1990 Volvo 740 radiator cooling fan mysteries

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Old 09-14-2020, 01:30 PM
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Default 1990 Volvo 740 radiator cooling fan mysteries

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Last edited by User 122820; 12-28-2020 at 03:44 AM.
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Old 09-14-2020, 04:26 PM
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Originally Posted by B230
I have still not had the fan turn on at all. The temp gauge is reading 12 o’clock as it should.
The engine has not gotten hot enough yet - those come on at about 225 degrees. Put a piece of cardboard in front of the radiator (temporarily) to force the engine hotter - if the fan motor, switch, relay and fuse are good - it will come on about 220-230 degrees.
 
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Old 09-14-2020, 04:51 PM
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Originally Posted by hoonk
those come on at about 225 degrees.
Use a zip tie tied through the radiator and a new grommet to keep the fan switches from popping out - A healthy cooling system with proper mixture and good cap raises the boiling point up to about 250 degrees.
 
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Old 09-14-2020, 09:26 PM
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Originally Posted by B230
the page says that the fan should run at half speed & full speed before pulsing injectors,
If you have a thermal switch in the radiator with two wires (on or off is all that switch does), a black relay, and an electric fan motor - there is only one speed - and there is not a controller to limit the speed to low or high - there are plenty of later Volvos that do that.

Later 940s use a temp sender in the cylinder head to control the fan - perhaps Mr.Chilton is referring to that. Those 940s do not have a belt driven fan (use the same water pump and pulley, w/ no fan attached) - just an electric one behind that radiator (rather than in front)
 
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Old 09-14-2020, 09:39 PM
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1991 Turbo, with mechanical fan and 1-speed electric fan that only runs with the air conditioner...


1992 turbo with no mechanical fan, and 2-speed electric fan... these have a larger radiator, too.
 
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