Discussion
yeah well, what can i tell you - i've spent some time on this topic!
take a feed off starter motor supply, which is directly connected to the battery, and supplement the original supply to the fans, putting in some heavy duty cable to minimise current losses. this should (in theory ) increase the amount of current available to the fans, making 'em go faster, and taking the load off the fan fuse which blows because of the switch-on current surge.
so, i will take the original connection for one fan, and use this just to switch a relay, which in turn will switch the new supply from the starter motor to the second fan. i will also replace the stadard ( on mine! ) 40 amp fan fuse for a 25, as the original circuit will now only be running 1 fan and a relay.
make sense?
>> Edited by chimburt on Saturday 19th April 11:05
take a feed off starter motor supply, which is directly connected to the battery, and supplement the original supply to the fans, putting in some heavy duty cable to minimise current losses. this should (in theory ) increase the amount of current available to the fans, making 'em go faster, and taking the load off the fan fuse which blows because of the switch-on current surge.
so, i will take the original connection for one fan, and use this just to switch a relay, which in turn will switch the new supply from the starter motor to the second fan. i will also replace the stadard ( on mine! ) 40 amp fan fuse for a 25, as the original circuit will now only be running 1 fan and a relay.
make sense?
>> Edited by chimburt on Saturday 19th April 11:05
Chimburt - interesting posts. My car has air-con, reduced sized front number plate, no splitter and I've recently had a fan override kit fitted (which includes a fans-on indicator light). In the recent warm weather I've noticed the fans come on after about 10-15 mins warm-up from a cold start and they stay on, even during prolonged periods at steady motorway speed.
As far as I can see there are two possible reasons for this - otter switch cuts out at too low a temperature or fans not running at full speed. The fans come on at an indicated 80C and don't switch off even when the temp drops to below 70C. However, I know the gauge can't be relied on to give an absolute temperature, only useful for relative changes.
I'm thinking of getting the otter switch replaced to see if it makes any difference. The fans are working very hard and may be over-cooling the engine.
As far as I can see there are two possible reasons for this - otter switch cuts out at too low a temperature or fans not running at full speed. The fans come on at an indicated 80C and don't switch off even when the temp drops to below 70C. However, I know the gauge can't be relied on to give an absolute temperature, only useful for relative changes.
I'm thinking of getting the otter switch replaced to see if it makes any difference. The fans are working very hard and may be over-cooling the engine.
The performance of the fans will be dependant on the condition they are in, the older they are (use wise, not age) the more current they draw. The more current they draw the more fuses they will blow, supplying more current to a motor in this condition is not really a cure. It is equivalent to bailing out a boat with a bigger bucket to stop it sinking, the correct option would be to fix the leak in the hull.
If your choice is to go down the more current route then the best solution would be to do away with any connection to the fusebox completely, the next problem you will have is it overheating and melting. It would be a better job to just rewire the whole thing properly under the bonnet from scratch. Taking a heavy power supply from the power connection to a starter is not good practice, a separate connection to the live battery terminal is better.
Having the fans running on after the ignition is switched off serves very little purpose and can cause other problems. Firstly if a relay sticks on, the fan keeps going until it burns out or you have a flat battery (ask Ford why they had to recall so many Sierra Cosworths). Secondly, if you have a voltage drop alarm and the fan switches off after the arming delay it will set the alarm off.
Ivan
If your choice is to go down the more current route then the best solution would be to do away with any connection to the fusebox completely, the next problem you will have is it overheating and melting. It would be a better job to just rewire the whole thing properly under the bonnet from scratch. Taking a heavy power supply from the power connection to a starter is not good practice, a separate connection to the live battery terminal is better.
Having the fans running on after the ignition is switched off serves very little purpose and can cause other problems. Firstly if a relay sticks on, the fan keeps going until it burns out or you have a flat battery (ask Ford why they had to recall so many Sierra Cosworths). Secondly, if you have a voltage drop alarm and the fan switches off after the arming delay it will set the alarm off.
Ivan
The bible gives the details of the various fan optuons and fittings. The 40 AMP single fuse was a temp fix that works most of the time but TVR modified the wiring so that each fan was seperately fused. A lot better.
Running the fans after the engine ios off is a waste of time. Their is no water circulation so that all that happens id the radiator water cools down. When the engine starts up again, the cold water will flow in to the hot engine and cause a higher degress of thermal shock.
If the fans are coming on and the indicated temp is not going down... then something is wrong! As in there is a fault somewhere. Either the gauge is lying or there is some other problem that is causing the issue like a blocked rad, duff water pump, low coolent level, air lock. Trying to get more fan cooling is trying to cover the symptom rather than find the original fault.
Steve
www.tvrbooks.co.uk
Running the fans after the engine ios off is a waste of time. Their is no water circulation so that all that happens id the radiator water cools down. When the engine starts up again, the cold water will flow in to the hot engine and cause a higher degress of thermal shock.
If the fans are coming on and the indicated temp is not going down... then something is wrong! As in there is a fault somewhere. Either the gauge is lying or there is some other problem that is causing the issue like a blocked rad, duff water pump, low coolent level, air lock. Trying to get more fan cooling is trying to cover the symptom rather than find the original fault.
Steve
www.tvrbooks.co.uk
I guess we all have our funny ways.Of course my original system was just fine, or was that, fine just! I like my fans to continue to expell the hot air from under the bonnet for just a few minutes and i rewired so i had some extra cooling available for those nervous sits in traffic. I didnt actually have a problem. But i agree if there is a problem this isnt the way to sort it.
i think that its normal for the temp to just stay stable in hot traffic conditions on these cars from my experience.if the temp gauge moves down at all,it isnt by much before the fans turn off.my own opinion on this is it occurs due to the poor location of the otter switch and its being affected by manifold temp and then by the air blown over it from when the fans are on.the otter switch should be located on the radiator outlet.i recalled seeing an inline hose insert with an otter type switch fitted many years ago,and have recently found a source-demon tweeks.fitting one of these to radiator outlet hose would mean your fans coming on at correct temp everytime,and they should then stay on until ingoing water supply to engine reaches required lower temp.i still think its a great idea to seperate fan power supplys though,as the extra fan speed can only be usefull but also because i suffered a burnt out fuseboard on my old chim caused by overloaded fan supply.this also burnt relays,battery and worst of all the flames burnt the heater box above!-total cost was £1400 and its only costing me £9 to modify this-well worth it!
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