In attempting to troubleshoot a malfunctioning ECC, I have been pinning out, checking for continuity, and generally trying to understand the whole HVAC system. Progress is being made since 2 of the 4 shutter motors work, and the REC shutter works. However, the REC and AC light still blink during startup.

Based on help from others on this forum, I've:

1) cleaned and verified operation of both cabin air temperatures (behind the grab handles on the passenger and driver side).

2) located 3 duct air temp sensors (all 3 checked for operation and seem ok).

For the air temp sensors a multimeter was helpful. All seemed to measure aroud 7 k-ohm at the temperature in my garage, and resistance fell when exposed to the warm exhaust of a hair drier. So, I think the ones I've located are working.

However, on one of the connector blocks to the ECC where the three duct sensors connect, there appears to be a 4th wire. It does not show similar resistance to the common wire.

Here's my question: DOES ANYBODY KNOW IF THERE'S A 4TH DUCT SENSOR SOMEWHERE?

Thanks for the help.