Skip the auto shop - Our mechanics make house calls

Q: the high speed of coolant fan doesn't turn on when the engine overheats

asked by on

its the opel astra G CD 2004 the car is a Brazilian made for Chevrolet (in Brazil called Chevrolet astra) but came to Egypt under the Opel name from the GM factory in Brazil with z16xe engine and an auto transmission with HSFI 2.1 ecu, it originally has an HSFI 2.3 ecu that came with the car from the factory, but it showed malfunctions and had to be replaced and HSFI 2.3 wasn't available later the ecu dropped signal to the fuel pump relay and the car wasnt able to start, the local mechanic repaired it by getting a separate 12v signal only when the ignition is on through a diode from a near by relay and the car was pumped back to life (this isnt the main problem but i wanted to denote a faulty ecu) now the ecu dropped signal of the high speed radiator fan so it would turn on but only on the low speed thus on daily use there is no overheating unless I open the A/C in traffic jams while on the highway it cools back can I check for wiring error at the relay box or change wiring or what?

My car has 7427871 miles.
My car has an automatic transmission.

Hi there. The high speed cooling fan is usually controlled by a spectate thermal switch, so it’s possible that this thermal switch has failed. However, you should try as hard you can to obtain the correct ECU for this car, as that can only improve the situation. If you need help with this have a local expert diagnose the AC system to assist with proper repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • the high speed of coolant fan doesn't turn on when the engine overheats

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Truck starts to overheat and blows cool from the heater but fixes itself after hitting a bump.

The overheating may also be caused by other issues such as a bad heater core. This is a small radiator used to warm up the interior of the vehicle making the heater operational. A valve controls the flow of hot...

Q: Electric Cooling Fan Remains On Even When Car is turned off

The radiator fan will be controlled by the engine ECU (electronic control unit) through a relay. The relay is most likely your problem. When the fan shuts off, it can cause a small arc on the relay points that will...

Q: Pin in ECU connection broke and car won't start

This sounds like a pretty big deal. If the pin is one the connector side, you may be able to simply replace it with a new pig tail end. If the broken pin is in the ECU, unfortunately the ECU...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...