How to Diagnose your BMW E30 Windshield Wiper Motor System

Hey YT-

I, sir bimmerdaddy, thought I'd bring you along as I diagnosed why my hoopty E30's wipers were not working. A digital multimeter is required for diagnosis.

Key must be in accessory position for testing
The following testing is done with the K10 wiper relay removed from the E30 fuse box

Test #1: Check to make sure you have power at the wiper relay by checking voltage between pin 15 and ground (pin 31 or suitable chassis ground).

Test #2: Make a jumper and jump pin 15 to pin 53. This tests the low speed operation of the wipers. If you jump pins 15 and 53 and your wipers DON'T function, this more than often means that you have a bad wiper motor.

If you jump these pins and the wipers DO function, this more than often means you have either a bad column switch or wiper relay, and can test further via the additional steps below.

Test #3: To test the washer fluid motor, jump pin 85 to ground (pin 31 or any suitable chassis ground).

If both the wiper motor and washer fluid pump works you can test the column switch more acutely by doing the following:

#1 - Put your multimeter in continuity mode and check for the magical beep between pin 31 and ground. If you don't get continuity here, check the g100 ground location under the dash (shown in video) and also check the ground on the front of the steering column at the wiper switch itself.

#2 - Test the high speed of the wiper switch by putting the wiper switch in the high speed position and testing for continuity from pin FII to ground (pin 31 or any suitable chassis ground).

#3 - Test the low speed of the wiper switch by putting the wiper switch in the low speed position and testing for continuity from pin FI to ground (pin 31 or any suitable chassis ground).

Hope this helps!