruise control so I thought to use something there. I am also ditching all of the OBD2 functions as the stock Bosch Motronic DME is being swapped out for a custom ECU.

The big 40A fuse in the drivers side relay/connections box for the secondary air pump was my original idea but it's not switched. It has power all the time. I did find switched power from my old cruise control harness but it's only providing 11.7-12.7V depending on RPM range. Strange considering the 40A fuse metered like 12.6-13.4V... ??

I need to power 3 PLX sensor modules. AFR, Boost/Vac and Fluid temp modules.

Inside the cabin is where the gauge module needs to be so I'll get power up there from somewhere.

Any recommendations? Thanks!

jstyer

Rear window defrost relay?

RichPugh

I just went out and pinned it out. Looks like the center position 15 IS a switched 12V. I think it could be a winner!

RichPugh

Found this... looks like the ticket. - https://rennlist.com/forums/993-foru...ter-relay.html

Position 15 for 12V switched, position 31 for Ground. Should be good!

AOW162435

Great avatar, Rich.



Andreas

AOW162435

Reviving this thread as I'm looking for a good switched 12v source in the driver's side engine compartment fuse panel.

I probed this relay socket and did not find center position 15 to be switched power. How can that be? My 993 is a 6/94 build date.




Andreas

windydog

Where you able to figure it out. I need one for my TPC piggy back.

AOW162435

windydog

Thanks Buddy!

So close. Just need to find a good place to attach the split second box. I hate to put it on the fuse box cover, YUCK!!!

pp000830

You could always use that 40 amp unswitched source you discuss above and throw a relay on it powered by some other ignition-on circuit. The install could be very neat and you could design it to use one of the standard relay types already present on a 993. Lots of options as to where to pick up the relay trigger voltage. If 25 amps will do it and you do not have heated seats you can pick up power under one of the seats at the seat plug and you are half way back to the engine compartment. If you really need serious amperage can the starter supply wire work before the starting relay also w/an ignition on relay trigger?