1977 300d charging issue

[nonextant]

Hi,

I have a 1977 300d and am experiencing the following symptoms:

battery holds a charge just fine over the weekend.
when driving, the radio started powering of when using the brakes..
now, when left idling the radio will power down.
when driving, everything has power, but I will occasionally hear a relay click from the driver side under the dash and my instrument lights will get brighter for a brief moment.

it started fine this morning and again after i got to work, but after driving around fort Carson for 15 min, when I went to start it turned over very slowly.

I believe the alternator is not putting out enough juice at idle or if the draw is too much, ie., headlights plus defroster and heater fan. But is putting out enough to recharge the battery during my freeway trip home.

I will check the wire from the alternator to the starter for corrosion tonight but am wondering if this is a common problem and see if anyone else has experienced it.

[Diesel911]

Charging problem seem to be resonably freequent.
You did not say if your Charging Light was going on or not.

Not sure where Ft Carson is but Harbor Freight Stores sell inexpensive Digital Volt Meters and that provides you with more information.

Next best is one of those Digital Volt Meters that plugs into the Cigar Lighter. However, I have found the one I bought seems to use about 1 volt to power itself. But, it is something you can watch while driving and can turn on you various accessories and see what happens.

From what I have read a lot of the nagging Charging issues seem to be caused by the condition of the wiring conectors and where they connect. The seems to be especailly so if you live where there is Snow or frequent Rain.

I found the below when I changed a Battery Cable:
http://www.peachparts.com/shopforum/diesel-discussion/328307-why-my-charging-voltage-increased-13-7-volts-14-4-volts.html


If you have the Digital Volt Meter you can do the below test:

AC voltage across battery to see if a Diode is bad:
VAC across battery should be under 100 mV; excess AC voltage on the DC line means one or more of the rectifier diodes in the bridge are leaking or shorted. Such a problem is relatively rare but unfortunately means replacing the entire alternator.

I did the above test and got what was a bad reading and checked another Vehicle and still got a bad reading. As it turned out that particular Meter had some issues because when I tested with another Meter the Alternator passed.
So if you test bad see if you can barrow another Meter from someone to verify it is bad.

[vwnate1]

This indicates the normal wearing out of the alternator brushes ,you change them by replacing the regulator as it's an assembly .

Off brand voltage regulators will never charge properly , only the BOSCH brands ones do the trick and they're only $2.00 more in price .

Many foolishly upgrade the wimpy originl 55 amp. alternator to the higher output ones from SABBS , newer Mercedes' and Volvos but , unless they have the correct BOSCH brand regulator (they never do) , you'll never ever see the correct 14.7 VDC the car and battery need to remain fully charged .

The best thing is : it's a 15 minute job to change it and all you neds do is jack up and safely block the right front of the car for easy access .

If you have no jack , drive up on a curbstone , this works for road side alternator replacements too .

[barry12345]

Sounds more like the glow plug relay is coming on and off perhaps. Or at leasty is a slight possibility. Since yours is under the dash above the drivers right foot it might be better to disable it for testing by opening up the fuse in the engine compartment. There are not many relays that you would hear an audiable click from on a 77 300d.

[kerry]

Originally Posted by barry12345

Sounds more like the glow plug relay is coming on and off perhaps. Or at leasty is a slight possibility. Since yours is under the dash above the drivers right foot it might be better to disable it for testing by opening up the fuse in the engine compartment. There are not many relays that you would hear an audiable click from on a 77 300d.

X2

[vstech]

X3

the alternator in the 77 123 should handle the window defroster, the blower, and headlights, with the wipers on. unless the glow plugs are energized. that 50 amp draw will totally kill the ability of the alt to keep the blower or anything else on.
(are you still on series "loop style" plugs?)
start the car, then check for voltage at the first glow plug. if you have volts, you need to change or upgrade the relay in your car.

[vstech]

another thing it could be is the blower motor itself may be failing. if the bearings in it are dry, the motor will draw excessive amps, and that combined with the headlights, radio, and defroster will overload the alt...
does the belt squeek?

[Diesel911]

I drove around in My Car with it charging 13.7 Volts for 5 years and the Manual has that that is above the minimum allowable Voltage and had no issues during that time with the Battering charging.
But, there is a difference between the Alternators ability to put put charging Voltage and Amperage.
I am not sure what inside of the Alternator could cause decreased ability to accept the load but the exterior wiring can cause that.

As suggested something could be malfunctioning or shotred causing the load to be too great for the Alternators Capacity.