Is this normal? 1983 300D odd startup dim lights

[psaboic]

As the title says......

I have an 83 300D with roughly 240K on it. First winter driving it. Anyway this may be a stupid question but here goes.

On the first start of the day, or anytime after sitting for over 6 hours, the headlights and instrument lights are dim and the fan motor seems to be running at half speed after the car is running. This continues for at least five minutes after starting (if left to idle), or for about a minute to two minutes after driving. Then suddenly, it is if someone threw a switch.....full power to everything, and all is fine until next overnight start. I checked all connections to the battery and alternator, and the alternator belt is snug an not slipping.

Any clues? I do not have a volt meter installed in the car so unless I get out a DVM I'm not too sure what voltage I'm putting out. Oh yes, the charge light works normal at start up and never comes on during the low power issue to indicate trouble.

Thanks for any help.

Glenn

[pawoSD]

That means your car likely has the Bosch afterglow glow plug relay on it. When the car is started the glow plugs remain energized (drawing over 50-60amps) and dragging down the voltage of the electrical system for a few mins (its actually about 3 mins) then it clicks off and everything returns to "normal". The original alternator on these cars is not strong enough to counteract that load, especially if other things are on too. Completely normal. Solution is to install a higher output alternator. I have an 80A unit on my car and above idle it can handle most of the need so there is minimal voltage drop. A 90 or 100+ A unit would easily handle it all.

[tyl604]

PawoSD - what would be the purpose of the afterglow glow plug relay that continues to draw current after the car is running?

I have the afterglow relay with the stock alternator. It reduces the voltage for the first couple of minutes, but it certainly doesn't slow down the engine idle.

[psaboic]

Thanks for the quick reply. Glad I do not have anything to worry about. I will make plans to get a bigger alternator soon though

[vstech]

Thayer are you reading this post?

[compress ignite]

Tyl604,

The "After Glow" (Continued Energization) of the Glow Plugs assures proper
"Warm Up" cycle of the Cylinder/Piston Temperatures AND more importantly
proper Fuel Burn with a COLD engine.
MB installed the system as a Emissions preventer on a Cold Start.
BUT, The Bonus is a smooth quiet idle without smoke when COLD.

You can retro fit an AfterGlow enabled Relay and Glow Plugs,if your MB
doesn't have them already.

[pawoSD]

The cars did not come with this relay stock, it is sold as the replacement/upgrade unit. It makes a big difference in cold starts and idle quality when cold.