FAQ
TL;DR: On a 1999 Astra G, the radiator fan is controlled by a front-mounted module, and above 60 km/h airflow outperforms the fan. "Above 60 km/h the fan makes little sense." [Elektroda, ociz, post #16694438]
Why it matters: Helps Astra G owners quickly locate the right component and fix overheating without chasing the wrong green relay.
Quick Facts
- Fan control: dedicated module mounted under the left side of the front bumper. [Elektroda, Anonymous, post #16692627]
- Cooling setup: two-speed radiator fan; ECU-managed via the module. [Elektroda, Anonymous, post #16693867]
- Fuse vs relay: the engine-bay fuse exists; the relay you seek is not in that fuse box. [Elektroda, pusty20, post #16693336]
- Highway rule of thumb: above 60 km/h, airflow renders the fan largely unnecessary. [Elektroda, ociz, post #16694438]
- Quick test: unplug the coolant temp sensor; the fan should switch on in failsafe. [Elektroda, Mateusz03041994, post #16694193]
Where is the radiator fan relay on a 1999 Opel Astra G?
There isn’t a conventional fan relay in the engine-bay box to swap. Cooling is handled by a fan control module mounted under the left side of the front bumper. Access it from the wheel-arch or undertray area. [Elektroda, Anonymous, post #16692627]
Is the green relay in the engine bay the radiator fan relay?
No. A user suggested the green relay, but a moderator corrected the claim as not true. The fan is managed by the external module, not that green relay. [Elektroda, Pedros050, post #16692295]
Does an Astra G without A/C still use a cooling module?
Community experience indicates Astra G models used a two-speed fan with a control module, even on lower-output engines. “They all had a two-speed fan” is the prevailing view. Verify by checking under the left bumper for the module. [Elektroda, Anonymous, post #16693867]
Why does my Astra G overheat at higher speeds if the fan works?
At speed, ram air should cool better than the fan. Overheating suggests restricted airflow or heat transfer. Check radiator fins for dirt and insects, and compare coolant vs radiator temperatures with a thermometer, not just the dash gauge. [Elektroda, Strumien swiadomosci swia, post #16694253]
How can I quickly test if the fan failsafe works?
Unplug the coolant temperature sensor with the ignition on. The ECU should trigger the fan as a safety measure. If it does, wiring and fan power likely exist; investigate sensor data or the module next. [Elektroda, Mateusz03041994, post #16694193]
Where is the fuse for the radiator fan on Astra G?
The relevant fuse is in the engine-compartment fuse box. However, the fan’s switching is handled by the bumper-mounted module, not a simple relay inside that box. [Elektroda, pusty20, post #16693336]
What should I check first when diagnosing fan-related overheating?
- Measure actual coolant and radiator surface temperatures with a thermometer.
- Inspect the radiator face for debris and bent fins.
- Confirm if you have one or two fans and whether A/C is fitted. [Elektroda, Strumien swiadomosci swia, post #16694253]
How do I access the fan control module under the bumper? (3-step)
- Turn the steering left and remove left wheel-arch liner clips.
- Peel back the liner; look near the radiator’s left lower area.
- Inspect the module connector for corrosion, damage, or loose pins. [Elektroda, Anonymous, post #16692627]
My fan stops when I remove the key—normal?
Yes. On Astra G, the fan typically loses power with the ignition off. If overheating persists, focus on airflow restrictions, thermostat operation, or the control module’s performance while driving. [Elektroda, Mateusz03041994, post #16694193]
Does highway speed reduce the need for the radiator fan?
Yes. Above about 60 km/h, airflow through the radiator generally exceeds what the fan can provide, so the fan may not engage. This is normal behavior. [Elektroda, ociz, post #16694438]
What’s the typical fan speed setup on Astra G?
Astra G commonly uses a two-speed radiator fan controlled by the external module. Low and high speeds let the ECU match cooling to load, reducing noise and electrical draw. [Elektroda, Anonymous, post #16693867]
Autodata shows a module—should I trust it here?
Owners have confirmed that Autodata indicates a fan control module on Astra G, matching the bumper-left location reported by users. Use it to cross-check wiring colors and pinouts before testing. [Elektroda, Mateusz03041994, post #16693804]
I see a dashboard light linked with the fan—what does that suggest?
Some owners report a canister/fan-related lamp appearing with intermittent fan behavior. Treat it as a prompt to inspect the module, wiring, and connectors for faults or moisture ingress. [Elektroda, Anonymous, post #16693867]
What information should I provide when asking for help?
State engine code, whether you have A/C, and the number of fans. This determines wiring, control strategy, and component locations, speeding up accurate diagnosis. [Elektroda, milejow, post #16692277]
