TM-9-2320-280-20 HMMWV Technical Manual Unit Maintenance Volume 1 Download
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TM 9-2320-280-20-1 REFERENCE INFORMATION Dead glowplugs draw virtually no current, but other parts of the vehicle are drawing some current, up to 8 amps. If any glowplugs are drawing any current, then the protective control box is probably OK. For a good description of how glowplugs cycle and how to check for proper cycling, refer to page 2-307. WARNING Disconnect negative battery cable before disconnecting and reconnecting protective control box harness. There is battery voltage at the PCB at all times. Failure to disconnect battery cable will result in damage to equipment or injury to personnel. If most or all of the glowplugs are bad, you may also have a problem with the protective control box or the glowplug controller which caused them to go bed (usually they burn out from being on too long or not turning off at all). After replacing the bad glowplugs, rerun the glowplugs test chain paying special attention to the glowplugs cycling, especially that they turn OFF when they should. Replace glowplugs, wires, or harness, refer to (para 3-38). 1. 2. 3. Disconnect ALL the glowplugs. Disconnect the negative battery cable. Disconnect the PCB connector harness from the PCB. Reconnect the negative battery cable. Measure the resistance between pin Din the engine connector harness of the protective control box and ground. There should NOT be continuity (resistance reading off-the-scale). If there is continuity, repair or replace the harness. Repeat the following for each glowplug a. b. c. Reconnect the wiring harness to the glowplug while you repeat the resistance measurement described in step 2. When you reconnect the wire to the glowplug, the resistance should drop to between 1 and 2 ohms (glowplugs are typically 1.6 ohms). If step a passed; disconnect the glowplug again, making sure the resistance goes off-scale again. Repeat step a for the next glowplug. If step a failed; then either the glowplug or its wire is no good. Take the wire off the glowplug again and measure the resistance from the glowplug to the engine block. If the resistance is 1-2 ohms, then the cable is no good, otherwise replace the glowplug and check the cable for continuity, just to be sure. 4. Reconnect the PCB and all wires. 2-309