Coolant fluid low / Windshield fluid low permanent on the dashboard
Thread Starter
Newbie
Joined: Apr 2020
Posts: 7
Likes: 1
W209 2003
Coolant fluid low / Windshield fluid low permanent on the dashboard
Hi everyone, I need help diagnosing an issue with my Mercedes CLK (W209).
The coolant level and windshield washer fluid level check messages are permanently displayed on the dashboard.
A while ago, I unplugged the windshield fluid sensor since it didn’t trigger any warning even when empty. The sensor’s board looked fried, and a multimeter showed no resistance, unlike a new one which shows 180Ω.
After removing it, both messages for the coolant and windshield fluid are displayed permanently on the dashboard and won’t clear, even after replacing the broken sensor.
Here’s the strange part:
Neither sensor’s connector has voltage, even with ignition on. On my dad’s W203 (same wiring and parts as W209), they get 5.5V.
Looks like the SAM isn’t supplying power to the sensors. Why would that be? Can I supply 5.5V externally? Could it be a relay on the SAM I can replace, or is this a deeper issue?
I’m stuck and would appreciate any ideas.
I have attached a wiring diagram below.
The coolant level and windshield washer fluid level check messages are permanently displayed on the dashboard.
A while ago, I unplugged the windshield fluid sensor since it didn’t trigger any warning even when empty. The sensor’s board looked fried, and a multimeter showed no resistance, unlike a new one which shows 180Ω.
After removing it, both messages for the coolant and windshield fluid are displayed permanently on the dashboard and won’t clear, even after replacing the broken sensor.
Here’s the strange part:
Neither sensor’s connector has voltage, even with ignition on. On my dad’s W203 (same wiring and parts as W209), they get 5.5V.
Looks like the SAM isn’t supplying power to the sensors. Why would that be? Can I supply 5.5V externally? Could it be a relay on the SAM I can replace, or is this a deeper issue?
I’m stuck and would appreciate any ideas.
I have attached a wiring diagram below.
Junior Member
Joined: Aug 2023
Posts: 42
Likes: 8
From: Whitecourt Alberta Canada
2007 A209 CLK 350
The first thing I would check is the connectors. If they get corroded inside they can cause all kinds of issues. It is possible that something in the connector broke when you removed it and is no longer making a circuit.
