A/C components

[Boddney]

Hi all, I have a 2 GS300 with a strange sound coming from the A/C.

When it’s on and you come to a stop the engine sounds like it’s on a fast idle. But it’s not. My first    thought was the belt driven compressor but then noise doesn’t change pitch when you rev or pull away. It goes away immediately if you switch off the A/C.

Is there another component such as a pump or something that would make that kind of noise that just stays constant?

Thanks

Bod

[Herbie]

Aircon condenser fan?

[Boddney]

Is that the same fan as the engine cooling fan?

[Farqui]

James, the short answer is 'no'.

Vehicles typically have 2 cooling fans dedicated to different duties mounted behind (or in front) the radiators at the front of the engine bay.

One fan is triggered by the engine temperature and the other is controlled by the AC.

The AC fan assists with pulling air through the condensing radiator and it will also pull additional cooling air through the engine radiator.

Similarly the engine fan will primarily pull air through the engine coolant radiator but will also pull air through the AC radiator.

These big fans share duties to some extent as they are positioned behind a radiator sandwich of engine radiator, AC condenser and in some cases also an engine oil cooler and maybe even a gearbox radiator.

If the AC is off then one of the radiator fans will not operate.

These fans can often be wired by the manufacturer to keep running for a few minutes after shutting the vehicle off. So don't be alarmed if one keeps running whilst you are walking away.

[Boddney]

Wow thanks Lee that’s brilliant. I’ll investigate and get back to you soon.

Bod

[Farqui]

Crumbs, did my ramblings make sense!?!?

[Boddney]

Yay I fixed it.

You were both spot on. The O/S fan was really stiff and noisy. I took the fan off and removed the motor.

The motor comes apart really easily and it was just absolutely full of the carbon dust. I washed it out with electrical cleaner and a blow of air and it spun free. The brushes are about half worn but the armature looks to be very tired.

There was a secondary issue in that the rear brass bush/bearing was very worn at the bottom. This must be because the fans just spin on tickover whilst the A/C is on and so the bush doesn’t wear evenly. That’s my theory anyway. I turned the bush 180* in it’s housing and blobbed a bit of silicone grease in to it.

It now runs beautifully and puts the N/S fan to shame. I’ll do that one another day.

Thanks Guys, 

Best forum ever.

Bod

[Farqui]

Excellent news, well done [emoji106]