Power windows, radio, blower stop working Dodge Grand Caravan
If you run into a problem where these electrical accessories work when the key is turned to the RUN position but the engine is off, but stop working when the engine is running, the problem may be either the ignition switch or the intelligent power module (IPM).
Start by checking the voltages from the ignition switch when it is in various positions. With the key out, the ignition switch reports 4.6 volts to the BCM. The voltage goes down to 4.04 volts when you insert the key, 3.2 when you turn the key to the ACC position, 1.12 volts when you turn to RUN, and 0.41 when you turn to START. If those voltages check out, test the voltages at the IPM.
Check for voltage at circuits T751 and T752 at the IPM with the engine running. These circuits should have battery voltage only during engine cranking. They should go to 0 volts with the vehicle running. If there is any voltage on these circuits, the FCM will cut off power to the ACC relay, causing those electrical accessories to stop working. If you find voltage on these circuits, inspect the wiring harness, especially around the battery. Shops are reporting that battery acid can caused voltage tracking into these circuits. Another cause may be add on electrical accessories like a remote starter system.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat