Cooling Fan

[Guest Jonnyround2003]

I have a ford dohc engine the fan comes on all the time after a while of running is this normal to come on to keep the engine cool and can anyone send me a diorama on how to connect the fan to the ignition so when I turn the car off the fan turns off. At the moment it just runs and won't turn off and drains the battery

[kevin the chicken]

It shouldn't come on all the time if you are moving and even then it should shut off once it has cooled enough. I presume there is no sign of overheating on the temperature gauge. It may be that the switch or sensor has failed, I had to put a new one on my car. I will leave the wiring instruction to somebody else as everything on my car is wired through a kill switch so key out means no Electrics!

[Guest 2b cruising]

The electrical circuit is quite a complicated thing. Especially for people like myself that don't like the black magic side of things.

I do know there are two switches on the cooling system. One for gauge and the other for fan.

The fan is controlled by the larger of the switches and is in the Bakelite thermostat housing.

There are also two relays in the main fuse box, one for low speed and one for high speed.

These are controlled through the engine ecu.

Can't te you which two relays but I do know they are next to each other.

It can be one of these sticking on.

No matter how they are fed, your master switch (if fitted) should cut the power to the fans.

I hope this gives you some idea what to look for.

Ken.

 

Edit. Take great care handling the Bakelite thermostat housing. They are getting quite rare these days.

Switches are still available.

Edited July 6, 2016 by 2b cruising

[Big Jim]

Try this http://nw.rhocar.org/fan%20wiring.htm

[Guest Jonnyround2003]

I have all new coolant new pump new thermostat what about getting a higher rated temp sensor I have used a temp lazer reader and its around 90 c when moving and doesn't really drop. Thanks for the diogram will look at that I may need a bigger radiator or a new one

[Guest Jonnyround2003]

I have all new coolant new pump new thermostat what about getting a higher rated temp sensor I have used a temp lazer reader and its around 90 c when moving and doesn't really drop. Thanks for the diogram will look at that I may need a bigger radiator or a new one

[Guest Jonnyround2003]

I have all new coolant new pump new thermostat what about getting a higher rated temp sensor I have used a temp lazer reader and its around 90 c when moving and doesn't really drop. Thanks for the diogram will look at that I may need a bigger radiator or a new one

[Big Jim]

The biggest problem with our cars is cooling, you need to make sure that as much air is going through the radiator that can do, to do this blank off as much as you can around the outside of the radiator to stop air going around it, rather than through it.

The thermostat opens around a specific temp (marked on it) allowing hot water to exit from the engine into the top of the radiator, also allowing cool water from the bottom of the rad into the engine. As yet the fan should not come on.

Once this cycle has gone on over and over for some time, all the water in the rad could become just as hot as the water in the engine so the over-all water temp starts to build up. Depending on what temp the sender for the fan is (usually about 5 - 10º higher than the stat temp), this should then switch the fan on which pulls / pushes air through the radiator at speed to cool it, hopefully!

Other things that influence cooling or lack of it are, blocked radiator / pipes, bad thermostat, too small a radiator. but mostly poor air flow.

 

To stop the fans running on after switching off the ignition, you'll need to check the wiring to the relays, ideally the feed to the relay should only be through the ignition (or the ECU correctly) so that it's only live when the ignition is on. The main feed to the relay that will drive the fan is also best from a fused ignition 'on' feed. The sensor is not in the live side of the wiring, but in the 'return' or -ive side, as it switches to earth.

[Guest Tim Norman]

As an aid to cooling consider someway of getting all that hot air out from under the bonnet too!

[Guest 2b cruising]

I am still wondering how come it does not shut off after running on for a while.

If you were running to hot (90 is not to hot) then the fan would cool it quite quickly.

I am still thinking electrical/electronic fault.

If you can get away with putting a v6 32 valve highly tuned engine under sound proofed and under tray'ed golf bonnet without any venting and the exhaust wrapping around the engine, our cars should easily run without bonnet vents if all is in good order.

The main thing is clear airway to the rad and through it.

Back up pressure should not happen as we don't seal the bottom end.

Edited July 6, 2016 by 2b cruising

[Guest Jonnyround2003]

last night i disconnected all the temperature sensors to the gauge still rises i have the vicky loom with blue and green should be from tempo sensor cable and 12 volts the other side to the smiths gauge and the gauge still rises is this the correct cable ?

[Guest Jonnyround2003]

I have made more vents in the bonnet to get rid of heat my rad is 450mm wide by 380mm high 40 mm thick the rad is at a slope and not vertical stood up i could do with helping to direct air through the fan

[Guest 2b cruising]

If you can get hold of some reasonably stiff rubber matting, block any gaps around the sides, top and bottom of your rad.

If you have things such as air filter, horn or any other bits except intercooler or oil cooler restricting the air getting cleanly direct through your rad, it is best to find somewhere else to mount them.

My dohc used to run hot all the time until I cleared out the clutter.

Your rad mounted on a slope is reportedly the most efficient way to mount it.

I have also fitted an air scoop underneath in front of my red to force air from under the car up through the radiator.

I changed my air filter from the drum type to the coned type and mounted it in such a way that it blocked part of the gap between the body and the radiator.

I also fitted my horns in the same place to further restrict the escape of air along the side of the rad.

I also removed the sick and blow header tank, fitted a higher pressure radiator cap to raise the boiling temperature.

All of the above actions have cured any signs of overheating that I used to get.

Now I can drive it as hard as the law allows, in any Kind of weather with full confidence that it won't boil or overflow.

[Guest Jonnyround2003]

Thanks 2b cruising will try this did you see the post about my gauge rises with all the sensors unplugged what could cables do you have to your temp gauge

[Guest Jonnyround2003]

2b what rad did you fit ?