Thermostat

[shy7g]

[quote="henrym3"]
Am suffering considerable confusion with the mod. Had a small leak from one of the pipes which needed the fan and cowl removed to get at. Leak fixed, topped up and decided to run engine without fan fitted to see if the aux/ac fan would cut in. It cut in at 90c and kept the temp at 89/90c for 20 mins. Only runs foe 30 sec at a time. Yet on my test run yesterday I saw idling temps of up to 99c with both fans fitted. My main reason for wanting to get my head round this is I want to fit an electric fan but need to decide what temperature I want it to cut in. To low and it will run unessarily
[/quote]
the best of luck, but you don't need to be told the old saying, you know the one that starts - "if it's not broke  **** *** **", there should be a voice in your head telling you "NO", after all if it's designed to do it........ , but still will be interested in your pursuit...

[henrym3]

There are no voices in my head saying " NO "I fully believe this is a very good mod. The difference in under bonnet temperatures is quite noticeable, yesterday was a day of excessive speed, acceleration and prolonged idling. Today was back to normal everyday driving and the vehicle runs a good 10/15c below previous. Certainly no running issues. When I get round to getting the emissions done I'll post.
A Question. The a/c fan which runs via a PWM, is the motor in the fan different or would it run with just a 12v supply. 

[Horizon]

The AC fan is quite complex in the way it runs, it's not a simple 12 V supply, and very difficult to test / fault find on
If your going down the electric fan route, get an aftermarket set up working on a temp switch on the radiator, like the 1980's Ford Fiesta's.
I'd stick to standard myself

[henrym3]

I appreciate that the PWM is quite complex and difficult to test but that isn't what I asked. As for staying standard that isn't going to happen.

[X5Sport]

You would have to remove the electronics from the fan motor itself in order to give you direct control.

[henrym3]

Thank you for that, so that eliminates my thought process of finding a fan on an scrappy BMW. Although correct me if I'm wrong but the PW Module gets it's 12v from the ECU and converts it to PW and feeds that information to the fan. So if I could get the whole system and replace the 12v from the ECU with 12v from an temperature sensor? Would this not work.

[X5Sport]

Assuming the sensor is just a switch in reality, then connecting a 12V feed to it should be fine.  It was how it used to be done when we still had 'simple' cars!  The fan was either on or off.

You will need to check the power ratings of the sensor though.  BMWs electric fans are 600W (50A), or higher if the car has a tow bar, so you may need the sensor to drive a relay that switches the fan power.  It will only be a simple make/break relay.  The fan needs to be that powerful to push enough air through.

[henrym3]

Excellent info, thanks

[X5-D-Sport]

Hi Henry,

Re AC fan on the front of the engine....
I've had no joy in getting mine to work in 2 years, & decided to get an 80 Watt after market fan.
The original AC fan motor is a bit of a monster & hugely powerful... & is actually only any use when the vehicle is stationary in HOT sizzling traffic - when you need it the most...
So...

I had an idea..
I have a spare motor unit to diddle with, & that I have worked out how to remove from the original fan motor from the vehicle without removing the entire front of the vehicle in about 20 minutes easilly...

Then I intent to remove the 3phase DC motor guts of the original complicated fan unit, make an adapter & retro fit the standard Brushed motor from an After-Market fan into the original mountings & use the original fan...

Obviously it wont be as powerful as the OEM unit, but experiments with the budget fan have proved that it is enough to freeze your privates of with the vehicle stationary.

As I have a mini-lathe, the adapter to use the OEM fan with an cheap aftermarket motor is simple to make.
I will post the images when completed properly... and happy to supply the adapters for £25 each (UK) if any one wants them - (just about covers Aluminium & postage).
Regards
Grant B

[henrym3]

An interesting post from my point of view. My a/c fan is working fine, its the viscous fan I want to replace. To that end I went to the scrappy today and bought a pwm fan (puller) of another BMW, with shroud which will fit my radiator. Like mine it has 3 wires. THICK  Brown, THICK Red/Blue. THIN Black/green. Need to figure out how to get it to work. Failing that I'll be going down a similar route and will need to pick your brains. BTW the scrappy fan was £15
Just to note I did over 200 miles today and I am impressed with the lower running temperature, If your moving no matter how slow or fast you never see plus of 93c. So my aim will be to try and get the electric fan to cut in around 97c which means it will only ever need to work after prolonged idling.

[X5-D-Sport]

Re 97' activation...

im pretty sure accurate thermo switches are available from Maplin/Ebay that could be easilly mounted to the top of the rad & a 30 amp 12v relay & aftermarket cooling fan will work perfectly..
20mph forward movement will keep an engine cool in most situations... as you say.. traffic jams & idling is the time you need the engine cooling fan to run.

personally, i like my the viscous unit due to its reliability & simplicity for engine cooling.. but I may be converted one day im sure....

[henrym3]

To dig this up again, I have fitted a fan from an E46 318i with shroud, doesn't cover the complete rad but does a goodly part of it. Didn't pursue the PWM route just using it as a normal fan. Cut the top hose just beyond the outlet from the coolant pump, so near to where the DME gets it's temp' reading from. Inserted an alloy piece which allows a BMW temperature sender switch to be screwed in.  Fitted a double switch 93 and 99 degrees on 88 or 93 off, simply used this switch because I had one in my box of bits. Wired it using the 99 on 93 off part of the switch and used the switch as the ground for switching the fan on. Bought a Cheap relay which incorporated a 30 amp fuse, wired it up and blew the fuse and again and again, at this stage even I realised this was not part of the master plan. An old saying in my kept popping up, "buy cheap, buy twice" so borrowed a BMW 4 pin relay, put  30 amp fuse in line with fan. Works fine, BUT randomly the electric A/C fan comes on, a/c not switched on. I have put this down to heat soak from radiator to the condenser?? Takes for ever to now to get to 99 degrees and when the fan kicks in it very quickly brings the temp down to 93 degrees. As X5 D Sport said, on the road it just never gets anywhere near the fan coming on. So it's on trial now for a month or so, got to be 100% reliable or it's binned and back to the viscous.