Body and Interior Specific Aid

I've noticed some unusual noise in my Becker radio that I think is coming from the electrical system. It occurs when listening to an FM station as a sort of burping sound when at idle. An increased electrical load such as headlamps or a turn signal cause the sound to increase. Increasing the engine RPM causes the sound to stop. When listening to AM radio at idle, the sound is like a growl that rapidly turns into a screech as the engine is accelerated. Since this is a diesel engine, it can't be from an ignition circuit.

1983 300 td my heat only works when the heater wheel is on high. the solenoid in the heater line has been replaced. the engine is sufficiently warm billy

Does a 79 300SD have a pressure switch on the tailshaft of the transmission. I have an extra wire hanging from the kick down switch and was told there is supposed to be a pressure switch.

I browsed the forum topics, but couldn’t find a way to search them, so please forgive me if this question is redundant. I just flushed my A/C system with Hecat Flush, replaced all o-rings (assembled with Nylog), replaced the compressor (used new seals), receiver/drier, expansion valve and the short hose that goes between the condenser & receiver/drier. I added the appropriate amount of oil upon assembly, and took it to the shop to have it charged with R12. The shop said it held vacuum well and that the compressor was working properly. The pressures for the R12 are according to spec.