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Read you rpost from further down the board. 700 1990

posted by  tonkyman on  Wed Aug 3 03:00 CST 2005
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I just read your post from further down the board.

I'm not trying to be a smart axx I just want to help you understand how it works so you can decide how best to proceed.

The 740 has a pusher fan that is controled by a relay. The relay is triggered in two different ways. There is a thermal switch on the radiator (pass side top) and there is a high pressure switch in the A/C system. If the air is on and the head pressure gets to high the pressure switch grounds the relay turning the aux fan on. When the pressure comes down the fan turns off. In the event the engine temp raises to a point the radiator mounted thermal switch closes and it grounds the relay and turns the fan on. The relay on my car was bad due to bad solder joints but was easily fixed.

I know of serveral people that add an extra switch to ground the relay and turn the fan on when they want, like in heavy stop and go traffic. It seems a bit pointless to me but they claim it works to bring the temp down and make the air work a little bit better.

If you just want better A/C preformance at idle and low speed you may want to read the 740/940 FAQ. The A/C section has a link to a VOV that works wonders for increasing A/C preformance. http://www.brickboard.com/FAQ/700-900/HeatingAirConditioning.htm#VariableOrificeValveAddition

I have not used it on a Volvo but it works great on GM cars.

I hope this helped.

Tony T
--
Tony Turner 89 Volvo 240DL 257K, 1980 Mercedes 240D 360K, 1982 Mercedes 300D Turbo Diesel 153K (R.I.P.), 2 1992 Geo Metro Convertables (I'm not sure why??)






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