instrument cluster lights

Hi all,

I'm usually pretty good at sussing up information from the internet. But I'm having trouble finding any information about instrument lights on an airhead. Mine are all out together, except sometimes my neutral light will work. I know there's an led panel out there and I have no problem going with that. But how do I determine that it's actually my flex board that's out? I'm not sure where to start on this one.

Thanks!

cue Kat

and her Katdash

I'm not up on where you are with this bike. Did the lights work at some point? If so, what was going on at the time that the lights stopped working?

I would think that if all the lights are out, it's not the instrument board perse but rather the signals to it. Have you checked the large plug that is attached to the back of the instrument cluster. Sometimes this can come loose or the pins have corrosion on them.

You may need to do some electrical work, measuring voltages into the cluster. Snowbum has a diagram for the /6 on this page:

http://bmwmotorcycletech.info/schematic1975,1976.htm

There are other versions of wiring diagrams located in a section in the bottom half of this page:

https://forums.bmwmoa.org/showthread.php?47142-Resources-and-Links

Your instrument lights are actuated and display indications based on input from "sensors", for the lack of a better word. The indicator for oil pressure comes an oil pressure switch. The neutral light is turned on by a different switch in the bottom of the transmission. Your high beam indicator is light is indicated by a circuit in the headlight relay. The charge light is legged off the voltage regulator, etc., etc,.

Each dash light has it's own input from the wiring harness. The common connection is the mini-pin connector on the back of the instrument pod, and/or the laminated circuit "board" inside the instrument pod. It is my understanding that the KatDash replaces that laminated circuit "board", I like to think of it as a circuit "film" since it is rubbery and flexible, and has copper ribbons for circuit conductors in the lamination. I think it is un-likely that all those input switches are failed. Therefore, I would be looking for corrosion at the pin connector on the back of the instrument pod, or the circuit board/ film inside the instrument pod.

While I have not installed a Katdash on one of my bikes, the testimonials tell me that it is a very good solution for the instrument lighting on /6 and later Airheads. My understanding is that Kat will eventually have KatDash inserts for any model from 1974 to 1995. Check out her web page to find out if she has a board for your particular bike.

Wow thanks for all the feedback! Ok to clear a few things up. The lights were all working during a 150 mile ride last week. They had gone out before in a similar fashion but came back on and I didn't think much of it. I agree with James, yes it's very unlikely that all the "inputs" have failed at once. So it sounds like the main pin is most likely my answer? I'm guessing I remove the screw and check the connections?

beano08 said:

So it sounds like the main pin is most likely my answer? I'm guessing I remove the screw and check the connections?

Click to expand...

That is what I would do as a first step.

Make sure the plug is in the back secure. I recently installed the Katdash on my 81 R100RT. The indicator lights are very bright in sunlight but I havent rode at night yet to see how the gauges look. Send her a message on your problem.

Use an OHM meter or a circuit tester and check each of the connections and paths on the flex plastic panel. I would bet it is a bad connection - maybe the ground as all lights were affected.

I think that it is possible to rewire yourself.

alright, well I'm stuck at square one. How do I remove the speedo and tach cables?! I turn them and they just spin!

There should be a very thin jamb nut...hold the nut and turn off the cable connector.

turn the metal barrel?

beano08 said:

turn the metal barrel?

Click to expand...

Yes. Usually found over tightened and you need a delicate touch with some channel lock pliers or some such. I've put a strip of leather on the really tight ones prior to applying the pliers to preserve the collar nut. Don't squeeze too hard. It comes off counter clockwise.