1984 300D alternator Battery puzzler

[marybeth]

1984 300D (sons car). Low volatge (11.8 at idle 12.7 reved). Battery tested good. Voltage regulator looked "poor" so had replaced and Bosh Alternator tested (Tested good).
Ohmed out all connectors/cables from Alternator to "black box " on Fender to Battery. Even Dremeled shiny all the battery clamps.

Still same issue-11.8 at idle and 12.7 max with motor reved.

I am stumped....any ideas?

[Brian Carlton]

Originally Posted by marybeth

so had replaced and Bosh Alternator tested (Tested good).

They didn't replace the voltage regulator and claimed the alternator is "good".

[Diesel911]

Originally Posted by marybeth

1984 300D (sons car). Low volatge (11.8 at idle 12.7 reved). Battery tested good. Voltage regulator looked "poor" so had replaced and Bosh Alternator tested (Tested good).
Ohmed out all connectors/cables from Alternator to "black box " on Fender to Battery. Even Dremeled shiny all the battery clamps.

Still same issue-11.8 at idle and 12.7 max with motor reved.

I am stumped....any ideas?

After the Voltage Regulator was changed was the Alternator tested on or off of the Car?
If the Alternator tested good off of the Car on the Alternator Test Stand there is a good chance the no charge issue is being caused by something else on the Car.

This question is for anyone who has the answer.
It seems like 90% of the time when someone is having a Charging System issue they never tell us if the Alternator Charging Light is lit or not; why not???

[Junkman]

I installed 3 Bosch regulators over time before finally getting a good one. Unregulated, the alt would charge high (I forget how high but I had it bench tested.)

[Brian Carlton]

Originally Posted by Diesel911

This question is for anyone who has the answer.
It seems like 90% of the time when someone is having a Charging System issue they never tell us if the Alternator Charging Light is lit or not; why not???

I know where you're going with this but it has been established that these vehicles don't need that light to charge.

In fact, right at the moment, the light on the SD is non-functional and it makes that circuit via another source. It takes about 1100 rpm to do it, however. It's an interesting circuit with a small resistor within it.

[Diesel911]

Originally Posted by Brian Carlton

I know where you're going with this but it has been established that these vehicles don't need that light to charge.

In fact, right at the moment, the light on the SD is non-functional and it makes that circuit via another source. It takes about 1100 rpm to do it, however. It's an interesting circuit with a small resistor within it.

I don't know what to say on it charging without the light in the Circuit.
I have read that sometimes when it is not charging the Light does not go on; but that is different.

It is another bit if information that could help find out what is wrong.

As an example if He had said the Charging Light was on all of the time while the Engine was running.

[Diesel911]

Originally Posted by Junkman

I installed 3 Bosch regulators over time before finally getting a good one. Unregulated, the alt would charge high (I forget how high but I had it bench tested.)

It is a pain to remove the Alternator but if it Bench Tests OK there is a good chance you have a Wiring issue.

Unregulated or regulated it still needs to get electricity from the Battery some how.

[funola]

try tightening the belts then report back with your readings!

[layback40]

Originally Posted by Brian Carlton

I know where you're going with this but it has been established that these vehicles don't need that light to charge.

In fact, right at the moment, the light on the SD is non-functional and it makes that circuit via another source. It takes about 1100 rpm to do it, however. It's an interesting circuit with a small resistor within it.

Please provide some factual justification for this statement. You could just have residual magnetism providing the initial excitation.

[marybeth]

Thanks for all your suggestions. I put in the new bosh voltage regulator and had Alternator tested out of the car. Tested out at 14V at local Auto Zone.

I do not recall seeing a little charging lite-but I read voltage on the small blue wire from the Alternator to the "black box" connection in front of the battery tray.

Wiring seem to test out from alternator blade connector to "black box" to battery, no shorts or opens.

Got me scratching my head

[mbdoc]

Have you tried unplugging the GLOW relay with the car running??

It could be staying on & using all of the available POWER!

[Brian Carlton]

Originally Posted by layback40

Please provide some factual justification for this statement. You could just have residual magnetism providing the initial excitation.

The justification is in the wiring diagram for the light. You have that FSM, of course?

[kerry]

Originally Posted by mbdoc

Have you tried unplugging the GLOW relay with the car running??

It could be staying on & using all of the available POWER!

X2

[funola]

Originally Posted by mbdoc

Have you tried unplugging the GLOW relay with the car running??

It could be staying on & using all of the available POWER!

He reported (11.8 at idle 12.7 reved). In my experience, the alternator is incapable of 12.7 v reved with glow plugs on, it may make 11 to 11.5 v, not 12.7.

[Diesel911]

Originally Posted by marybeth

Thanks for all your suggestions. I put in the new bosh voltage regulator and had Alternator tested out of the car. Tested out at 14V at local Auto Zone.

I do not recall seeing a little charging lite-but I read voltage on the small blue wire from the Alternator to the "black box" connection in front of the battery tray.

Wiring seem to test out from alternator blade connector to "black box" to battery, no shorts or opens.

Got me scratching my head

I can't figure out your trouble shooting Plan.

The below is done with the Engine not running.
If you remove the Alternator Connector and you do not have nice clean connections the connections should be cleaned.

when you look at the Connector you see 2 slots that are the same size. Those 2 solts go to the Fat Red wires and both will have Battery Voltage all of the time.
The single Smaller Slot goes to a Blue Wire. That Blue Wire goes to the Charging Light (no charging light) and somewhere it goes through the Ignition Switch.
With the Key off you should have no Voltage from the small slot. With the key on and the Engine not running you will have slightly less than Battery Voltage.

Concerning the Charging/No Charging Light. When you turn your Ignition Key to the first position all of the Warning Lights should go on. That is a test to see of the warning light Bulbs are good. All Cars I have been in that use Warning Lights do that.
If the Charging/No Charging Light did not come on during that test pull out the light Bulb and replace it.

All of the sources I have read say that you need to have that Light Bulb (resistance) in the Alternator Circuit to cause excitation in the Alternator to Charge. If the Bulb is burned out the circuit is broken and in theory the Alternator is not supposed to start charging.

Notice when I made the Alternator Test Cord in the pic I included a Light Bulb to provide the proper resistance so the Alternator would charge.

Also the Alternator needs to be grounded well to the Engine Block, Chassis and the Battery.
With all of the Rust that goes on it is easy to imagine that some where it is possible the Alternator Housing is not getting grounded well.

Some people have used one Jumper Cable connected to the negative Battery Terminal and other making contact with the Alternator Housing to see if it the Alternator will start charging.

Some have even added a seperate Ground Wire for the alternator itself.