speedo intermittently stops

[digger]

The speedo intermittently stops working (all else on cluster works as it should).

The speedo doesn't jitter, bounce at all, it either works or it doesn't.

When it is working while driving and then dies the needle slowly falls to zero
When it is NOT working while driving and then comes good the needle slowly rises to show the speed

Does the lack of any sporadic or jittering needle behavior narrow down the focus?

[ehrawn]

I had the same problem. Researching the forum, it seemed like it could be a problem with the cluster: SI board, battery, loose solder connections, etc. I started with the pickup in the differential (62168355008) because it was easiest to tackle. It mostly fixed the problem. Next set will be a complete cluster rebuild from one of the recommended vendors to have all of the connection points resoldered.

[reelizmpro]

I had a speedo that did that once. I believe it was due to cracked solder joints. I would reflow the solder joints in the cluster, focusing on the main joints and joints that feed the speedo as well as the speedo itself. I would also inspect the SI board while there. Perhaps even replace it if you have a spare on hand. Make sure to use the right screws (short silver) to secure the center of the cluster surround to prevent damage to the SI board.

[Northern]

Both E30s I owned that were truly drivable had the wires snap at the diff connector. Some combo of strain and corrosion where the wire entered the moulded pin.
Speed signal would work 90% of the time, but drop to zero occasionally, for random amounts of time.
When it dropped out or came back, it would snap to the new position quickly, so maybe not the same as your issue but worth checking.

I ended up taking two pigtails from the same style connector off an e36 parts car and replacing the whole wire until I found clean copper under the back seat inside the cabin...

[digger]

i have a new pigtail to fix the diff plug because last time i was there the connector was crumbly and was my first thoughts as to the issue but ultimately i will address the cluster as i need to remove for another reason anyway