Phil6 Posted May 24, 2020 Report Share Posted May 24, 2020 Hi, I have fitted a revotec fan and it works fine for about 300 miles then the indicators, temperature gauge and fuel gauge went off which I traced to the 20 amp fuse I had connected the fan to had blown, so the fan only runs with ignition on. When I-replaced the fuse all is fine again but I noticed the fuse is getting very hot when the fan is running. Does anyone have any alternative suggestions where to wire this fan to? Many thanks. Phil. Quote Link to post Share on other sites
Bleednipple Posted May 24, 2020 Report Share Posted May 24, 2020 I had this problem where my fan (an old Kenlowe, not a Revotec) kept blowing ever-bigger fuses - I got up to a 25 amp. The problem turned out to be the poor quality add-on fuse boxes in my car - repro MGB-type boxes - that just weren't up to the job. Fans do of course tend to draw very big start-up currents. The temp solution was to bypass the fuse box and inset a modern blade fuse, in line, for the fan. Longer term I will upgrade all the fusing to modern kit, and to hell with any attempt at originality, it just needs to work reliably. I'm not any kind of electrician so you'll probably get a better answer from someone else if they read this. Nigel Quote Link to post Share on other sites
RobH Posted May 24, 2020 Report Share Posted May 24, 2020 The fan must be pulling quite a current and if this is coming via one of the standard fuses which supplies other circuits too it is maybe no surprise that it gets hot. If the clip that holds the fuse is weak or dirty it may be resistive and the fuse itself also will have resistance. There may be enough total resistance to produce some appreciable heat - 20 Amps through 0.1 Ohm is 40 watts which has to go somewhere. As Nigel says a dedicated low resistance fuse for the fan alone is a good idea and wire it through a relay direct to the battery feed so the ignition switch does not have to carry that current, but rather just the relay coil current. Quote Link to post Share on other sites
Phil6 Posted May 24, 2020 Author Report Share Posted May 24, 2020 Thanks for your replies. So if I take a supply from the input to the existing fuse to a new 30 amp fuse then to the relay for the fan will that work ok? Phil. Quote Link to post Share on other sites
RobH Posted May 24, 2020 Report Share Posted May 24, 2020 It will work Phil but that would still mean the current comes via the ignition switch, which is not a good idea as it overloads the switch. You can use the existing feed point for the coil of a relay so that it switches power to the fan circuit when the ignition is on, but you need to take a separate 30A fused feed from the non-battery end of the ammeter and through the relay contacts to the fan itself, so your existing fan feed connects to terminal 87 on the relay. This is the simple way to do it using your existing fan control arrangement. Quote Link to post Share on other sites
Lebro Posted May 25, 2020 Report Share Posted May 25, 2020 +1 Bob. Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 15 hours ago, RobH said: It will work Phil but that would still mean the current comes via the ignition switch, which is not a good idea as it overloads the switch. You can use the existing feed point for the coil of a relay so that it switches power to the fan circuit when the ignition is on, but you need to take a separate 30A fused feed from the non-battery end of the ammeter and through the relay contacts to the fan itself, so your existing fan feed connects to terminal 87 on the relay. This is the simple way to do it using your existing fan control arrangement. Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 Thanks for this Rob, I am still a little confused, is the feed from the non battery side of the ammeter supposed to be live all the time or only when the ignition is on? I have wired a feed to what I think is the non battery side which goes to the alternator according to the wiring diagram but this is live all the time with the ignition on or off, the wire is brown and white. The other wire is brown and according to the wiring diagram goes to the battery. I also don’t understand what you mean about the original feed as there is only one live red wire and the earth wire to connect out of the relay. Hope Im not confusing you! Phil. Quote Link to post Share on other sites
RobH Posted May 25, 2020 Report Share Posted May 25, 2020 (edited) The feed to the relay pin 30 should be live all the time Phil. You didn't tell us what control system you have fitted for the fan. You must already have some sort of switch/thermostat arrangement for it which was connected to the fuse that blew - presumably by your red wire. You just connect that wire to the relay pin 87 instead. The relay pin 86 is connected to that original fuse so the relay gets switched on whenever the ignition is on. The system should work exactly as it did before except the high current is supplied via the relay and not by the ignition switch. Edited May 25, 2020 by RobH Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 Ok it works fine off the ammeter only problem is the fan keeps running when ignition is turned off and won’t stop till temperature reduces. so if I want it to turnoff with ignition does it have to be via ignition switch? Ive attached a couple of pictures Quote Link to post Share on other sites
RobH Posted May 25, 2020 Report Share Posted May 25, 2020 (edited) If you wired it up as I drew it that cannot happen Phil. (sorry this reply has taken some time as I had to amend the drawing) If the red wire goes to the normally open contacts of a new additional relay using the numbers I gave you, there will be no power to the fan control circuit until the ignition is switched on and the fan will stop as soon as the ignition is switched off. (Note that there may be two terminals on the new relay numbered 87 and 87a. You must use 87. ) This is what I meant: It might be possible to do it with the relay you have but if it is sealed and you can't get at the wiring, this way is easiest and saves modifiying anything. Edited May 25, 2020 by RobH Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 Ah I get it now your saying I need an additional relay to make it work that way. The relay I have is a sealed unit from the factory with the wires to the fan attached to a plug which is in turn plugged into the relay with a seal on it saying void if removed. as you probably guessed I’m no electrician. Phil. Quote Link to post Share on other sites
RobH Posted May 25, 2020 Report Share Posted May 25, 2020 No problem Phil - you can probably get a suitable relay and fuse-holder at Halfords to do the additions. I hope the drawing above makes it clearer. Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 Thanks so much for your help Rob you’ve been great. Ive put a photo of the relay supplied here. Regards. Phil. Quote Link to post Share on other sites
rvwp Posted May 25, 2020 Report Share Posted May 25, 2020 Hi all, As I am about to buy and fit a Revotec electric fan, I am very interested in this topic. One question that as probably been asked before on the Forum, having uprated to a narrow fan belt and therefore no longer have an original fan fitted, which is best, pulling or pushing? Also is there an adaptor available that allows an original style fan to be fitted to the narrow belt crank pulley so that the electric fan is supplementary, or is that not necessary? Thanks Rich Quote Link to post Share on other sites
Bleednipple Posted May 25, 2020 Report Share Posted May 25, 2020 43 minutes ago, rvwp said: Hi all, As I am about to buy and fit a Revotec electric fan, I am very interested in this topic. One question that as probably been asked before on the Forum, having uprated to a narrow fan belt and therefore no longer have an original fan fitted, which is best, pulling or pushing? Also is there an adaptor available that allows an original style fan to be fitted to the narrow belt crank pulley so that the electric fan is supplementary, or is that not necessary? Thanks Rich A puller (ie mounted on the engine side of the rad) is generally regarded as much better than a pusher if you have the option, because a puller doesn't impede the airflow to the radiator core. How much difference it actually makes in practice, I don't know. Aside from that, a question to ponder is whether a puller fan contributes to, or reduces, under-bonnet temperature, which is a big issue when pressing any car hard. I was told one degree of 'excess' under bonnet temp robs 1 bhp although have no data to back that up. Nigel Quote Link to post Share on other sites
Phil6 Posted May 25, 2020 Author Report Share Posted May 25, 2020 Hi, if you buy the Revotec as I did it’s definitely better behind the radiator and that said the original fan has to be removed and the kit has a new boss which bolts the belt pulley on. There is definitely no room left for a mechanical fan and I would say it’s not required, the electric fan pulls the temperature down very quickly. Hope this helps. Phil. Quote Link to post Share on other sites
Quicksilver Posted May 25, 2020 Report Share Posted May 25, 2020 Hi Phil, I think it is no problem that the fan is cooling (thermo switch)when the ignition is off. It stops when the temperature is cooling down. Normally the temperature rise when you stop the car and stop the engine, so when the fan kicks in, the cooling starts also for the engine compartment and blow away the hot air. Marcel. Quote Link to post Share on other sites
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