Dash temp light flashing, radiator fans cycle fast/off
My 2003 GLS 1.8T flashes the thermometer light when I first start it every morning during cooler months. It will continue to flash unless I restart it after it has been running several minutes and warmed up.
The heat and A/C work fine
Coolant level is fine
The engine temp gauge rises as expected and stays at center (190)
The car has never overheated
Both upper and lower radiator hoses get hot
Recently had timing belt, water pump and thermostat replaced
I recently replaced the secondary air injection (SAI) blower and it works fine
There is no CEL.
Both radiator fans work but are off most of the time and never spin "slow".
Every few minutes they spin up high, run for several seconds and shut down again. It dims the headlights when it does this. This seems to occur more in the summer when the A/C is on, and if I turn the A/C off when they are spinning fast they shut off immediately. I don't know if it ever happens when moving, I only notice when sitting at a stoplight or just idling in the garage. With A/C off, the fans still cycle on and off, but at a much lower frequency, about every 5 minutes (garage temp 50F).
I think the dash light on cold starts and the fan cycling are separate and possibly unrelated issues because the fans cycle whether the dash is flashing or not. From what I have seen, the fix for the dash light is a whole new $215 overflow ball (or a piece of black tape). I added about a half pint of distilled water and re-seated the connector and it seems to be better. Will see tomorrow morning.
Since both fans work, it would seem the control circuit is faulty. My research indicates it is likely:
The fuses or holder on top of the battery (they look fine)
The fan control module T14, located under the battery
The coolant temperature sensor (don't know if mine is green, where is it?)
I've read that shorting the pins 1&2 on the FCM while the ignition and A/C are on (car not running) will force the fans to run slow and jumper on pins 2&3 will run them fast. Not sure how to do this since I think I need to remove the battery in order to get at the FCM.
Any help is greatly appreciated.