Alternator Charging Help...

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KP

KP

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Last year about this time I had to replaced the alternator in my 71 Duster because the battery was not charging and the factory alternator gauge showed it was not as well. I had both the battery and the alternator checked and the alternator showed to be bad. After replacing the alternator with a “new one” the alternator gauge show it was charging.

I just went out today to get my Duster ready for a small High School car show tomorrow and found the battery to be very low (cranking show) and the factory alternator gauge showing the alternator not charging again.

Any suggestions, can I use a meter to check the charging out-put of the alternator and if so on what bolts/contacts do I check and what should the display read?

Thanks For Any Help!
 
put the pos of ,meter on the big wire...should read 14.6 or so when running....did you try a new voltage reg......and make sure voltage reg is grounded
 
If it ends up being the Alternator again, what could be taking them out?
 
Following are the reading I got with my meter.

With the engine not running and all wire connected to the Alternator:
The large wire read 13.6 (Feed back from the battery I assume)
The two small wires with slide on ends read 0.0

With the engine "running" and all wire connected to the Alternator:
The large wire read 12.8
The two small wires with slide on ends read 13.8 & 14.0

With the engine "running" and the large wire disconnected from the Alternator:
The large wire "post" read 5.9
The two small wires with slide on ends read 13.8 & 14.0
 
run the engine and disconect the neg side of the battery and see if it dies. if it does die test the alternator at the store if its good replace the voltage regulator. on your 2 pole alternator one is a ground use a multimeter set on continuity and test and find wich side is the ground and trace the ground and make sure it is a good ground also.
 
those numbers dont sound right.the large wire on the alternator and the battery positive should be at the same potential and the field wires should not be the same.try this for starters to check a couple things.start the car and put the test meter on voltage. put the negative test lead on the battery negative and the positive test lead on the alternator case.this checks for bad conections.you should have very little voltage. maybe a couple tenths. now do the same test frome the battery positive to the alternator large post.thats the one im suspicious about because you had different voltage readings.if you show anything let me know what it is
 
you gave two different voltages for alternator post with moter running witch is it. If all those steps check ok on the power circiut the next test is to bypass the regulator to verify alt or reg bad.
 
to force the alternator on unplug the green wire and ground that field spade on the alternator it will charge full if its any good.
 
could the amp guage wires have come loose?

i would ground the one fld wire like stated and see if it charges.

regulator could be on the way out also.

may be a good idea to cheack all the connections including the bulkhead to see if they are corroded. i know i was surprised when i saw my bulkhead connection all greem.
 
I've heard those old amp gauges are really crap? Does the charge go through the guage? I've heard it does. i've disconnected mine and went to a standard voltage guage.
 
I thank everyone for their help and just want to make sure this is understood.

I took all measurements with a multimeter

I know the old dash gauges are not all that reliable but the battery is not being recharged (battery is good)

With the engine "running" and the large wire disconnected from the Alternator The large wire "post" only reads 5.9
 
folow the checks in order. when you put the meter from the alt post to the positive with the motor running it checks the amp gauge con. plugs and wires in between.if it shows voltage then, thats voltage lost its broke.do the checks before you jump the alternator, you have to have good wireing before the alternator can charge.
 
yes abody joe all that stuff could be bad.If it is the volt meter will tell you but you have to test it under load to see it
 
If I disconnected the large wire from the Alternator and start the engine then use my multimeter to check how many volts are at the post where I removed the large wire what should the reading be?
 
ground the little spade on alt, closest to the big wire..just touch it to the engine......That is what fixed mine
 
sorry, spade connector.......A spade connector is what is on the back of speakers for your car, that the little wire hooks to......if you pull the center wire off you will see what I mean
 
chasduster said:
sorry, spade connector.......A spade connector is what is on the back of speakers for your car, that the little wire hooks to......if you pull the center wire off you will see what I mean
Click to expand...

Can you take and post a photo please.
 
KP said:
Can you take and post a photo please.
Click to expand...


There are 3 wires on the alt correct?????????Take the middle wire and pull off the alternator......make another wire and hook it to the middle terminal on the alt....and touch the other end of it to ground with it runnin....does it charge???????????
 
chasduster said:
Did you try this......due you still need a pic of it
Click to expand...

Sorry I did not do this yet. Yesterday was a sad day for me, it was one year from the day my dear mother past from this life.
 
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