Error code not readable, ABS and motor lamp light, engine emergency run, heating is not possible

Moin, I’ve read many tips here and I hope the forum can help me. In short, the facts: Volvo V70 (I), 2.5l diesel (144hp), automatic, year 99. I have several problems that are probably connected somehow: On the one hand, when driving, the motor, ABS and brake lamp, tacho and DZM fail. Partially, the automatic arrow still flashes. This happens when the car is warm or it is warm outside. Leave a night and when it restarts, it’s all right. The assumption went to cold soldering points in the ABS control unit. Therefore control unit changed, nevertheless problem present. Readers (in free workshop AND at Volvo) connected, no one comes in to read or delete error code. In addition, my heating is without function. Control for the heating / air conditioning replaced, the same problem remains. I can turn on the fan with the slider, temperature control AND air flow flaps however I can not v If the car is driving, it feels like it is running in emergency run, i.e. the engine is driving, but does not have the full power (on the highway approx. 140max), switches late… All in all sea very annoying and unsatisfactory. Does anyone have an idea where I should look again / what should be tested? I can hardly drive with the car (no tacho, no heater, doesn’t pull so much..) Hope to find someone here who would have a hot tip!!! Bin aus Berlin, often also in the Hamburg/Lübeck area on the way THANK YOU IN THE PREPARATION!