Electronic Speedo

[E Sully]

When I installed the '86 3.2 engine and tranny in my '73.5, I also had to convert to an electronic speedometer. Of course, the one I purchased did not work, despite the sellers claim. I sent it to DNA speedo in Florida, and they said that it would be about $200 to custom build a new board, since the processor was shot and they could not get a new one. The best I could get out of the seller were 2 other non working speedos.
I set out on a search and read all the threads about speedometer repair. I sourced out 4 new 2115 boards made in Taiwan, went to Radio Shack and purchased the higher voltage capacitors and started in on them. I have no real circuit board soldering experience, but with a 15 watt soldering iron I set to work.
I am happy to say that I now have 2 working speedo's. They slightly over-read the speed, but from what I've read this is normal. Next step will be to try and calibrate them for speed. I found another link about changing out one of the resistors for this. Of course, the odometer gears need changing also, but I must wait for my order from pelican for that.

[Andy911sc]

I am currently looking into some speedo issues myself. I have a speedometer that is reading slow. I have a new speed sending unit in place which picks up all the magnets and have torn the differential apart to verify all magnets are there. I recently had my speedo out for gear repairs and have dropped a little more than I wanted in the repair. The also fixed some internal electrical problems and a cracked internal housing.

My speedo is still reading slow (when going 37mph, it reads 30).

My question is, can resistors that are failing cause this since you mentioned changing them to recalibrate speed. I know resistors can either fail open or fail by increasing resistance. I suspect that an increase in resistance would slow the frequency from the speed sending unit causing a slower speed.

Any help would be greatly appreciated.

I am taking my speedo back today to have them fix a 1xx,xxx millage roll over they goofed and relook at the speedo for correct speed read-out.