GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Inspection & Testing

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HIGH VOLTAGE SWITCH INSPECTION



  1. Visually inspect the HVS cap for cracks or tiny holes. Replace the cap if it is damaged or worn.
  2.  
  3. Check the metal terminals in the cap for corrosion. If any corrosion is found, scrape the terminals clean with a suitable scraping tool or replace the cap.
  4.  
  5. Inspect the HVS rotor for wear or burning at the outer terminal. A build-up of carbon on the terminal means the rotor has worn and needs to be replaced.
  6.  
  7. Check HVS shaft for shaft-to-bushing looseness. Place the shaft in the housing. If the shaft wobbles, replace the housing and/or shaft.
  8.  
  9. Visually inspect the HVS housing for cracks or damage.
  10.  

IGNITION COIL TEST



See Figures 1 and 2



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Fig. Fig. 1: HVS ignition coil testing-1995 4.3L (VIN W) Engine



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Fig. Fig. 2: Ignition coil testing points-1996-99 models

If the trouble has been narrowed down to one of the components in the ignition system, the following test can help pinpoint the problem. An ohmmeter with both high and low ranges should be used. This test is made with the negative battery cable disconnected.

  1. Disconnect the high voltage switch lead and the wiring from the ignition coil.
  2.  
  3. Set the ohmmeter to the HIGH scale, then connect it to the coil, as shown in Step 1 of the appropriate illustration. The reading should be infinite. If not, verify a proper test connection to be assured of a true test result and if still not infinite, replace the coil.
  4.  
  5. Set the ohmmeter to the LOW scale, then connect it as shown in Step 2 of the appropriate illustration. The reading should be very low or zero. If not, verify a proper test connection and replace the coil.
  6.  
  7. Set the ohmmeter on the HIGH scale, then connect it to the coil as shown in Step 3 of the appropriate illustration. The ohmmeter should NOT read infinite. If it does, verify the connection and replace the coil.
  8.  
  9. Reconnect the high voltage switch lead and wiring to the coil.
  10.  

 
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