Loud buzzing from trunk/antenna

[London]

Would appreciate some help diagnosing this sound. I've searched the forums and Bentley but can't sort it out.

1986 325es moved the car from sunny climate to the PNW. Car got a lot of water in it over winter, I've dried/cleaned it out, charged the dead battery, and as soon as I connect the negative terminal a high electric buzzing/whine starts up and sounds loudest over near the antenna and whatever wiring is behind it.
Car still starts and drives fine. Speed doesn't affect buzz, it just continues whether running or not. Only other thing acting up is that when I try to use central locking from the trunk both front doors do the lock/unlock thing like one of them was open.

Halp. I don't want to hear this sound anymore!

[Das Delfin]

sounds like your trunk actuator is stuck.. unplug it and see what happens.

[turbo55]

Or maybe the external fuel pump? It's right in front of the rear wheel on the driver's side.

[jeffnhiscars]

Noise at the external fuel pump is usually a sign that the internal,pump has failed so the external is sucking instead of pushing which causes cavitation in the line.

The antenna itself should time out but if the board is bad, say from moisture, and you have a stripped mast, it's possible for it to just keep grinding (plastic on plastic).

I'm not aware of the lock mechanism ever just making noise.

[Seawolf]

Do you get this sound with both key off or key on (acc / run) ?

If it's key off that would be weird since there isn't anything permanently powered in that area that I'm aware of with a stock wiring configuration.

If it's key on then buzzable stuff in that area is antenna, amp or left rear speaker. Easy enough to disconnect and eliminate.

[London]

I'll mess with the actuator next. Also, Air wont blow. Did these systems share a common connection somewhere? All fuses look fine. PNW winter did a number on the old girl :(

Does external fuel pump run with key off?? I assumed it only operated when the key was on. This noise begins as soon as the battery is hooked up even if the key is in my hand hah.

[Das Delfin]

I'll mess with the actuator next. Also, Air wont blow. Did these systems share a common connection somewhere? All fuses look fine. PNW winter did a number on the old girl :(

Does external fuel pump run with key off?? I assumed it only operated when the key was on. This noise begins as soon as the battery is hooked up even if the key is in my hand hah.

the ext pump is not supposed to run with the engine off but you could have a wiring issue causing it to run. Your best bet is to get a multimeter and systematically these circuits for abnormalities

ie check that the ext fuel pump isn't getting voltage without the motor running (also unplug the fuel pump relay to double check), then unplug the antenna and see if the noise persists. Unplug the lock actuator and see if the noise continues.

Your air problem could be fuse 20 needing replacement.. do you mean air as in A/C? Or air in general? Does your heater work on all 4 settings or just one? Does your fuse 20 look melted?

All this should take 20 mins with a meter.. not hard at all

[London]

Never figured out what the problem was... I went to investigate and it didn't happen... Buzzing hasn't happened since soooo fingers crossed for now? I'm still trying to figure out why my fuse 20 keeps blowing but we'll see what happens