[E34] Electrical gremlins after some time standing still

[whiskychaser]

With regard to the cluster, have you tried shining a torch at an angle on it? It is possible that the displays work but there is no backlighting.
The heater valves default to open so it sounds like the controls are not working. Same with the demister and AC.

I would start with the wiring diagrams

Was the dash removed for paint?

[Frank87]

Dash was not removed.

Heres the status:
- opened the instrument cluster. Replaced all bulbs just in case. No bad soldering. No bad components on the boards.

- experimented with a spare IHKA computer( the one with the 3 colored connectors). Same problem.

- removed the auc sensor and module just in case. Same problem.

- used a computer to read error codes. No errors other than a stratification potentiometer which has been in there for years. All sensors of the IHKA read good values except the interior temperature sensor which reads 60 celsius permanently.

- did whiskeys thing by shining at the lcd display. Odo and P D appear to display properly but with no lighting. The center bar shows an error "check control betriebsanleitung".
- removed the ccm module, checked it out and put it back in. Same error. Looking for a replacement ccm now.

Parts im getting soon are CCM.. spare manual A/C control panel and the parts required to fix the interior temp sensor.

Will let you guys know.

[Frank87]

Checked A/C parts near the dryer. Connectors were in bad shape and some wiring broke off upon touching it. Totally fishy.

Resoldered everything. Both pressure switch connectors are now rock solid. A/C compressor plug also resoldered and strengthened.

Still no A/C. I am sure the A/C hardware is now in good shape. I will continue once I have those modules in.