Solid State Relay Board Options

[Steve_R]

Well, it’s been about a year since I finished my 914 restoration, you can read all about it

HERE.

Everything works perfect except for the electrical problems I’ve been having with the relay board. I spent lots of hours trouble shooting electrical issues with the fuel pump. It turs out that my relay board had some bad connections for the fuel pump relay. After searching this site I discovered that the relay board is truly the weakest link in the 914. I tried to remove the epoxy bedding underneath the board and resolder the connections. This worked for a while but the fuel pump would sometimes stop and kill the engine. I finally figured out that the contacts for the fuel pump relay to the board were causing the problem. This seems like a never ending problem. I could buy another 40 year old used board and have the same problems.
So, to make a long story short, I decided to design a new relay board from scratch. I replaced the original electromechanical relays with industrial solid state relays. They have the same connection labels as the stock relays: 85 & 86 for the coil and 30 & 87 for the switch. The relays are available at most electrical parts dealers like Mouser or Digi-Key if one ever needs to be replace. They also use a lot less power than the original 914 relays. Also, since they are solid state and don’t have any moving parts they will last a lot longer and are more reliable. I also replaced the old ceramic fuse with a modern ATC style fuse and added an LED that illuminates when the fuel pump has power. This is great for trouble shooting fuel pump issues. It comes on for a few seconds after the key is turned on and stays on when the engine is running. Also, I removed the connections and plug for the rear window defroster. I used wires soldered to the connectors eliminating all of the riveted connections. All connections are soldered. To make the board I CNC machined the board out of high density polyethylene plastic.
I built a few extra boards to offset some of the development costs. They are quite labor extensive to build so I don’t plan to mass produce them. PM me if you want one. I would like to get $500.00 each. That includes the board with the solid stare relays. It does not include the voltage regulator. I used a solid state one from Pelican Parts. Both the stock and solid state voltage regulators will work.

[JeffBowlsby]

Drooling over this, I have some observations and questions:

* This board would not work for 914s with a rear window defroster
* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay?
* Would you consider making a kit with just the base and parts list/instructions available?

[Steve_R]

Drooling over this, I have some observations and questions:

* This board would not work for 914s with a rear window defroster
* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay?
* Would you consider making a kit with just the base and parts list/instructions available?

Hi Jeff,
* This board would not work for 914s with a rear window defroster .Yep, there was only enough room for 3 solid state relays. I read somewhere that only about 5% of 914 have a rear window defroster. Is this true?

* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
Good point. My car is a 1973 and I didn't notice that there is a difference. Are there any other differences between years for the relay boards?

* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay? . No reason. one of the relays I got had different fasteners.

* Would you consider making a kit with just the base and parts list/instructions available?
Maybe in the future. Right now I am working on another project.

[JeffBowlsby]

Drooling over this, I have some observations and questions:

* This board would not work for 914s with a rear window defroster
* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay?
* Would you consider making a kit with just the base and parts list/instructions available?

Hi Jeff,
* This board would not work for 914s with a rear window defroster .Yep, there was only enough room for 3 solid state relays. I read somewhere that only about 5% of 914 have a rear window defroster. Is this true?

* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
Good point. My car is a 1973 and I didn't notice that there is a difference. Are there any other differenced between years for the relay boards?

* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay? . No reason. one of the relays I got had different fasteners.

* Would you consider making a kit with just the base and parts list/instructions available?
Maybe in the future. Right now I am working on another project.

Your work is commendable Steve, I hope you can find a way to make these available to the masses. I understand that the 914 was one of the first if not the first vehicle to use a configured board like this and a modern replacement using current technology would be welcomed. If a kit was available, there are enough DIY types here that mounting the relays and wiring it up would be one way to minimize the investment. Maybe a group buy in quantity as well. Mark Whitesell may be interested in producing them with your assistance, especially if they can be molded or done in a production mode. "Mikey914"

The 914/4 boards were all the same, but the three harnesses that plug into them were different. The 1972-only ignition harness is the only one that uses pin 3 of the 12-pin, I don't recall if the chassis harnesses interface with the board differently, would need to research it. The /6 guys need their version just as much as the /4 guys do.

[Steve_R]

Drooling over this, I have some observations and questions:

* This board would not work for 914s with a rear window defroster
* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay?
* Would you consider making a kit with just the base and parts list/instructions available?

Hi Jeff,
* This board would not work for 914s with a rear window defroster .Yep, there was only enough room for 3 solid state relays. I read somewhere that only about 5% of 914 have a rear window defroster. Is this true?

* This board would not work for the 1972-only 914s that use pin 3 of the 12-pin connector for an oil temp sender circuit (to the dash gauge)
Good point. My car is a 1973 and I didn't notice that there is a difference. Are there any other differenced between years for the relay boards?

* Why the difference in the slotted/Phillips screws on the corners of each relay? Are those screws are ready power sources in the engine bay? . No reason. one of the relays I got had different fasteners.

* Would you consider making a kit with just the base and parts list/instructions available?
Maybe in the future. Right now I am working on another project.

Your work is commendable Steve, I hope you can find a way to make these available to the masses. I understand that the 914 was one of the first if not the first vehicle to use a configured board like this and a modern replacement using current technology would be welcomed. If a kit was available, there are enough DIY types here that mounting the relays and wiring it up would be one way to minimize the investment. Maybe a group buy in quantity as well. Mark Whitesell may be interested in producing them with your assistance, especially if they can be molded or done in a production mode. "Mikey914"

The 914/4 boards were all the same, but the three harnesses that plug into them were different. The 1972-only ignition harness is the only one that uses pin 3 of the 12-pin, I don't recall if the chassis harnesses interface with the board differently, would need to research it. The /6 guys need their version just as much as the /4 guys do.

Thanks Jeff.
I already spoke to mark about these. Unfortunately, when I designed this board I was not thinking about mass producing them. I have a good day job. I really just planned to make one and a couple extra to sell to help pay for some of the tools I needed. The board itself is machined from plastic using a CNC mill that uses 10 different tools (end mills and drills) and takes 3 hours to machine. My mill does not have an automatic tool changer so I need to be near the mill for the 3 hours. Also, the relays are industrial quality that are used in robots and medical equipment so they're not cheep.

However, I think it could be redesigned to be machined on a CNC router with one tool and use automotive solid state relays. Right now I just have too much on my plate.