replaced alternator but still not working

[grasshopper]

Hi all. I have a 1970 124 Sport Coupe. The alternator was not working so I replaced it with a new one. The new one was not working so I replaced it with a second new one. My red ignition light was not coming on. However,i was messing around with the wires that are hooked up to the alternator. They are all hooked up properly but I unhooked the yellow wire with female end and accidently touched the middle power wires that are bolted onto the middle of the alternator secured with a nut. When the yellow wire touches the middle wires on the nut,my red ignition light comes on and the relay closest to the dashboard on drivers side "clicks".....what is going on here ? I need to diagnose this issue. Does it mean that the alternators that I bought are not wired properly or is it another issue ? Any help would be much appreciated.

[spider2081]

Here ia a simplified wire diagram of what I believe is your alternator circuit.



Hope this helps.
I could not find a diagram showing where each relay is located but you can identify your relays by the wire colors on the diagram.
Basic circuit operation of the light is: The light has voltage on one side of it as soon as the key is turned on. The ground for the light passes through the normally closed contact of the "battery charge indicator relay" to light the light. When the engine is running and the alternator is working the yellow wire brings voltage from the alternator to the relay coil. the relay disconnects the ground from the "battery charge indicator" in the tach. So the light goes out. The Voltage regulator supplies voltage to the alternator to control the alternators output. You should measure battery voltage on the grey wire at the alternator with the key in the "on" position. The ground for the charging system and the headlights is made at the voltage regulator mounting bolt.

[GeorgeT]

I think the charge indicator lamp must be good for the alternator to charge. Check the lamp and replace if necessary.

[grasshopper]

Thank you for the diagram and the response. However, I still need to know why the yellow wire to the alternator does not send signal to red ignition light unless you unplug the yellow wire from the alternator and then make contact with the middle nut at alternator (the one with the wire direct to the battery),,I tried to describe this in my intitial posting,,,im not sure if I'm making myself clear though ? Any thoughts ?

[DieselSpider]

The low voltage indicator should not light up unless the alternator is not working or you connect it directly to the battery terminal. Is the battery charge indicator relay connected and in working condition or possibly connected backwards?

[spider2081]

still need to know why the yellow wire to the alternator does not send signal to red ignition light unless you unplug the yellow wire from the alternator and then make contact with the middle nut at alternator (the one with the wire direct to the battery)

The wire diagram show that the power the light needs to light comes from the fuse 10 unfused connection from the ignition switch. In other words as soon as the ignition witch is turned on the light should have voltage on one side of it. It also shows the lights ground passes through the relays normally closed contacts. This completes the light circuit for the light to light. The yellow wire from the alternator has no voltage on it until the engine is running and the alternator is working. Then it has voltage on it and provides voltage to the relay coil. This makes the relay operate, opening the lights ground and turning off the light.

If what you are saying is the light lights when you put battery power to the yellow wire. I would think the relay is wired incorrectly. The diagram shows you what color wire belongs on what numbered terminal of the relay. Also if the alternator is not functioning you need to check the voltage regulator for proper wire colors on the correct terminals. For you car the alternator does not depend on a working alternator warning light to function. That is for the later model alternators with built in voltage regulators.

[grasshopper]

Ok,,I found an old relay and connected it all up. Now the red ignition light goes on when I turn the ignition key but it does not go out when the car is running. I think I have everything connected properly. Could I have an ignition switch wire hooked up incorrectly ?

[spider2081]

I would now check the connections at your voltage regulator. When you turn on the key you should have battery voltage at the orange wire on terminal 15 and also battery voltage on the grey that is on terminal 67. This grey wire connects to terminal 67 on the alternator. So with the key on you should have battery voltage on the alternators terminal 67.

[DaveMarcotte]

As per spider2081 told me. Check that the orange is connected to the fuse. On my 77 that wire is just long enough and it somehow got pulled out of the socket at the fuse. I would have never thought to check.

[grasshopper]

I checked the orange and grey wires at the external regulator with the ignition switch to the on position with the car not running. I'm not getting any power at either wire . The orange wire seems to be coming out of a cluster of wires,,,im not sure where it starts from.

[spider2081]

The orange wire should be connected to the voltage regulator terminal 15 and to fuse 10 in the fuse panel. Fuse 10 is the tenth fuse from the steering column. The ignition switch has to be in the "on" position.

[grasshopper]

I think everything is working,,yayyyyy !! I checked over everything I could think of and everything you all helped me out with. I was finally getting the red ignition light on when I turned the key but it would not go out. I visually checked all fuses and thought they were all good. I re checked the number 10 fuse as you suggested,this time taking it out and it had a crack in it that I didn't see. I replaced it and now everything seems to be tickety boo. I have not checked for voltage at the battery but I am not getting any weird symptoms happening anymore such as bouncy tack when using signal lights,etc etc. I will let you know if I have anymore problems. Thanks again for all your help !
Rob

[spider2081]

Thats great news. Enjoy the car

[grasshopper]

The car is running well but I notice when I am at a stand still with lights on,lights and dash lights go a little dimmer until I rev the engine up a bit. Is this normal ?

[spider2081]

yes this is normal for most all alternator and generator installations. The alternator shafts pulley is usually designed so the alternators maximum design RPM is mot exceeded. With higher RPM engines this means the alternator at engine idle might be turning slower then that required to have an output. So at idle the car is using the battery to operate the lights etc.
This is much better than having the alternator spin to fast at cruising speeds. It is also better for the voltage to be regulated with a maximum of 14.25 volts as more than that can over charge the battery reducing its life span. Many are designed to be regulated with 14 volts to be the maximum.