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Alternator redux

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MadRiver

MadRiver

Jedi Knight
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Greetings all! So, I actually found a correct replacement rebuilt alternator for my 250. I also installed a new battery at the same time just to make sure that everything was taken care of.

So here's my *new* issue. Since installing the new alternator, my ammeter remains exactly between C and D when I'm at idle, but moves towards C as rpms increase. So, when I'm driving, it moves from the midpoint towards Charge as rpms increase. I also noticed that my turn signals blink more rapidly as my rpms increase. Does that sound like my voltage regulator is toast?

Thanks as always!
 
An alternator should charge the same at idle as at higher rpm. Those out there with electric fans and driving lights will attest that whenever these items are turned on, the engine idle will drop as the alternator takes up the extra load.

I have seen the problem you describe occur when the drive belt is not properly tightened. So check that first.

Else there is a problem with the the wiring, the alternator regulator, or the alternator itself.
 
you are fine as long as when the battery is fully charged it stops going too far into the C range. If it never stops then you may wish to check your charge voltage to make sure you are not at too high a voltage and boiling your battery dry.
 
I believe the only true way to be sure the regulator is not over/under charging the battery is to connect a voltmeter to the battery directly and see what the regulator is supplying at varying rpms. Obviously if the needle points to C the alternator is working. Not sure but I think the regulator in a 250 is of the non adjustable type and a new regulator will be required if the voltage output is too high or low. This sounds high to me but if the voltage input at the battery terminals at lets say 1500 rpm exceeds 16.5 volts the regulator is probably not regulating or cutting out. I think the high end of the charge is suppose to be 14.5 to 15 volts max. Apparantly your alternator is working OK but your regulator may not be regulating (cutting out) and maintaining the 12.5 to 14.5 voltage setting required to keep the battery charged. If you continue to operate at a higher voltage than required you will cook your battery (very ugly scenario). I would do a multimeter voltage test to make sure. If you need to know the multimeter settings and hook up for testing voltage output let me know.
 
Thanks guys. I really appreciate it. Harry -- I would really like to know the proper settings and hookup for my multimeter, please.

Thanks again!
 
The following from Bentley
Lucas 15ACR ( I beleive is in the 250's) & 17ACR
The idiot light should go out between 550-700 rpm
Voltage at 2200-2900 rpm should be steady at 14-14.4 volts if not indicates a bad regulator

The Delco Remy DN 460
If the voltage fluctuates with speed and exceeds 15.5 volts indicates a bad regulator
This alternator should have a steady voltage below 15.5.

These tests are with the voltmeter across the battery.

Other tests to check the output require a test setup most of us do not have.
 
TR6oldtimer is correct it is measured across the battery.

Multimeter black wire (-) probe lead to negative post on battery or good negative ground (best directly on battery though). Red (+) probe lead wire to positive post on battery. Set multimeter dial to DC VOLTS at a settimg on the dial at or higher than 20 volts. Just in case you are overcharging I would start at 50 volts and lower to 20 volts just to make sure it stays below 20. Your initial reading with the car off should be 12.5 to 13.5 volts depending on condition of battery. Start car up and observe voltage reading with running, this should be between 14.5 and 15.5. Bring rpm up as TR6oldtimer
says and observe reading it might even go as high as 16 volts but any higher and I would say your regulator is not cutting out. Over 20 Volts and you are cooking your battery. The following picture is of a very inexpensive $9.97 Sears digital multimeter. If you do not have a multimeter you want to buy a digital. Note the leads are just pushed into the space at the battery terminals. The setting is 20 volts DC and the voltage reading with the car off is 13.5 volts. My car is positive ground so do not get confused by the lead positions in relationship to the car. It's red to positive and black to negative always. Well almost always but thats another story. Good Luck!

multimeter101batterytest.jpg
 
Thanks guys, I'll try it today. I did hook up my battery charger to the battery yesterday, and though not has precise as my multimeter, the battery charger did indicate that the new battery is at full charge, so I'm thinking voltage regulator, but we'll know for sure this evening.

Thanks again!
 
Greetings all:

I did hook up my multi to the battery this morning, and I'm reading between 16 and 20 -- so I'd have to say that my regulator isn't cutting out. Then I tried the new regulator I got from Moss and observed two things:

1. When the new regulator is hooked up, the ignition light is on, even when the key isn't in the ignition. That's a new one for me.

2. I'm still reading between 16 and 20 at the battery, and my ammeter is between the middle and charge.

So, I assume the replacement is also a dud, and I hooked up the old one, turned on the lights, heater and radio and drove to work, and that kept me right above the middle on the ammeter for the most part.

I'm going to order another regulator and see if that takes care of it. Could the problem be anywhere else? I'm usually used to not enough electrical power, not too much! Perhaps I'll have to install fog lamps next...

Thanks guys!
 
Check the wire going from the "B+" terminal on the voltage regulator to the connection on the starter solenoid where the positive cable from the battery connects. That should be the remote sense wire for the regulator. If that wire has no continuity or somehow has a bad connection, the alternator will overcharge.
 
[ QUOTE ]
Check the wire going from the "B+" terminal on the voltage regulator to the connection on the starter solenoid where the positive cable from the battery connects. That should be the remote sense wire for the regulator. If that wire has no continuity or somehow has a bad connection, the alternator will overcharge.

[/ QUOTE ]

I'll check that tonight. I also noticed that the +, - and Field blades on the new regulator did not line up with the markings on the old regulator, which confused me. Does anyone have thoughts on that one?
 
Ok - I learned something I never knew from a similar thread here the other day about an internal diode in the alternator failing. The light was staying on with the key out engine off and the light went out with the engine running. His car was overcharging as well but due to the alternator diode failure and not the external regulator. I saw this post about the same time as yours so it should be close by but he changed out the alternator and all was well. Prior to replacing the alternator his heater was running faster and lights got brighter as rpms increased. You may want to have the alternator tested.
 
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