Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

Voltage Regulator

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REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the leads or plug socket from the old regulator taking note of their (its) location.
  4.  
  5. Remove the hold-down screws from the old regulator and install the new one.
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  7. Connect the leads or plug socket and reconnect the negative battery cable.
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VOLTAGE ADJUSTMENT



Motorola (S.E.V. Marchal) Regulator

See Figures 1, 2 and 3

If the Motorola A.C. Regulator is found to be defective, it must be replaced. No adjustments can be made on this unit.

The following test may be performed on the Motorola regulator to see if it is functioning properly. Am ammeter, tachometer, and voltmeter are required. Note that the ammeter circuit commonly found on a volt/ohmmeter (VOM) is for very small amperages and is NOT sufficient for this test. An ammeter reading to at least 75 amperes is required.

  1. Connect the test equipment to the alternator and regulator as shown in the illustration.
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Fig. Fig. 1: Wiring diagram for testing the Motorola regulator

  1. Run the engine at 2500 rpm (5000 alternator rpm) for 15 seconds. With no load on the alternator, (all electrical equipment turned off) and the regulator ambient temperature at 77°F (25°C), the reading on the voltmeter should be 13.1-14.4 volts. For regulator ambient temperatures other than 77°F (25°C), consult the voltage-temperature diagram for cold regulator.
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  3. Load the alternator with 10-15 amps (high beam headlights) while the engine is running at 2500 RPM. The voltmeter reading should again be 13.1-14.4 V Replace the regulator if it does not fall within these limits.
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  5. For a more accurate indication of the regulator's performance, drive the vehicle for about 45 minutes at a minimum speed of 30 mph. The regulator will be at the correct working temperature immediately after this drive.
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Fig. Fig. 2: Voltage/temperature diagram for a cold regulator



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Fig. Fig. 3: Voltage/temperature diagram for a warm regulator

  1. With the engine running at 2500 rpm and the regulator ambient temperature at 77°F (25°C), the voltmeter reading should be 13.85-14.25 V For regulator ambient temperatures other than 77°F (25°C), consult the voltage-temperature diagram for warm regulator.
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Bosch Regulator (35, 55, 70 amp)

See Figures 4 and 5

The Bosch regulator is fully adjustable. To determine which adjustments are necessary (if any) perform the following test. An ammeter, 12 V test lamp, tachometer, and voltmeter are required for this test.

Where the numerical values differ for the 35 amp voltage regulator and the 55 amp unit, the figures for the 55 amp regulator will be given in parentheses.



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Fig. Fig. 4: Wiring diagram for testing the Bosch regulator

  1. Connect the alternator and regulator shown in the illustration.
  2.  

The first reading must be taken within 30 seconds of beginning of test.

  1. While running the engine at 2000 rpm, load the alternator with 28-30 amps (44-46 for 55 amp alternator).
  2.  
  3. Rapidly lower the engine to idle speed or 500 rpm and then return it to 2000 rpm. With a load of 28-30 amp (44-46 for 55 amp alternator), the voltmeter reading should be 14.0-15.0 V (13.9-14.8 V for 55 amp alternator). The regulator should be regulated on the left (lower) contact.
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  5. Reduce the alternator load to 3-8 amps. The voltmeter reading should not decrease more than 0.3 V. (0.4 for 55 amp alternator) The regulator should be regulated on the right (upper) contact.
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  7. Adjustment is made by bending the stop bracket for the bimetal spring. Bending the stop bracket down lowers the regulating voltage; bending it up raises the voltage. If the voltmeter reading for the low amp alternator load decreased more than 0.3 V. (0.4 for 55 amp alternator) compared to the reading for the high amp alternator load, adjust the regulator by bending the holder for the left (lower) contact and simultaneously adjust the gap between the right (upper) contact and the movable contact. The gap should be adjusted to 0.010-0.015 in. (0.25-0.40mm). If the holder is bent toward the right (upper) contact, the regulating voltage under high amp alternator load will be lowered. To avoid faulty adjustments due to residual magnetism in the regulator core, it may be necessary to rapidly lower the engine rpm to idle after each adjustment, and then raise it to 2000 rpm to take a new reading.
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Warm regulators may be cooled to ambient temperature by directing a stream of compressed air on them. Final readings should be made with the regulator at ambient temperature.



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Fig. Fig. 5: Component legend for the adjustable Bosch voltage regulator

1983 and newer Bosch alternators use an integrated voltage regulator. This device is mounted directly on the back of the alternator. Due to its solid state construction, no internal testing or adjustment is possible.

The function of this type of regulator can be simply tested with a voltmeter in the following fashion:

  1. Connect voltmeter between terminals B+ and D on the alternator. DO NOT disconnect any other wires on these terminals when testing.
  2.  
  3. Have an assistant start the engine and accelerate it to 3000 rpm and apply the specified electrical load. For an alternator rated at 55 amps, apply a 47 amp load. For a 70 amp alternator, apply 60 amps and for a 90 amp alternator apply a 77 amp load. This load tests the alternator at 85 percent of its rated output.
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  5. If the regulator is cold (77°F/25°C) and the reading is taken within one minute of start-up, the correct voltage should be 14.4-14.8 V for 1983 and 1984 models. 1985 and later models should show 14.1-14.9 V.
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  7. Under hot regulator conditions (car has been driven at least 15 minutes) the test voltages should now be between 0 and 0.3v lower than the cold test above.
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  9. Any readings outside these limits (either over or under) require the replacement of the regulator. This is done with the engine off by unplugging the connector (if there is one) and removing the two mounting bolts which hold the regulator.
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WARNING
When removing the regulator, a set of alternator brushes will come out with it. Don't lose any small parts. Reinstall carefully, paying attention to proper brush placement and seating within the alternator.

 
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