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Discussion Starter · #1 ·
My cars battery always dies and runs at to low of volt (12.5) when the cars on, I went to advanced auto and they tested my alternator, regulator, and battery, and everything comes out fine! what could be draining my power???????? Conections on the alt. are fine....what else?
 

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Discussion Starter · #3 ·
new battery, car is driven alot.
 

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Well, if it's not dieing from sitting, see what the alternator is putting out. Measure the alternator red cable (B+) to ground with the car at idle. What do you read? Measure across the battery terminals with the car at idle. What do you read?
 

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Discussion Starter · #5 ·
Havent checked B+ to ground yet, but accross the terminals Im at 12.5 at idle......Shouldnt I be like around 14.5?
 

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Discussion Starter · #7 ·
ok i checked, B+ to negative is 12.3!!!! any other ideas?
 

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Well, the system is not charging so something must be wrong. Try this info;

I'll try to provide a simplified explanation of how the externally regulated alternator and regulator work here. This explanation starts from a parked car with engine off state.

The brown #4 wire is connected through the light bulb to 12V whenever the key is in the ON position. The other end goes through a set of points in the regulator and then out the F terminal to the field winding in the alternator. So some current begins flowing in the field winding from this connection. The little bit of current flowing produces a weak magnet field in the alternator and also lights the bulb.

When you then start the car, the weak magnetic field from above begins rotating which makes the alternator producing a little bit of voltage. This voltage is fed from the alternator to the regulator on the white #2 wire. This wire connects to a coil in the regulator and turns on a contact when the voltage goes above 3.2V.

Once the contact turns on in the regulator the #3 and #4 terminals are connected together. Terminal #3 is battery power so this puts battery power on both sides of the bulb and turns it off. This means the brown #4 wire should go to +12V. Also, this connects the field terminal right to battery power but still going through the points.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the points I kept mentioning. Then the voltage drops and the points close again. This on-off cycling happens rapidly and is how the voltage gets regulated.

From the above (KOEO = key on engine off and KOER = key on engine running).
F terminal - KOEO = #4 slight voltage KOER = 9-12V typically
#2 terminal - KOEO = 0V KOER = >3.2V
#3 terminal - KOEO = 12V KOER = 12V
#4 terminal - KOEO = F slight voltage KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but should be 14V when engine is running.

Check the brown #4 wire by grounding it at the regulator. When grounded the light should come on. If you don't have a light then skip this test. Test this with the connector off the regulator.

Jumper the blue wire F terminal to the battery right at the alternator connector. This should make it crank out 16+ volts. If it passes this test, jumper wire the brown wire (#4 of the regulator connector) to the same F terminal and you should be able to measure >3.2 volts on the other alternator terminal. If these tests pass, it is in your regulator or the wiring to the regulator.

If you know for sure the wiring is good then try getting another regulator. The first one I purchased wasn't the right one but it looked correct and fit right. At least thats what the parts guy though but at any rate it was either wrong or didn't work.

Peter
 
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