Only one of my radiator fans switches on when the car gets to 90 degrees. The other is not broken, it functions when i connect it up directly but all that 1/2 speed and full speed stuff aint working on my car. oh yes, its an ac car btw.
I have a have a good search around under the bonnet and under the dash and cannot locate the relays! I guess something is wrong somewhere and after reading all the threads on here I think unless I can locate the issue with the electrical system the best thing to do is splice in a manual override to fire up both fans at will.
has anyone else experienced this issue? any tips to help resolve this problem or indeed the location of the relays so I can set up a switching circuit for the relays would be very welcome.
Thats what I always thought. But reading the manual there is an additional section for the AC in an exige, it specifically explains how the fans are linked together. 1/2 speed for normal water cooling at 102deg, full speed when temps get over 108deg and full speed for ac, all swithcing off over 24 mph to avoid burning the motors out.
at least for the water cycle my car operates one fan only at full speed.
The ac is not charged and therefore does not work at the moment to see if the other one comes on with the ac.
Manual overide it is then - good idea in any case . That’s what I’ve done with mine, & I use the aircon button to switch the fans on.(Aircon removed when Honda’d).
There is another anonymous black box that contains some relays down on the other side of the front compartment. I used to have aircon and we junked it after some post-Honda probs and now both fans come on at full speed either from the thermostat or from manual overide.
This is the original wiring for the AC Fan control box.
So fans run in series for half speed operation - ECU earths the half speed control ( Blue/yellow wire) . The for Full speed either the ECU earths full speed control OR the rad control switch earths. ( Blue/Slate wire)
This is why only one fan has a direct earth connection, the other one in normal setting is earthed via the first, in effect giving only 6v to each motor.
To add in an override you want to find the blue/Slate coloured wire coming from the box and splice a new wire on that to earth via a switch. This will switch both fans on full speed. You may want to have a switch with an indicator so you know its on …
Thsi is the simplist solution and easy to test ! !
This is my diagram, however its for the Honda and I dont have the rad switch anymore … also this is an old diagram as the CC conversion only uses one fan !!
Maybe its just easier to find that blue/slate wire at the control box and run a switch
thanks for that information andy, i shall locate said wire and see if both fans are switching on. i wonder if the one fan operating issue is solved with the additional switch.
[quote=AndyD]Does the one fan come on full speed ?
If it does it sounds like the full speed relay is faulty … [/quote]
i have tested the two trigger wires you suggested. The blue/yellow wire when earthed switched both fans on at slow speed. The Blue/Slate one only switched on one fan at full speed.
I have opened the relay control box up and then checked the function of each relay. all work and do their job correctly.
i think the problem lies with the low speed input from the ecu. my car never has both fans on at low speed with is triggered by the blue/yellow wire. at high water temps only one fan comes on at high speed. the slower speed fan operation does not occur at all before this happens, as it should before both fans switch to high if the temp continues to rise.
also after studying the wiring diagram it appears for both fans to come on full speed requires both low speed and high speed inputs from the ecu.
all signs point to relay unit ok, and the ecu low speed output not functioning correctly. that is a tricky one to check…
at least now i have made a high and low speed manual overide switch. earthing blueyellow is low speed, and then adding the blue/slate bumps the fans onto high speed.
The ECU earths the circuit - so you need to have a 12v tester ( probe with bulb) and connect from a good 12v source to the blue / yellow wire and see if it will switch on the lamp.
Could be your ECU water temp sender ( brown one ) is goosed - although you would have other symtoms I guess …
i am sure the brown sensor is the only sensor that feeds water temp info to the ecu.
on my car the one fan comes on at around 90 degrees (at full speed.) this indicates the sensor is working. ish. although the temp at which my one fan comes on, around 90 deg’s, does not match the 108 deg stated in the workshop manual for full speed activation.
the ecu should react the level of resistance over the brown sensor to trigger the half speed ecu pin earthing at one temperature(102 degrees in the book manual), and then if temperatures continue to rise up(to 108deg’s), the drop in resistance will then tell the ecu to trigger the full speed earthing. therefore both the ecu outputs will be earthing, which fits to the circuit diagram showing a requirement for both ecu earths to be active for both fans to work full speed.
something is not right. there are tell tale bits of insulation tape around various wires going into the big plug on the fan control module and at the corresponding end at the fan plugs. it seems i might not be the first person investigating this little anomily…
i am tempted to set up two testers as you suggested directly onto the ecu output pins. but heating up the sensor in a controlled way to see if and when the switching happens will be a bit tricky…
from the exige circuit diagram, located between the fan control module and the ecu , what is this rad control switch?
I beleive the rad control switch is linked with the AC and switches on both fans with the AC refrigiant needs cooling - regardless of any ECU input.
But your problem is very strange … if only one fan works at full speed … then it really suggests that the low speed realy is not being switched - if you look at the diagram it would just be fan 2 that would be at full speed …
Does it make any difference if your AC button is in or out ( with fan on 1 ) ?
but i don’t see how just the rad control switch can switch on more than cooling fan 2 at full speed.
or does the ECU receive further information via the AC request relay which in turn allows the ECU to earth the half speed relay simultaniously…
My AC system is not pressurised at the moment, so i cannot switch it on. but this would be interesting to see what happens and see which fans would switch on at which speed!
very interesting, by the chararacter of my system i would says it is an elise system. One fan for the water and the other for the AC. but i am sure my car is an exige, what with that fine wing and a roof mounted antenna…
. That’s what I’ve done with mine, & I use the aircon button to switch the fans on.(Aircon removed when Honda’d).