Electronic speedo

[Lock]

Using parts from an ebay broken e12 cluster, I put an e30 speedo into my cluster for a factory look, inspiration from here

https://www.bmw2002faq.com/forums/topic ... onversion/





The screws and odometer line up. Had to glue the needle back. Alignment of the unit was tricky, it's held in with back plates cut to size.

There's a resistor soldered on the board for calibration, I removed it and ran two wires to a variable resistor in the dash, went for a drive with GPS speedo and calibrated it. Then I measured that resistance, got an equivalent resistor and soldered it in place.

Works great - the trip meter doesn't work (maybe jammed due to the reset button not quite lining up) but it doesn't show completely anyway. It now reads the e28/e30/e34 hybrid diff speedo, and allows for e30 cruise control.

Also put in a 'check engine' and 'temp' light. I removed the brake and battery symbol by running a polishing dremel on it, took forever. The CEL connects to the Motronic CEL line, and the temp will connect to the e24 coolant level sensor. I couldn't find a good CEL sticker in the right size, but the below funny sticker pack turned out was the perfect size. They only come in yellow, no white, but near enough.

https://www.redbubble.com/i/sticker/Car ... 3487.EJUG5

If I did it again, I'd just remove the brake pad warning light and replace it, so much easier. But it did allow me to remove the center warning light unit so my dash mat sits flat now.

[PatinaBeforePolish]

Interesting. Did you do this just to add cruise, or...? I'm considering using mechanical to gps for more accurate speed readings.

[Lock]

A couple of reasons, my odometer was always broken, but the auto was dying when I bought the car so I soon swapped in an e34 5-speed which doesn't have a speedo output. So I've essentially never had a speedo - always used a phone with GPS speedo, those are frustrating because they can take a while to start working. I've had drives where it didn't work the entire time and I'm just guessing how fast I'm going, not a great reason to give to a cop.
But also I recently installed an e28 rear subframe (that's a whole other topic), which allowed me to use a diff with a speedo sensor. Having cruise control is an added bonus, and I found the e12 steering column even has the blank for cruise control because it's the same column as used in the 735i, so I bought a cruise stalk from an e23 and it looks factory.
I've looked into GPS speedos for motorbikes and if they work as advertised would be a great solution, a gps mechanical unit would be great for factory look especially if your odo is working already.

[PatinaBeforePolish]

Thanks and that's pretty neat you have cruise. I overlooked your swap so now it makes sense. Speedhut sells a converter that can use what they call a hot start wire which apparently saves the satellite positioning allowing for faster start up.

https://speedhut.com/accessories/sensor ... converter/

[528i-1981]

So with the factory Getrag 265/6 the speedo output will work in this arrangement?

Awesome project, Lock.

[Lock]

So with the factory Getrag 265/6 the speedo output will work in this arrangement?

Awesome project, Lock.

Thanks! I didn't get any pics of the cluster 'build', but when I take it out to fix some things like the trip meter I'll take some.

Re your question, was that for me or Patina? Looks like those GPS units can replace the Getrag speedo output entirely, so I could have used it before (even though my original odometer was broken too).

[PatinaBeforePolish]

Using the Speedhut converter eliminates the cable drive from the gearbox. The GPS unit feeds directly to the speedometer drive using the supplied cable.