fan not coming on very much

[monkeydave]

my fan used to come on everythime the a/c came on and now it doesnt. maybe every 6 or 7 cycles the fan spins once, even after a long drive and the car ticking over with the expansion tank at max so nice and hot engine

it was 8c outside temp though so that might be it, and the fan does come on every now and again so it must not need to cool in these temps

it didnt even do the big spin for engine cooling when you leave it ticking over for a bit after a good run, but it must not need to cool in 8c temps

at least the fan does come on (which was my main concern) so not broken or fuse blown

it must just come on when it needs it in colder temps

anyone else experience this sort of thing?

cheers

[Downsizer]

In mine you can’t switch the A/C on unless the fan is switched to at least speed 1, so it’s running all the time.  I never drive without the fan on to provide ventilation.

[monkeydave]

i mean the fan in the engine bay on the radiator

the a/c is on and cycles ok

[jazzaro]

my fan used to come on everythime the a/c came on and now it doesnt. maybe every 6 or 7 cycles the fan spins once, even after a long drive and the car ticking over with the expansion tank at max so nice and hot engine

it was 8c outside temp though so that might be it, and the fan does come on every now and again so it must not need to cool in these temps

it didnt even do the big spin for engine cooling when you leave it ticking over for a bit after a good run, but it must not need to cool in 8c temps

at least the fan does come on (which was my main concern) so not broken or fuse blown

it must just come on when it needs it in colder temps

anyone else experience this sort of thing?

cheers

Fan (outside fan you mean?) comes on only if the A/C coolant temperature exceed a preset value: in winter fan could be not necessary in  every cycle.

[monkeydave]

yeah the one on the radiator

thanks, prob just the colder weather, just strange after a 30 mile run and hot engine

[jazzaro]

yeah the one on the radiator

thanks, prob just the colder weather, just strange after a 30 mile run and hot engine

Normal conditions.
Engine coolant does not affect the A/C coolant, so engine can be hot or cold with no consequences for the A/C circuit.
As said, the A/C ECU checks the fluid temperature (or the pressure) after the A/C radiator and then, if the compressor is on, will switch the fan on or off.
In winter the external temperature can be enough to cool down the fluid without the fan running.

[ColinS]

Interesting.  I always thought it was the engine temperature sensor which measured the engine coolant temperature and passed the information back to the ECU which in turn commanded the radiator fan.  Nothing to do with the A/C.

[jazzaro]

Interesting.  I always thought it was the engine temperature sensor which measured the engine coolant temperature and passed the information back to the ECU which in turn commanded the radiator fan.  Nothing to do with the A/C.

In old cars A/C system and engine managemente were completely separate, and there were two external fans: one for engine cooling, another for A/C cooling.
In recent cars (last 20 years, I mean), often with A/C standard fitted, they use a single fan operated by the engine ECU: this because this ECU follows the fan and idle management, both influenced by the A/C compressor. So now the external fan can run both for engine cooling (cooling fluid too hot and/or vehicle speed too low), or  for A/C (a/c fluid too hot and/or vehicle speed too low). Heat exchangers and circuits are separate, but there is a single ECU.

[Jocko]

Interesting.  I always thought it was the engine temperature sensor which measured the engine coolant temperature and passed the information back to the ECU which in turn commanded the radiator fan.  Nothing to do with the A/C.

That is how my Mk 1 Jazz operates (no A/C), but in the time I have had the car the radiator fan has never come on because circumstances have never allowed the coolant temperature to reach the switch on point. Only once reached 93 C.

[monkeydave]

in the summertime every time the a/c compressor cycled the fan came on and now the outside temps are lower the fan comes on every 6 to 7 cycles

it was ticking over for ages and usually in the summer that would cause the fan to come on for a long time to cool the engine as well but it must not have needed the fan in the colder weather

im happy that my fan actually comes on when the car wants it on and is not broken