Hi All,

As the title says, I have a '79 242DL, with what I hope is a one off, minor electrical issue. I welcome any input. To date this has only happened once but it was the last time that I drove the car.

The details:
-I was driving and everything was great.
-As the light faded I switched on my running lights. At first things stayed great.
-Within a few minutes I became aware of a relatively innocuous, intermittent "buzzing" sound in the vicinity of the cabin fuses in front of the driver's door below the light switch on the dash. Things were still pretty great as I assumed this was one of the many harmless sounds I've come to appreciate.
-Within a few more minutes the sound became grew slightly louder and became constant. I no longer though it was normal background Volvo noise and decided to have a look. I consider having a quick look in the fuse box one of the many relationship building aspects of life with an old car and was still optimistic that things would turn out great.
-I turned the car off and the noise stopped. All of the cabin fuses were intact and looked good.
-I turned the car back on and the sound started instantly at the same volume and level of intensity.
-I turned the running lights off and the sound stopped immediately. I looked at the key for the fuses and double checked the fuse (16A, I believe) labeled lights. It might have been labeled slightly differently. I'm not in the car now but I'm pretty sure that it was tied to headlights, interior lights, etc.
-I quickly flipped through wiring above the panel and didn't see anything that looked scorched or chaffed.

That's where things stand. When I turn the running lights or headlights on an electrical buzzing kicks in after a few minutes. Once it "heat's up" it is constant as long as the lights remain on. Nothing else seems to me amiss. I'm hoping for a happy ending.

All thoughts are welcome and thanks in advance.
Greg

 

You might want to use your $8 volt ohmmeter to check the charging rate. The voltage in the battery with the car off should be ~12.3x volts. With the engine running it should be ~13.6 volts. If not - do you still have 2 belts spinning the alternator? ( when ac dies to power the steering pump on some cars -, etc)

 

If its a buzzing sound it may be a relay. When your at home try to repeat the problem and then feel each relay. It might even be a relay that is not normally associated with the lights. Also a piece of hose held to the ear makes a good noise locator.

 

If it is an ongoing noise you should be able to follow the sound to the source.