[E34] Electrical gremlins after some time standing still

[Frank87]

Hey guys.

I brought the E34 to Poland in march for full body restoration. I want Alkyd paint and for that I had to go to eastern europe where the interpretation of the law is very liberal.

Car body is 100% perfect. Total respray and restoration. I picked up the car and drove home. I have 2 issues now that were NOT there before:

- the instrument cluster has working fuel / temp / speed / rpm meters but the digital displays under it do NOT work. Also, the gong does NOT work if I purposely sabotage a light. So:
= I don't see the mileage / odometer
= I don't see any warning message neither do i hear the gong
= I don't see the A D automatic indicator
Not even the lighting of the bottom part works. Its just black as if the car is turned off

- the heater can only blow at maximum hot. Neither the A/C nor the regular "cold outside air" mode works. The heater valves were replaced in january with a brand new part.
- rear window defogger does not work. Press the button, the led will shine and then immediately turn off
- A/C doesn't work. Compressor can't be turned on
- AUC / recirculation doesn't work. Press the button, the led will shine and then immediately turn off


Anyone got any idea on the above issues where to get started? I plan to remove the heater valves and put 12v on the 3 prongs to test if i can hear them click or move. That takes care of the heater valve functioning.

I will also take the cluster apart to check for bad components on the circuitboard but something tells me the problem won't be there.

The A/C system has been full for the past 3 years. I have it checked each summer but they remove a 99% full charge every summer. I don't believe the A/C would be empty. I have replaced all A/C parts and rings a few years ago.

I have already checked all fuses and all relays. Also under the back seat.

[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.

[Frank87]

Had some modules to do some testing. CCM, LKM, GM5 and IHKA modules. 4 of each, no joke.

Swapped them all 1 by 1 and tested, nothing improved. My defroster, A/C, recirc and auc are still not working and the blower only gives hot air.

I have one more swap to make and that's the control panel itself. In addition I am going to check some ground points to make sure I don't have a grounding issue.

[632 Regal]

343 lookers so far at this thread. I have absolutely no idea what's going on but tune in daily to see what you find.

[Frank87]

I checked out some ground points and some areas where theres alot of cable. Nothing found. I have absolutely no clue now where to look.

Every module associated with the IHKA and general car stuff has been swapped. No change.

The problems:
- cold air doesnt work whether A/C button is on or off. IHKA blows hot only
- A/C doesnt work, there is no way to get the compressor going. System is leak free and full. All wiring resoldered where needed
- rear window defroster does not work at all
- check control on the instrument panel does not work. Bottom bar does not light up and if you shine with a light it says "Check Control, Betriebsanleitung"

I am going to take a break from this for a few weeks. It drives me nuts. I'll focus at some small mechanical things and drive the E39 daily.

[632 Regal]

Does the AC work if you jump it?

[Frank87]

Does the AC work if you jump it?

Fine idea!

I will jump it by jumping the relay. I think it will work as the system has pressure and keeps pressure. However, if the flaps in the interior do not work and if the interior does not close the heater valves, I wont be able to get legitimate cold air inside.

Ill let you know what happens.

[Frank87]

Before:
- 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.

Update to this thread:
- I have replaced the DME, no change
- I have replaced the Check Control Module, no change
- I have replaced the A/C control panel with an identical one, no change
- I have replaced the 3 buttons defrost/AC/AUC panel, no change

Problem still remain:
- cold air doesnt work whether A/C button is on or off. IHKA blows hot only
- A/C doesnt work, there is no way to get the compressor going. System is leak free and full. All wiring resoldered where needed
- rear window defroster does not work at all
- check control on the instrument panel does not work. Bottom bar does not light up and if you shine with a light it says "Check Control, Betriebsanleitung"

I have a total IHKA rebuilt. Going to swap it in a month or 2. Meanwhile I keep checking the electronics as I work on the car.