Voltage Issue
 

I have 77 240d that I am getting small voltage drop or spikes (depending on which one it is). Here's a better explanation. I am seeing the lights; headlights, interior, and gauges showing small pulsations as I drive down the highway at night. Not severly like it looking like I am flashing my brights, just enough to notice. Is this the sign of a voltage regulator going? Or is this normal for diesels as this is my first? The alternator was replace within the last year and battery within the last 6 months.

I would check ALL grounding connections under the hood. Make sure the engine ground strap is intact. I believe you can see it from under the car. It installs where the enging bolts to the trans. It then hooks to the chassis. Check and ground the alternator if necessary. The only other thing is to replace the regulator with a BOSCH unit. The voltage regulators are a solid state type.

Belt.
 

Is the belt tight?

Jay.

I had the same problem with our 1978 diesel and replaced the voltage regulator which solved the problem. I am not a fan of throwing parts at a problem but with the help and advice of these forums I felt reasonably comfortable with replacing the regulator. Easy to do and inexpensive. It certainly doesn't hurt to use this opportunity to clean up the electrical connections either.

Jim W.

I second Motorhead's suggestion of checking grounding connections, and the connections on the alternator, too. Did you clean the connections and use dielectric grease when you replaced it? Dielectric grease is often overlooked when doing electrical work, but it really does help to make a good connection and makes plugs easier to pull apart. I use a Q-tip. Dip one end in rubbing alcohol to clean the connection, then use the other end to apply the grease.

Ditto.......dielectric grease
 

I was having the same problem a couple of weeks ago. Removed the alternator plug and applied some dielectric grease and no more flicker. That plug sits low and is susceptible to corrosion.

Unfortunately I inherted it with the alternator already replaced, so I don't know what was done when it was replaced. I will check all item that were noted and if all else fails, I will do the regulator. Thanks for the help guys.