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Electrical: Engine Starting, Charging
Alternator Not Charging. When the battery loses charge and the alternator
appears not to be charging, here are some diagnostic tips:
Diagnostics. [Response: Danny Halamish] It sounds like it's probably the charging
system. Here's what I would check (in this order):
Battery terminals - clean? Good connection? Corrosion?
Alternator (thick) wires - both plus and ground (if fitted) - make sure they are
OK.
Alternator
Harmonic Balancer: the alternator belt runs off the balancer. If the rubber
insert deteriorates, the balancer shell will slip
If all that checks out OK, I would suggest you get a volt meter, and when the
voltage reads a little low, measure at the alternator: It should be 14.4V. If it's
much less, rev it up a little - does the voltage go up? If not, there is a problem.
Also, with the engine running and the voltage low (i.e. when the problem happens)
measure the following:
1. Voltage between the alternator power terminal and the battery + terminal
should be well under 0.2V
2. Voltage between the alternator body and the battery "-" terminal should be
well under 0.2V
3. Voltage between the battery "-" terminal and the engine
block should be well under 02.V
Voltage Regulator. If all this checks out but you still have a
problem, the
are two screws holding it into your alternator. You don't even need to pull the
alternator. Remove it and you'll probably find the two brushes (two black square
spring loaded shafts) worn out. A good electrical shop can replace these, or a new
regulato rfor either Bosch or Nippon Denso alternators is about $60. Install and,
get a boost and happy motoring.
[Testing Bosch voltage regulator on 7xx/9xx cars: How can you tell if your voltage
regulator has gone bad?. What tests can you do?
[Answer:] The real purpose behind the regulator is to keep the battery voltage
from getting too high. When my regulator went bad, voltage would increase with
engine speed, going as high as 18-20 V. You can easily test the regulator function
by using a voltmeter to test voltage between your battery and ground while the car
is running. Look for voltage between 13.8 and 14.6. If your voltage is higher than
this, you probably do have a bad regulator. Check the integrity of the regulator
diodes on a Bosch alternator by using a multimeter to measure the voltage
readings at the D+ terminal and B+ terminal. The voltage reading should be the
same at both terminals. A difference of more than one volt would indicate faulty
diodes and the need to replace the regulator unit. [Rick Ledbetter] Test the diodes
by disconnecting one of the D+ or B+ leads on the regulator and connecting your
probes: black is ground (use the alternator case for ground) and red is touched to
the D+ and B+ terminals. At the component level, diodes will only conduct one
way. They have to be tested out of circuit, so one lead has to be disconnected from
file:///C|/Users/Steve/Documents/Volvo%20FAQ%20Updated/ElectricalStarting.html[01/13/14 10:02:47 PM]
brushes
- if they are nearly dead, this can cause this.
alternator voltage regulator
may be defective. There
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