Wiper failure on STS-99

[Jonny Wallin]

Hi all! To add my problems with electrical problems. Suddenly my windscreenwiper and washer is stone dead. I have checked the fuses and measured and have voltage to the wiper-engine. It looks like there is a electrical card inside? Have someone done investigation of this and can give me some advise to solv this problem.

Regards Jonny Wallin from Sweden

[SwampeastMike]

Two different fuses for the windscreen wipers. Both in the underhood block. Fuse #2 (10A) is for the control system and fuse #3 (30A) for the wiper motor intself. Main power to the wiper motor is supplied anytime the ignition key is at "ACCY" or "RUN" with various low-level operation signals from the switch and Rainsense (auto) wiper sensor. Fuse #2 (labeled in the owner's manual as "Accessory") is for the w/w switch, Rainsense control and the cell phone docking station (in the center console). Wiring for the docking station is there even if you don't have the phone. Yes, there's an electronic module in the wiper motor, and it [seems] to be part of the motor cover and [should] be available as a separate part.

Presuming the wipers AND washers do not work in ANY switch position, here's some abbreviated instructions from the service manual. (Considering the problems you're having, I'd really suggest you get a copy or at least an on-line subscription.)

Set ignition key to "Run" and disconnect the wiper harness connector at the motor.

Step 1: Connect a test lite between terminals B and C on the connector side. (This is the yellow wire and the black wire next to it on the SAME row.)

If the test lite lights in Step 1: Set wiper switch to "high" and connect a test lite between terminal H (dark blue) and ground. If the lite lights, replace the wiper motor cover (it's simply attached with three screws). If the lite does not light, again check "Accessory" fuse #2. If fuse is good, check for an open circuit in #43. Circuit #43 is a yellow wire running from fuse #2 through the smaller (lower) firewall penetration at the right front of the engine compartment. It then runs to an 18 cavity connector in the left rear of the passenger compartment near the rear shelf at the base of the sail panel (sail panel is the rearmost upper trim panel and finally to the rainsense sensor near the inside rear view mirror. It ALSO runs to C202 at the base of the steering column. If the circuit is good, replace the wiper/washer switch.

If the test lite did NOT light in Step 1: Connect test lite between terminal B (yellow wire) and ground. If it lights, repair open ground circuit 150 (black wire). It runs from the connector to a ground distribution block located in the center left of the engine compartment beneath the air inlet hose from the air cleaner to the engine. If it doesn't light, verify that fuse #3 (WSW) is good. If fuse is bad, disconnect the BROWN underhood fuse block connector and check resistance of terminal F3 to ground. Terminal F3 has a yellow wire and is at the bottom of the connector. The bottom has two little tabs, the top only one on the right. F3 is the third from the left. Resistance should be below 0.5 ohms. If resistance IS below 0.5 ohms, find the to short to ground in circuit 150; if greater replace the windshield wiper fuse #3. If the fuse is good, repair open in power circuit #143 running from fuse #3 to the wiper motor.

A bit hard to condense a flowchart, but did my best. Note that "replace wiper motor" is NOT included. This is because the first step in wipers not working in any position is: operate washer. If washer works, replace wiper motor.

[Jonny Wallin]

Hi! Thanks for your good explanation SwampeastMike!

Today I solved the problem. The failure was a rusty bad earth point under the air-cleaner. I cut all cables and maked a new frech earth pont, and it works great. I understand the failure when i mesured from battery-plus to earth on the wipermotor, and the lamp did´t light up.

[SwampeastMike]

Hi! Thanks for your good explanation SwampeastMike!

Today I solved the problem. The failure was a rusty bad earth point under the air-cleaner. I cut all cables and maked a new frech earth pont, and it works great. I understand the failure when i mesured from battery-plus to earth on the wipermotor, and the lamp did´t light up.

That's ground circuit 101 for the windscreen wiper motor, cruise control module, underhood lamp, engine coolant level switch and brake fluid level switch. Thought of that ground connection first, but you didn't mention a "Check Coolant Level" message that should have appeared quite rapidly. Unfortunately it would not seem to have anything to do with the EBTCM problem. Have you pinpointed that yet?

[Jonny Wallin]

Hi! Thanks for asking. But first a answer on my fault finding. The only cable that did not "have ground" was only wipers in circuit 101. Thats why I have longer way for faultfinding. It was good to know what equipment the other oxidated "grouds" support. I appreciate your work to help me.

I have still not solved the other problem with EBTCM.

I have dismunted all fuses in front & rear fuse boxes and put in new ones with a little oil CRC 556 in the bottom of the metal. I have only drive a short drive and I did not see the message.

I still hop. But my experince of life is that, I´m not the "lucky guy" with this type of problem.

[pizza442]

Hi, reviving an old thread. Have a 2000 SLS with same symptoms. Looked at ground under air intake box. Didn't appear rusty or corroded, a little dust/road dirt. Disassembled connector and pulled all wires out to inspect. Also used crocus cloth to clean up mount point on body. Blasted and dried wd-40. No go.

Low Coolant light DOES come on. SES light is on too. No wipers at any speed or washers. No visible corrosion at crimp points on wires. Will try to get fella with test light to check on Mon. but thought I would ask for feedback here first. Scan for codes at that time too.