Hi everyone,
About 4 years ago I designed and built a solid state relay board for my 914. I built a few extra ones and you can read all about that
HERE.


After building those I realized that not everybody wants solid state relays. So, I designed a version that uses the stock electromechanical relays. I started building a batch of 10 and I got distracted with another project. Recently, I had some more time and I completed those. This relay board uses the stock relays for power, heater and fuel pump. There are no provisions for the rear window heater. The relay socket used for the window heater is used to store an extra relay.
This board uses an ATC style fuse and has an LED that illuminates when the relay board is supplying power to the fuel pump. This is useful in diagnosing fuel pump issues. The LED illuminates for about 2 seconds when the key is turned on and remains illuminated when the engine is running.
I am selling this last batch for $325.00 each. This board does not come with any relays or the voltage regulator. I’ll cover the shipping and sorry, I can’t ship international. Message me if you want one. No need to reply to this post. I will edit this post and remove this section when they are all gone.

Okay, with that said, I will not be making any more of these. I will be making this design available to the 914 World Community. I have attached the 3D solid models (in STEP format) to the next post. Also, I attached a PowerPoint (PDF format) that outlines the construction process as well as the sources for all of the parts. There are 3D models for the solid state relay version as well as the stock electromechanical relay version.

This design and associated files is completely open source and can be used by anyone for any reason.

These boards are designed to be CNC machined from plastic. I used a CNC VMC. However, I think a CNC router would also work. I don’t think a 3D printer would work with the current design. However, I it could easily be modified to work.

3D Models.
I am not able to upload cad files to this site so I put them on my GrabCAD page.

https://grabcad.com/library/porsche-914-relay-board-1

Construction Details.

Would be happy to make a large run of these for those that want them and even add relays at a reduced cost.
Thinking keep the cost low znd just do mass production on the machined oarts, maybe do a kit?

interested

How about adding the rear defrost connection?

As admirable as this design and effort is, I see an issue on the wiring list.

The wire re: connection 1 is the circuit for the starter solenoid from the ignition switch. It needs to be a 10 ga wire not 14 gage.

Also, with the discrete wires as circuits why not just affix a gasketed, removable bottom plate instead of the potting compound?

Could be done, just need to machine it

I updated the wire list to the 10 ga wire for connection 1.

Wish this was available for the 914-6 relay panel as well.
I'd buy it.

Would be great to have a the solid state alternative to OEM board.

Mark, I'd be interested if you could get the volume up enough to get the price down. And offering as an assembly kit would be a good idea to reduce price.

GA

P.S., don't forget I still have your borrowed OE relay plate in my street car...

How hard would it be to make this up to use the standard square bosch relays? They are available in both electro-mechanical and solid state, so you would only need to make one.

Clay

Not too hard to change up, but why? The new relays are bullet proof and not that expensive for one you'll never have to replace.

Mike, for us guys in Canada I would appreciate it if you or another supplier would build us a copy that could be shipped to Canada.

While I no longer am using the stock relay board on my car I appreciate the time and effort you put into this Steve.

The documentation is 1st class and the willingness to openly share it all helps restore faith in mankind a bit.

Your relays are great. But if I don't have a spare on me, I am SOL. If we use the square Bosch relays, then any FLAPS has them in stock. Even a cheap horn relay could be used in a pinch.

Jeff I agree with the 10ga for connection #1 but I have a question on some of the other connections. Based on a current flow diagram I downloaded the majority of the original wire size, for regulatory board, was 0.5mm (18ga) and 1.0mm (16ga.). I'm I wrong to assume a 1.0mm wire converts to a 16ga vs 14ga on Steve's table?

0.5 mm^2 converts to 20 gage
1.0 mm^2 converts to 16 gage

Jeff now I'm confused. I checked a number of sites, like Rawell and 2-3 others and their conversion table shows that 1.0mm2 converts up to a 16ga wire which is actually 1.29 to 1.31mm2. The fact that i'm using GXL wire does that a different? Do you have a conversion chart that you could share? Any help would be appreciated.

This is the conversion table I downloaded from "engineeringtoolbox.com"Click to view attachment

Yes the idea is to make it as a bare bones kit in other words, do the part that not everyone can do and make it so that it's the least expensive option to get these.
-Mark