Joe: The rear shock on these GL1800's is an "electric over hydraulic" unit. What that means is that whenever you adjust up or down an electric motor either pushes on or relaxes off the piston. This piston pushes on or relaxes oil pressure into the shock itself. When you increase the # the bike will rise up. When you lower the # the bike will lower. My first guess here is that you should look at the electrical side first. If you have a good (Honda preffered) service manual they have excellant wiring diagrams.
It is an 2006, out of warranty, and the fuse looks good. I tried the adjustments on the left hand panel per manual, in neutral.
It show the setting at 15, but will not go up or down. If I ride with a pillon, I like to set it higher, but now it won't change at all.
Thx, Joe (of JoeDee).
techdude might be onto something, but if there's an error in the control unit, it will tell you there's an error and won't go any further until you pull the POSITIVE battery terminal for at least 10 minutes.
If it's not telling you there's an error, then check the switch connections and also the relay bank. There are three relays involved. One is the main power, one is the up and one is a down. Uncover them and put your finger on them when you hit the switch. If you don't feel a click......
The rear shock is worked by a worm gear which puts pressure on a piston.
Disconnected the battery....took a break....came back and reattached hot wire to battery....nothing new!
So took off left fairing pocket, took off the adjuster panel below, wire harness to the panel was unplugged. Sprayed electrical cleaner in on the contacts, plugged in and now can adjust preload again....and an extra benefit of having emergency flashers also working again.
Thinking back now, I think the harness plug to the preload was inadvently left unplugged by the dealer when I had the bike in for it's 65K service.
Thanks again for your responses and giving me some direction to work in.