Chrysler RAM50/D50/Arrow 1979-1993 Repair Guide

Modulator Unit

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TESTING



See Figure 1

  1. Raise and safely support the vehicle so that all four wheels are off of the ground on jackstands. Keep the vehicle as close as possible to a horizontal state.
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  3. Confirm that there is no dragging in the rear brake.
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  5. Warm up the engine.
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  7. Keep the 4WD vehicle in the 2H condition.
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  9. Keep the engine in an idling condition. In case of a manual transmission, put the shift lever in the 4th gear. In the case of an automatic transmission, put the shift lever in the D range and after depressing the accelerator pedal once, allow the engine to idle again.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: Test the resistance between terminals 1 and 2, and between terminals 3 and 4-1992-93 Pick-ups

  1. While running the rear wheels, depress the brake pedal (also depress the clutch pedal for vehicles with a manual transmission) with a force of 22-66 lbs. (100-300 N). Measure the time when the wheels have stopped running. The standard value for normal conditions is 3-5 seconds, and while the G-sensor is disconnected it should take less than 1 second.
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  3. If the G-sensor is connected and the wheels stop too soon or too late, the modulator is malfunctioning. Have the modulator checked by an automotive mechanic familiar with Mopar vehicles.
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  5. Also check that the resistance value between the terminals of the electrical connector is 4.3 ohms for terminals 1 and 2 (release valve) and 5.0 ohms for terminals 3 and 4 (hold valve).
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  7. If any of these tests is failed, the modulator unit must be replaced with a new unit.
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REMOVAL & INSTALLATION



See Figure 2

  1. The modulator unit is located under the right-hand bed of the Pick-up, in front of the rear right wheel. Remove a heat shield, if so equipped.
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  3. Disconnect the vacuum hose, brake fluid lines and electrical connectors from the modulator unit.
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  5. Unbolt the modulator bracket from the frame and remove the unit with the bracket.
  6.  



Click image to see an enlarged view

Fig. Fig. 2: The modulator unit also contains the release and hold valves-1992-93 Pick-ups


CAUTION
The modulator unit is not to be disassembled; its nuts and bolts should absolutely not be loosened. The unit must not be dropped or otherwise subjected to impact shocks. It must also not be turned upside down or laid on its side.

  1. Bolt the modulator unit back to the fender with the bracket.
  2.  
  3. Attach the vacuum hose, the two brake lines and the electrical connector. Tighten the brake lines to 12 ft. lbs. (17 Nm).
  4.  
  5. Bleed the brake system.
  6.  

 
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