Strange HUD/Speedo Problem....might not be the usual

[po boy]

Background:93 SE Coupe w/Digital Dash & HUD, 5 speed

Couple months ago, my cruise control stopped working, then one day last week my LDC speedo stopped working (HUD too).Checked thru the FSM and there's no troubleshooting for the speedo/HUDDid some checking here. Had to re-register. Hadn't been here in a while, but I used to live here under another name in the early days. I've read the FAQ and this topic (zeropost?cmd=tshow&id=96108). Generally, I've searched this place up and down for all the speedo and HUD problems and have found some info, but I don't think any of it applies to me.

First, when I noticed the problem, I also found that when I would first turn the key to "ON", I would hear a high pitched whistle and the first digit on the speedo would faintly display "0". After a couple of seconds it would disappear. Everything else on the dash is working, including the lights that come on only when the headlights are on.

So, first off I switched out the complete meter units from my parts car, a 1991 240. This accomplished nothing, but I noticed that the replacement unit didn't emit the whistle or show any numbers, even faintly. And, the nighttime cluster lights didn't work with the spare unit installed. When I parked the 91 a few years ago, the dash worked fine.

Left the other cluster in for a day or two, and yesterday after driving about a half hour I pulled into a store for a Mt. Dew. Came back out and the speedo was working. After I killed the car at my destination and then started it to leave, no more dash, until I got a couple miles down the road and BAM, it came back on as I was driving. I started wiggling and shaking everything I could, but nothing made it cut off. Stopped by a friends house and when I left, nothing again.

So today I tried checking everything I found on here. I checked the diodes and they're fine. I switched the timer control between cars and it had no effect. I played around with switching clusters again and that's when I noticed that the original cluster was making the whistling noise and the cluster lights would work, whereas with the spare cluster there was no noise and the lights didn't work. So, I switched the actual LCD units between clusters.

This is the original cluster with the spare LCD unit in front:

When I put the spare LCD in my 93 cluster, it would not whine and night lights wouldn't work. I put the original LCD back in, and it's acting just like before....the soft hi-pitched whine along with the faint glowing of zero "0" on the rightmost number and the night lights are working.

Crap.....where do I go now? Any ideas on what's happening?

So far this makes three 240s with HUDs and two problems (had a 89 too that had gone on the fritz right before it was totaled.

Thanks guys.

[moegenki]

Most HUDs have that problem of just going out. I got a digital cluster from the junkyard one time and it was defective. The speedo would come on only after about 20-30 minutes of driving so I brought it to a speedo shop and they quoted me about $200 to fix the copper circuitry on the back.

[rexhunta]

If all else turns out to be too had, pick up an Apexi RSM or Pivot Speed Meter.. ebay usually has 2nd hand ones, or even new ones.. and they aren't that hard to fit in.

[po boy]

It's got to be the digital LCD unit. Everything else on my dash is working, including the nighttime lights. When I first cut the key on, the first zero faintly shines, then goes off. But, my odometer is still working too.

The spare dash I used must be really kaput.