Windscreen washer control issues - possibly BCM?
 

Hi from the UK. I have a 2006 Chrysler Grand Voyager 2.8 CRD and I have a really weird fault! The windscreen washer pump either pumps to the rear screen or the front screen and it switches polarity feed to the washer pump depending on whether feeding front or rear. It works fine when I turn on the ignition, but after I start the engine and engage Drive it usually fails after a few seconds.....whether requesting demand for front or rear screens! Turn engine off and reengage ignition and all works fine again. So I have checked and it's not the pump that's faulty. Measuring voltage at the pump connector verifies that despite demand, no voltage is presented to the motor after a short while after Drive is engaged. I am electrically competent, and have cleaned the relevant connector up at the TIPM (having traced the wires back from the washer pump). So I am thinking I either have a TIPM or more likely perhaps BCM issue but I don't have wiring diagrams so I am reaching stalemate. I am even considering a bypass circuit to run the pump....is anyone able to offer a wiring diagram for the front washer switch so I can maybe bypass the BCM and install a relay to drive the washer pump p[lease? Thanks in anticipation!

So......I am answering my own question here in order to maybe help others! This is a real bizarre one! I have previously performed the “Leedsman” button modification to increase the charging voltage on the battery. Subsequent to that I still ended up having to replace a poor performing battery. It turned out that once I had the replaced the battery, the voltage when the alternator is fully engaging gets as high as 14.55 Volts. I noticed that if I turned on the headlights and heated rear windscreen etc this pulled the voltage down by circa 0.3 Volt and hey presto the washer pump started working again! So I backed out the modification and instead of using a 33KOhm resistor, I replaced with two 33KOhm resistors in parallel (16.5KOhm) to ensure the charging voltage doesn’t exceed 14.3V. Now washers perform fine! So I suspect the BCM is sensitive to over voltage….who knew!!!??🤷🏻‍♂️
Hope this helps others!
Peter