Cooling fan sequence
 

Hi All,

I have a 2003 Boxster-S with just under 50,000 miles. Before buying Boxster my hands on working knowledge on car was limited to oil change/Air filter and cabin filter. After buying Boxster and joining this community, I have been able to do lot more and learning continues.

I am experiencing that the blower in the engine compartment comes (not taking about the secondary fan that comes on when we start the car) before the radiator fan kicks in. This is what I tried

Started car and let it idle for a while.

The engine compartment fan turns on

Check for radiator fan - NOT on - Temp gauge between 8 and 0 of 180

Wait a bit more - no change.

Turn on AC, the radiator fans turns on on low

turn off AC, the radiator fan continue to run on low

After 5 minute, the radiator fan changes speed to high.

Based on my reading the radiator fan turns on low at certain temp, once the temp cross threshold, fan turns on high speed and I could not find any details on do they turn on before the engine compartment blower fan or the blower fan turns on first.

The water pump was changed approx. 4 years ago (year before I bought the car as maintenance item, no coolant leak based on the maintenance records). However, I don't see any evidence of thermostat change.

Question:1. What should start first, the radiator fan or engine blower fan

2. Seems like once I started AC which kicked off radiator fans, they continue to run even after I turned off AC. So, is there a malfunction somewhere which is not turning radiator fan on (thermostat or something else).

Any help would be greatly appreciated.

Jay

4 different events - radiator fans (would have to pull tech manual to check engine compartment conditions - not handy)

car running, temp not hot - no fan
car running, temp hot - low fan
car running A/C on - low fan
car running, A/C on Temp hot - high speed fan

The engine compartment fan is triggered by the engine compartment temp sensor, not coolant (engine) temp.