freemanrx7

My belt whines since I don't have a double pulley. When I start my car in the morning the fan engages for 1min or so. Is there a simple way to stop it from doing that? I'll be upgrading to a double sometime but having the fan engage for no reason is annoying.

Why does the fan engage on startup?

clokker

iTrader: (2)

No, your belt whines because it's not properly tensioned.
Presumably you're talking about the stock, thermoclutch fan, right?
It's always "engaged" in the sense that it always spins, never sits still.
The accelerated warmup adds to the impression that it's "engaged" since it will spin faster till the idle drops.
No.
You can festoon the entire engine bay with belts and it won't change how the fan behaves.

[/QUOTE]
Switch to an electric fan and this whole "issue" goes away.

freemanrx7

Thanks for the quick reply. I'll check the tension on the belt again but it seems tight. The belt only makes noise during a cold startup. It last for about 1 min then I don't here the noise again even after I start the car later in the day.


Again thanks for the quick reply

clokker

iTrader: (2)

You might be getting condensation/moisture on the pulleys as they sit overnight, which could cause a little noise at first.

arghx

iTrader: (3)

jackhild59

iTrader: (7)

When you start up cold, the thermo clutch must re-distribute the fluid into the proper working passages because it has drained to the lower part of the unit. Until this happens, the clutch will essentially be as fully locked as it can be, around 75-85% of shaft speed. This is why engines with a clutch fan 'roar' when they first start up. It is the nature of the beast.

You will read lots of statements on this forum that the clutch 'unlocks' 'disengages' etc. on the highway or at a certain speed. Horsefeathers. After the initial startup, fan speed is entirely temperature dependent. Look at the chart posted above. The clutch is designed to vary fan speed based on the temperature of the airflow through the radiator into the engine bay.

The reality is that a fan clutch can never truly unlock( or fully lock). The 'unlock' is physically limited to 25% to 35% of shaft speed. Design choices influence the degree of max and minimum lockup-there are trade-offs. In very modern cars with fan clutches, there is an additional electric clutch that can disengage the fan for improved fuel economy.

arghx

iTrader: (3)

A lot of newer cars use a duty control electric fan to throttle fan speed. The Evo X and 370Z do. You can also buy aftermarket units to do the same thing (SPAL makes one).

jackhild59

iTrader: (7)

Yes, on an electric fan. Lincoln Mark VIII did it too.

I worked on the A/C of a BMW 540 that Pulse Width Modulated the fan speed on the condenser fan relative to the refrigerant pressure in the condenser. It worked very well.

arghx

iTrader: (3)

Well the refrigerant pressure thing is no surprise. The Subarus (WRX etc) doesn't use duty control, but they use fans that operate in two speeds by the ECU switching them from a series circuit to a parallel circuit. Part of the ECU's control logic incorporates A/C pressure. There is low and high A/C load logic.