850 electric fan in 240



  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    I'm going to use this thermostat to switch high speed

  • A_Volvo_DriverScott (@A_Volvo_Driver) Victoria, The Revenue State
    I'm just going to get one of you guys to sort this out for me. It might as well be magic.
  • DCW242Duncan (@DCW242) - Western Victoria
    edited February 2016
    Thanks guys!

    @jamesinc - I later fitted a set of washer to my fan shroud bolts, after I fitted the bolts they did cut into the shroud a bit.

    240 (@240) wrote: »
    OK then.
    How does one wire up the fan?

    That part is fairly easy, there's some wiring diagrams on a few Volvo sites. Dave Barton has a few of them on his website. basically you will need a relay, some kind of temp switch, the fan, and some fairly basic wiring. there's a few ways to do it, and it depends on what kind of relay and switch you use. basically you will need to power the relay via a fuse, power the fan from the relay, and switch the relay using the temp switch.

    At the moment I have an 87° switch in the lower hose, and two Bosch relays. one for each speed. with the higher speed connected to the temp switch, and the lower speed connected to the aircon. that seems to work pretty well, but once the fan has ran for a bit and switched off again, the temp gauge is pretty low. so I might have to get a temp switch that switches off at a higher temp.

    I'll take some better pics of my set up and update the post.

  • A couple of old diagrams here that I drew up 10+ years ago when playing with electric fans on my 242:



    In both of the elec fan conversions I've done I added a switch on the dash to allow manual control of the fan, if the temp switch ever failed. I've never needed to use the feature, but it's nice to know it's there. In the 242 I added an indicator LED too, for no good reason.

    For what it's worth, this is the aftermarket fan I've had on my 760 Turbo for the last 8 or so years:


    As you can see there's no shroud, and no air gets drawn through the corners of the core by the fan, but I've never had any overheating issues with the car, even in traffic in 40 degree heat etc.

    The point I'm trying to make is, don't worry too much about perfecting airflow through shrouds, they're not as essential as you might think.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    edited June 2017
    Here is my contribution. I'll edit this post as I go.

    Electrical configuration
    You will need:
    • 1 x 38mm sender adapter, with 1/8 NPT fitting
    • 1 x 1/8 NPT thermoswitch with 82C (180F) on and 73C (165F) off
    • 1 x the relay block from a P80 Volvo (850 or early x70 models)
    • Assorted wires. Make sure your primary power and earth wires are as thick as the wires coming out of the fan, or the current will melt them.
    • (OPTIONAL) 1 x toggle switch or, if you can find one, unlabelled Volvo 240 accessory switch for that OE feel - this switch, if installed, can be used to bypass the thermoswitch and force the fan to run

    What I used (may be out of date):

    Opinion: don't waste your time with a second-hand thermoswitch. This is a critical component in your engine, and it is important that you can be confident that it will work reliably and consistently. Most of the complaints I have read of e-fan conversions have been related to thermoswitch failure. Do not skimp on the thermoswitch. A new one, as you can see, is a paltry US$25.
  • A_Volvo_DriverScott (@A_Volvo_Driver) Victoria, The Revenue State
    Good tip on the OE switch idea. I still have a green Fog Light switch which I could use.
  • @jamesinc did you put the thermoswitch in the radiator, block or head?
  • I've got an electric setup in my 740 and I'm wondering if the thermoswitch (new of course) for a 940 would be suitable.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    @240 I haven't fit it yet, but I will put it in the lower rad hose.
  • sorry guys ive been trying to post this via iOS for the past week. havent been on the MAC.

    More than happy to do it all for you Scott.
    That's if you can deal with me for the day ;P

    On the specific fan subject. Any of the "generic" fans will do the job also. Especially if you combine a push with the traditional pull.

    james as ive mentioned to a number of people doing this retro fit. including duncan, i advise against the instillation of of the thermo sensor in the lower rad hose (cold side) of the radiator.
    this causes the fans to work inefficiently. on/off very quickly/frequently. it doesnt allow enough cooling capacity. the wiring and relays will cop some abuse because of this. top rad hose or in the head is the ideal spot. as the thermo switches are sensing where the hottest part of the coolant is.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Okay so my logic is as follows. The thermostat in the head ensures coolant leaves the engine once it gets to 87 degrees. The radiator and fan apply best effort cooling. The only part of the system that is unmeasured is the temperature of coolant entering the engine. So my goal is to measure coolant temp entering the engine and make fan switching decisions based on that.
  • The issue is monitoring v's actually cooling.
    You want the fan sensor to sense when it's too hot and cool appropriately. Not sense when it's too hot and cool after its WAY too hot.

    Ultimately if you have you fan sensor set to 70-80deg in the lower rad hose, your coolant temp might actually be 100+ deg at which case when the ambient temp is 30-40+ deg it's seriously sketchy.

    think like this, my fans monitor the temp (with a digital gauge) after the fans switch off at 84deg, on the hot side, come the time its passed the radiator and cycles it can get as low as 77deg before it starts climbing again.

    monitoring the temp after its been cooled isnt really much of a worry. its imperritive to cool when its at its hottest. not coolest. otherwise the temp can spike between the thermostat and cold side of the radiator. and potential for bang.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Is there really much of a potential for that though? Because round trip from the thermostat to the water pump would be what like 10 seconds at most?

    @blondejay, at the upper hose, what temps does your fan switch on/off at?
  • It's on at 85deg off at 84deg, with today's ambient temp at Driveway level 33deg and no airflow. (note i use an 83deg theromstat)

    The sensor drops to 82deg before climbing to 85deg again, with about 3-5mins inbetween, at idle.

    back when i first installed this thermo setup. i had the sensor in the lower (cold hose) the fan would switch on at 85deg off at 84deg and in a matter of 10sec or so it would come back on again. at idle. fans had to work significantly harder/more frequently to maintain a safe operating temp.

    when it was setup like this i had two fuses fail, (melted) in turn the fans didnt work and i boiled.
    this was in heavy traffic on a 36deg day.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    I have a different thermoswitch to you. My thermostat is an 87 degree thermostat, and the thermoswitch is on at 88 and off at 79. I'm going to run it in the lower hose because I still think this is where the most useful measurements come from. Coolant in the upper hose is always going to either be not moving at all, or it's going to be 87+ degrees, so measuring if it's 88 degrees is kind of useless - I know it is going to be at least that temperature.

    I think the significance of there being a latency between too-hot coolant leaving the engine and getting to the thermostat, and thus the cooling system being too slow to react and an overheat occurring, is overstated.

    The radiator is best-effort. It doesn't guarantee it will do anything, it just maximises potential for heat dissipation. Because of that, in my opinion it is important to make decisions based on the radiator's output.

    In any case, I'll have a (labelled) temp gauge in the cabin initially to see what temps are like in the head.
  • Well thermostat isn't a concern for the fan sensor.

    Basically the fans will be working much more frequently.
    Even on the mounting guide for Davis Craig, all their guides are to install the sensor in the top radiator hose or insert into the hot side of the radiator fins.
    And I'm sure it will find that it's the case with many factory fitted sensors in even modern cars. I highly doubt they are reading the cold side of the coolant system. :/

    Funny enough though, on the hot days here in melb, 35+ hitting the freeway sometimes with minimal traffic, I've seen my Led (trigger light, connected to the pull fan) light up for almost the entire 40min drive. This tells me that during high ambient temp low rpm, high air flow driving conditions that the coolant temp can not get below my fan sensor set temp of 85deg.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Volvo put their thermostat on the cold side on models with e-fans from factory. I just don't think measuring the hot side is as useful. And the fan switching on/off all the time would be just as much to do with the thermoswitch on/off temps.

    The only time I want to run the fan is if the coolant exiting the radiator is too hot. If I put the switch before the radiator, then the overheated coolant leaves the radiator and goes back through the engine a second time before getting to a point where a measurement is taken and the fan is switched on. If you put the switch on the outlet side of the radiator, you can switch the fan on as quickly as possible and minimise the temperature spike.

    Anyway, ultimately, I think it's just a difference of opinion. I'm going to run the sensor on the lower rad hose because it makes sense to me to do it that way, and because I've selected a thermoswitch based around a lower hose application, rather than an upper hose application, which would want a thermoswitch with a hotter 'on' temperature.
  • blondejay wrote: »
    Funny enough though, on the hot days here in melb, 35+ hitting the freeway sometimes with minimal traffic, I've seen my Led (trigger light, connected to the pull fan) light up for almost the entire 40min drive. This tells me that during high ambient temp low rpm, high air flow driving conditions that the coolant temp can not get below my fan sensor set temp of 85deg.

    At freeway speeds the fans windmill and generate power, so if you have your indicator LED wired to the same pole of a SPST relay as the fan motor, the LED will light as a result of that current flowing.

    To avoid this, I used a DPST relay with the motor wired to one pole, and the light (I was using a bulb) to the other, this way they were electrically separated when the relay was open. Using a bulb, I could watch it begin to glow faintly at about 70km/h, and get pretty bright at freeway speeds!

    I've never seen any of my electric fans come on above 40km/h, even in very high ambient temps.

    Upper or lower hose sensing methods both work well, as long as the switches are suited to the location. The setup on my 760 uses a sensor in the head and an adjustable controller, and holds the gauge needle rock solid under all conditions, and doesn't cause the fan to run for very long or too frequently at idle.

    Note that virtually all OEM applications use sensors in the head or thermostat housing.
  • Great info in this thread. Is there much less noise with the e-fan? Lose that noticeable 240 fan humming
  • Vee_QueVee_Que (@Vee_Que) South Eastern suburbs Melbourne.
    Turbos and 3" exhausts overpower clutch fan noise. ;)

    Stock 940 e fan senses off the head or the hot side of the radiator, as does the c70... Fwiw. And I pushed jay to put it on the hot side because of the cycling excessively.
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