Jump the hot lead to the compressor and watch it work. If not then you can trace it. If it works you can trace it. Not sure if I am missing a whole lot here just reading along.
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Often the AC compressor will only come on in run IF there is enough gas in the circuit. A good way to check is to get a refill can, tap and gauge pipe, seat the can on a scale, and attach it to the low side (blue) and see if there is any pressure. If you open the tap to introduce fresh refrigerant, be sure to note the mass the can loses, that way you know how much goes in. Sometimes as little as 30g will return the system to pressure enough to allow the low pressure switch to open and the compressor to engage. I have one that needs 50g every few years... I really need to replace the o-rings, oil and gas afresh, but I am not sure I'll ever get the time
I have a can of https://i5.walmartimages.com/asr/743...0&odnBg=ffffffI have not used and sitting on my desk. Debating weather to spend another $32 bux for little cans or get the mega jug for $130. I could have paid for the mega jug already. If it leaks out I have plenty of reserves ready plus maybe make some back filling other peoples stuff. I have all the gauges and stuff to legally do it.
I have fixed this problem.
I have:
- completely rebuilded an IHKA unit using 2 spares. Out of 3 big IHKA boxes I made 1 very neat, very clean and very good insulated (cut fresh insulation) one;
- fit and installed the above mentioned IHKA and checked all wirings, connectors and ground points;
- used a IHKA computer that was a guaranteed run on another E34 with similar IHKA;
- replaced a blown fuse. The fuse was not related to the IHKA (according to the schematics);
I now have:
- working rear window defogger
- working OBC
- NOT working mileage/automatic cluster (probably bulbs!)
- a working A/C;
- a working "hot" heater in 3 areas;
- a partially working cold heater (1 area cold only). The middle vent shafts blow cold, the window and foot ventilation keeps blowing warm/hot;
Anyone have any idea how window/foot area is separated? Could it be that one stepper motor that I put back is bad?
Either way, I got my A/C back and turning off window/foot area, car blows cold.
I assume (not sure) that the E32 IHKA is the same function, here are good pics and info what which stepper motor does http://bmwe32.masscom.net/johan/ihka/ihka.html
pdf Klimaautomatik German language http://www.e38.org/e32/klimaautomatik.pdf
My final problem, the A/C / cold outside air not blowing at feet and windshield was the passenger water valve not being actuated. I have remade/resoldered the wiring from the harness onto the water valves.
All works perfect now. I still do not know what the original problem was but since I have also removed wiring to the A/C compressor that should not have been there (completely non BMW wiring bypassing relays) and have used a 100% intact harness from a wrecker, I think whatever problem I had is now gone.
EVERY electric thing in the whole car now works exactly as it should. No error messages. No error code except for the aux. water pump which I have removed myself.
Great news.
Have the capacitors in the cluster been replaced? These will need to be done, if they haven't been. Not sure if the shut down the bulbs and doubt it, but if not, it will be a dry joint or a connector. Perhaps try looking- with the cluster apart and plugged in, for 8-12V on the light circuit, and the wiring/connectors leading to the information display PCB.