RPM drop when using electricity

[bcjm]

This problem is with my 88 Mercedes 300SEL but it applies to W113 also.  Each time I use something that requires high electricity the RPM drops for a second or two.  Most of the time it recovers but once in a while the car dies completely, especially at idle. Is there any possibility other than a bad alternator?  I am just very surprised that a bad alternator could cause this to happen.  If it is the alternator, should I try replacing the regulator first or should I go ahead get a new unit?


Thanks

[hands_aus]

Hi,

Could your batttery be your problem and not your alternator?

How old is your battery?

Bob (Brisbane,Australia)
early 250 SL, RHD

[bcjm]

Battery is the first thing I replaced.  Did not fix the problem.

[ja17]

Hello bc,
I would definately try the regulator first. The regulator and brush unit unscrew off the back of the alternator.



Joe Alexander
Blacklick, Ohio

[dwilli3038]

Hello BC,

Is it possible that there is no problem with the electrical system but rather something wrong with the "tune" of the car. When you use electricity, the alternator needs to take on some addtional load,  causeing the RPMs to just drop slightly , no different from turning on AC. This does not cause problems normaly, but if you have other problems it can magnify them.

Daryl
'64 230 SL
Serial # 508

[bcjm]

I took the regulator off the alternator yesterday.  The brush still have 25%-30% left. Can't really see anything wrong with the brush so I pressed the brush for a few times (a bit sticking) to make sure the spring is OK. The first thing I noticed after re-installing the regulator is that the noise in the stereo is gone.  It has been there for a while, does not matter it was in AM or FM.  The RPM stays complete stable when using any electrical device.   Hopefully it is not my imagination.