Windshield wipers start working even when the switch is off

  • 1 POST
  • 2.6L
  • 4 CYL
  • 2WD
  • 130,000 MILES

Would occasionally experience "ghost wiper" incident. One day, activated wipers and when the switch was put into off position, wipers would not shut off. Had to pull the fuse to get them to stop in the park position. Initially, tried moving different relay fuses around but that did not stop the issue. Tried replacing the two involved relays with new, still not resolved. Further reading suggested faulty motor. Replaced it. Switch activates wipers, but only get two speeds, low and high, no intermittent, and will not stop unless ignition turned off. If I wait ten or more minutes, the wipers will not come on until switched on, however, if I turn the ignition switch back on immediately, they will resume.

Do you
have the same problem?
Tuesday, December 6th, 2016 AT 1:33 PM

1 Reply

  • 29,768 POSTS

Unfortunately for car owners, the insane engineers can no longer design a system without using an unnecessary, complicated, unreliable computer. You've listed two different common problems, and both are caused by those computer controls.

The "phantom wipe", as the service bulletin called it, is solved by replacing the multi-function switch. Instead of the trouble-free wiper switch with two or three sets of contacts, everyone ow uses a variable resistor, similar to a throttle position sensor, or a volume control on older tvs. When you turn the knob, the movable contact picks a voltage from that sensor corresponding to the speed you've selected. The Body Computer sees that signal voltage and interprets that to determine the speed to run the wiper motor. In this case, "off" is not 0 volts. "Off" equates to, ... As I recall, ... About 0.75 volts. My numbers are probably wrong in this sad story, but they will illustrate my point. The lowest delay setting is about 2.0 volts. When the supplier built the multi-function switches, there were some tolerances in the sensor readings. There always are small variations in every sensor, but in this case that could not be accommodated by the Body Computer. If your switch sends a signal voltage of 1.30 volts in the "off" position, is the computer going to interpret that as "off" or the lowest delay speed?

As a point of interest, there are three part numbers on the multi-function switch assembly. One is Chrysler's number. One is a Toyota number. I don't know the third manufacturer that uses this part. I used to have about two dozen old switches that I had replaced for this problem when working at the dealership.

The second problem is the wipers staying on. Most commonly they would run on the lowest steady speed any time the ignition switch was turned on. Your description is a little different, but is still one way the Body Computer can fail. Some people cut the wire going to the wiper motor, then installed a separate switch so the wipers would never run when they weren't supposed to. The problem with that is you ended up with only high speed when switched on, and you could no longer select the low speed or any delay speed.

The advantage of using that add-on switch was you avoided the cost and frustration of replacing the Body Computer. That computer sits ahead of the parking brake assembly, on the firewall. It is extremely difficult to even feel the three bolts that hold it in, let alone remove them. To add to the misery, there was a huge plug on the bottom, and the computer plugged into another huge plug up on top. That top plug was totally inaccessible for troubleshooting. This was a really poor design, and totally out of character for Chrysler.

If you want to solve this the right way, replace the Body Computer first, then wait to see if the phantom wipe is still there. Your old computer might see 1.30 volts as the lowest delay speed, but the new one might interpret that as "off". If there is just enough differences in the computers' internal circuitry, you may not need to replace the multi-function switch.

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Wednesday, December 7th, 2016 AT 5:58 PM

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